Add support for binding with a custom marshal/unmarshal function (#104)

## Summary:
This is useful if you want to bind to a type you don't control (or use
for other things) but need different serialization than its default.
This is a feature gqlgen has and we've found it very useful.  For
example, in webapp we want to bind `DateTime` to `time.Time`, but its
default serialization is not compatible with Python, so currently we
have to bind to a wrapper type and cast all over the place, which is
exactly the sort of boilerplate genqlient is supposed to avoid.

For unmarshaling, the implementation basically just follows the existing
support for abstract types; instead of calling our own generated
helper, we now call your specified function.  This required some
refactoring to abstract the handling of custom unmarshalers generally
from abstract types specifically, and to wire in not only the
unmarshaler-name but also the `generator` (in order to compute the right
import alias).

For marshaling, I had to implement all that stuff over again; it's
mostly parallel to unmarshaling (and I made a few minor changes to
unmarshaling to make the two more parallel).  Luckily, after #103 I at
least only had to do it once, rather than implementing the same
functionality for arguments and for input-type fields.  It was still
quite a bit of code; I didn't try to be quite as completionist about the
tests as with unmarshal but still had to add a few.

Issue: https://github.com/Khan/genqlient/issues/38

## Test plan:
make check


Author: benjaminjkraft

Reviewers: StevenACoffman, dnerdy, benjaminjkraft, aberkan, jvoll, mahtabsabet, MiguelCastillo

Required Reviewers: 

Approved By: StevenACoffman, dnerdy

Checks: ✅ Test (1.17), ✅ Test (1.16), ✅ Test (1.15), ✅ Test (1.14), ✅ Lint, ✅ Test (1.17), ✅ Test (1.16), ✅ Test (1.15), ✅ Test (1.14), ✅ Lint

Pull Request URL: https://github.com/Khan/genqlient/pull/104

generate/testdata/queries/CustomMarshal.graphql

@@ -0,0 +1,6 @@
+query CustomMarshal($date: Date!) {
+  usersBornOn(date: $date) {
+    id
+    birthdate
+  }
+}

generate/testdata/queries/CustomMarshalSlice.graphql

@@ -0,0 +1,8 @@
+query CustomMarshalSlice(
+  $datesss: [[[Date!]!]!]!,
+  # @genqlient(pointer: true)
+  $datesssp: [[[Date!]!]!]!,
+) {
+  acceptsListOfListOfListsOfDates(datesss: $datesss)
+  withPointer: acceptsListOfListOfListsOfDates(datesss: $datesssp)
+}

generate/testdata/queries/schema.graphql

@@ -3,6 +3,7 @@
 We don't really have anything useful to do with this description though.
 """
 scalar DateTime
+scalar Date
 scalar Junk
 scalar ComplexJunk
 
@@ -44,6 +45,7 @@ input UserQueryInput {
   role: Role
   names: [String]
   hasPokemon: PokemonInput
+  birthdate: Date
 }
 
 type AuthMethod {
@@ -66,6 +68,7 @@ type User {
   authMethods: [AuthMethod!]!
   pokemon: [Pokemon!]
   greeting: Clip
+  birthdate: Date
 }
 
 """An audio clip, such as of a user saying hello."""
@@ -153,6 +156,9 @@ type Query {
 
   """usersWithRole looks a user up by role."""
   usersWithRole(role: Role!): [User!]!
+
+  usersBornOn(date: Date!): [User!]!
+
   root: Topic!
   randomItem: Content!
   randomLeaf: LeafContent!
@@ -163,6 +169,7 @@ type Query {
   listOfListsOfLists: [[[String!]!]!]!
   listOfListsOfListsOfContent: [[[Content!]!]!]!
   recur(input: RecursiveInput!): Recursive
+  acceptsListOfListOfListsOfDates(datesss: [[[Date!]!]!]!): Boolean
 }
 
 type Mutation {

generate/testdata/snapshots/TestGenerate-ComplexInlineFragments.graphql-ComplexInlineFragments.graphql.go

@@ -55,15 +55,15 @@ func (v *ComplexInlineFragmentsConflictingStuffTopic) implementsGraphQLInterface
 // GetTypename is a part of, and documented with, the interface ComplexInlineFragmentsConflictingStuffContent.
 func (v *ComplexInlineFragmentsConflictingStuffTopic) GetTypename() string { return v.Typename }
 
-func __unmarshalComplexInlineFragmentsConflictingStuffContent(v *ComplexInlineFragmentsConflictingStuffContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalComplexInlineFragmentsConflictingStuffContent(b []byte, v *ComplexInlineFragmentsConflictingStuffContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -71,13 +71,13 @@ func __unmarshalComplexInlineFragmentsConflictingStuffContent(v *ComplexInlineFr
 	switch tn.TypeName {
 	case "Article":
 		*v = new(ComplexInlineFragmentsConflictingStuffArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(ComplexInlineFragmentsConflictingStuffVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(ComplexInlineFragmentsConflictingStuffTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -142,15 +142,15 @@ func (v *ComplexInlineFragmentsNestedStuffTopic) implementsGraphQLInterfaceCompl
 // GetTypename is a part of, and documented with, the interface ComplexInlineFragmentsNestedStuffContent.
 func (v *ComplexInlineFragmentsNestedStuffTopic) GetTypename() string { return v.Typename }
 
-func __unmarshalComplexInlineFragmentsNestedStuffContent(v *ComplexInlineFragmentsNestedStuffContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalComplexInlineFragmentsNestedStuffContent(b []byte, v *ComplexInlineFragmentsNestedStuffContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -158,13 +158,13 @@ func __unmarshalComplexInlineFragmentsNestedStuffContent(v *ComplexInlineFragmen
 	switch tn.TypeName {
 	case "Article":
 		*v = new(ComplexInlineFragmentsNestedStuffArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(ComplexInlineFragmentsNestedStuffVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(ComplexInlineFragmentsNestedStuffTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -182,6 +182,10 @@ type ComplexInlineFragmentsNestedStuffTopic struct {
 
 func (v *ComplexInlineFragmentsNestedStuffTopic) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*ComplexInlineFragmentsNestedStuffTopic
 		Children []json.RawMessage `json:"children"`
@@ -195,15 +199,15 @@ func (v *ComplexInlineFragmentsNestedStuffTopic) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.Children
-		raw := firstPass.Children
-		*target = make(
+		dst := &v.Children
+		src := firstPass.Children
+		*dst = make(
 			[]ComplexInlineFragmentsNestedStuffTopicChildrenContent,
-			len(raw))
-		for i, raw := range raw {
-			target := &(*target)[i]
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
 			err = __unmarshalComplexInlineFragmentsNestedStuffTopicChildrenContent(
-				target, raw)
+				src, dst)
 			if err != nil {
 				return fmt.Errorf(
 					"Unable to unmarshal ComplexInlineFragmentsNestedStuffTopic.Children: %w", err)
@@ -229,6 +233,10 @@ type ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTop
 
 func (v *ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopic) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopic
 		Children []json.RawMessage `json:"children"`
@@ -242,15 +250,15 @@ func (v *ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParen
 	}
 
 	{
-		target := &v.Children
-		raw := firstPass.Children
-		*target = make(
+		dst := &v.Children
+		src := firstPass.Children
+		*dst = make(
 			[]ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopicChildrenContent,
-			len(raw))
-		for i, raw := range raw {
-			target := &(*target)[i]
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
 			err = __unmarshalComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopicChildrenContent(
-				target, raw)
+				src, dst)
 			if err != nil {
 				return fmt.Errorf(
 					"Unable to unmarshal ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopic.Children: %w", err)
@@ -344,15 +352,15 @@ func (v *ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParen
 	return v.Name
 }
 
-func __unmarshalComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopicChildrenContent(v *ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopicChildrenContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopicChildrenContent(b []byte, v *ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopicChildrenContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -360,13 +368,13 @@ func __unmarshalComplexInlineFragmentsNestedStuffTopicChildrenArticleParentConte
 	switch tn.TypeName {
 	case "Article":
 		*v = new(ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopicChildrenArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopicChildrenVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(ComplexInlineFragmentsNestedStuffTopicChildrenArticleParentContentParentTopicChildrenTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -447,15 +455,15 @@ func (v *ComplexInlineFragmentsNestedStuffTopicChildrenTopic) GetTypename() stri
 // GetId is a part of, and documented with, the interface ComplexInlineFragmentsNestedStuffTopicChildrenContent.
 func (v *ComplexInlineFragmentsNestedStuffTopicChildrenTopic) GetId() testutil.ID { return v.Id }
 
-func __unmarshalComplexInlineFragmentsNestedStuffTopicChildrenContent(v *ComplexInlineFragmentsNestedStuffTopicChildrenContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalComplexInlineFragmentsNestedStuffTopicChildrenContent(b []byte, v *ComplexInlineFragmentsNestedStuffTopicChildrenContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -463,13 +471,13 @@ func __unmarshalComplexInlineFragmentsNestedStuffTopicChildrenContent(v *Complex
 	switch tn.TypeName {
 	case "Article":
 		*v = new(ComplexInlineFragmentsNestedStuffTopicChildrenArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(ComplexInlineFragmentsNestedStuffTopicChildrenVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(ComplexInlineFragmentsNestedStuffTopicChildrenTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -565,15 +573,15 @@ func (v *ComplexInlineFragmentsRandomItemTopic) GetId() testutil.ID { return v.I
 // GetName is a part of, and documented with, the interface ComplexInlineFragmentsRandomItemContent.
 func (v *ComplexInlineFragmentsRandomItemTopic) GetName() string { return v.Name }
 
-func __unmarshalComplexInlineFragmentsRandomItemContent(v *ComplexInlineFragmentsRandomItemContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalComplexInlineFragmentsRandomItemContent(b []byte, v *ComplexInlineFragmentsRandomItemContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -581,13 +589,13 @@ func __unmarshalComplexInlineFragmentsRandomItemContent(v *ComplexInlineFragment
 	switch tn.TypeName {
 	case "Article":
 		*v = new(ComplexInlineFragmentsRandomItemArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(ComplexInlineFragmentsRandomItemVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(ComplexInlineFragmentsRandomItemTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -721,15 +729,15 @@ func (v *ComplexInlineFragmentsRepeatedStuffTopic) GetName() string { return v.N
 // GetOtherName is a part of, and documented with, the interface ComplexInlineFragmentsRepeatedStuffContent.
 func (v *ComplexInlineFragmentsRepeatedStuffTopic) GetOtherName() string { return v.OtherName }
 
-func __unmarshalComplexInlineFragmentsRepeatedStuffContent(v *ComplexInlineFragmentsRepeatedStuffContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalComplexInlineFragmentsRepeatedStuffContent(b []byte, v *ComplexInlineFragmentsRepeatedStuffContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -737,13 +745,13 @@ func __unmarshalComplexInlineFragmentsRepeatedStuffContent(v *ComplexInlineFragm
 	switch tn.TypeName {
 	case "Article":
 		*v = new(ComplexInlineFragmentsRepeatedStuffArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(ComplexInlineFragmentsRepeatedStuffVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(ComplexInlineFragmentsRepeatedStuffTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -789,6 +797,10 @@ type ComplexInlineFragmentsResponse struct {
 
 func (v *ComplexInlineFragmentsResponse) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*ComplexInlineFragmentsResponse
 		RandomItem       json.RawMessage `json:"randomItem"`
@@ -805,10 +817,10 @@ func (v *ComplexInlineFragmentsResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RandomItem
-		raw := firstPass.RandomItem
+		dst := &v.RandomItem
+		src := firstPass.RandomItem
 		err = __unmarshalComplexInlineFragmentsRandomItemContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal ComplexInlineFragmentsResponse.RandomItem: %w", err)
@@ -816,10 +828,10 @@ func (v *ComplexInlineFragmentsResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RepeatedStuff
-		raw := firstPass.RepeatedStuff
+		dst := &v.RepeatedStuff
+		src := firstPass.RepeatedStuff
 		err = __unmarshalComplexInlineFragmentsRepeatedStuffContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal ComplexInlineFragmentsResponse.RepeatedStuff: %w", err)
@@ -827,10 +839,10 @@ func (v *ComplexInlineFragmentsResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.ConflictingStuff
-		raw := firstPass.ConflictingStuff
+		dst := &v.ConflictingStuff
+		src := firstPass.ConflictingStuff
 		err = __unmarshalComplexInlineFragmentsConflictingStuffContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal ComplexInlineFragmentsResponse.ConflictingStuff: %w", err)
@@ -838,10 +850,10 @@ func (v *ComplexInlineFragmentsResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.NestedStuff
-		raw := firstPass.NestedStuff
+		dst := &v.NestedStuff
+		src := firstPass.NestedStuff
 		err = __unmarshalComplexInlineFragmentsNestedStuffContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal ComplexInlineFragmentsResponse.NestedStuff: %w", err)

generate/testdata/snapshots/TestGenerate-ComplexNamedFragments.graphql-ComplexNamedFragments.graphql.go

@@ -17,6 +17,10 @@ type ComplexNamedFragmentsResponse struct {
 
 func (v *ComplexNamedFragmentsResponse) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*ComplexNamedFragmentsResponse
 		graphql.NoUnmarshalJSON
@@ -77,15 +81,15 @@ func (v *ContentFieldsTopic) GetName() string { return v.Name }
 // GetUrl is a part of, and documented with, the interface ContentFields.
 func (v *ContentFieldsTopic) GetUrl() string { return v.Url }
 
-func __unmarshalContentFields(v *ContentFields, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalContentFields(b []byte, v *ContentFields) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -93,13 +97,13 @@ func __unmarshalContentFields(v *ContentFields, m json.RawMessage) error {
 	switch tn.TypeName {
 	case "Article":
 		*v = new(ContentFieldsArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(ContentFieldsVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(ContentFieldsTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -148,6 +152,10 @@ type InnerQueryFragment struct {
 
 func (v *InnerQueryFragment) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InnerQueryFragment
 		RandomItem json.RawMessage `json:"randomItem"`
@@ -163,10 +171,10 @@ func (v *InnerQueryFragment) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RandomItem
-		raw := firstPass.RandomItem
+		dst := &v.RandomItem
+		src := firstPass.RandomItem
 		err = __unmarshalInnerQueryFragmentRandomItemContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal InnerQueryFragment.RandomItem: %w", err)
@@ -174,10 +182,10 @@ func (v *InnerQueryFragment) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RandomLeaf
-		raw := firstPass.RandomLeaf
+		dst := &v.RandomLeaf
+		src := firstPass.RandomLeaf
 		err = __unmarshalInnerQueryFragmentRandomLeafLeafContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal InnerQueryFragment.RandomLeaf: %w", err)
@@ -185,10 +193,10 @@ func (v *InnerQueryFragment) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.OtherLeaf
-		raw := firstPass.OtherLeaf
+		dst := &v.OtherLeaf
+		src := firstPass.OtherLeaf
 		err = __unmarshalInnerQueryFragmentOtherLeafLeafContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal InnerQueryFragment.OtherLeaf: %w", err)
@@ -205,6 +213,10 @@ type InnerQueryFragmentOtherLeafArticle struct {
 
 func (v *InnerQueryFragmentOtherLeafArticle) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InnerQueryFragmentOtherLeafArticle
 		graphql.NoUnmarshalJSON
@@ -250,15 +262,15 @@ func (v *InnerQueryFragmentOtherLeafVideo) implementsGraphQLInterfaceInnerQueryF
 // GetTypename is a part of, and documented with, the interface InnerQueryFragmentOtherLeafLeafContent.
 func (v *InnerQueryFragmentOtherLeafVideo) GetTypename() string { return v.Typename }
 
-func __unmarshalInnerQueryFragmentOtherLeafLeafContent(v *InnerQueryFragmentOtherLeafLeafContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInnerQueryFragmentOtherLeafLeafContent(b []byte, v *InnerQueryFragmentOtherLeafLeafContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -266,10 +278,10 @@ func __unmarshalInnerQueryFragmentOtherLeafLeafContent(v *InnerQueryFragmentOthe
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InnerQueryFragmentOtherLeafArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InnerQueryFragmentOtherLeafVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing LeafContent.__typename")
@@ -288,6 +300,10 @@ type InnerQueryFragmentOtherLeafVideo struct {
 
 func (v *InnerQueryFragmentOtherLeafVideo) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InnerQueryFragmentOtherLeafVideo
 		graphql.NoUnmarshalJSON
@@ -323,6 +339,10 @@ type InnerQueryFragmentRandomItemArticle struct {
 
 func (v *InnerQueryFragmentRandomItemArticle) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InnerQueryFragmentRandomItemArticle
 		graphql.NoUnmarshalJSON
@@ -401,15 +421,15 @@ func (v *InnerQueryFragmentRandomItemTopic) GetId() testutil.ID { return v.Id }
 // GetName is a part of, and documented with, the interface InnerQueryFragmentRandomItemContent.
 func (v *InnerQueryFragmentRandomItemTopic) GetName() string { return v.Name }
 
-func __unmarshalInnerQueryFragmentRandomItemContent(v *InnerQueryFragmentRandomItemContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInnerQueryFragmentRandomItemContent(b []byte, v *InnerQueryFragmentRandomItemContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -417,13 +437,13 @@ func __unmarshalInnerQueryFragmentRandomItemContent(v *InnerQueryFragmentRandomI
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InnerQueryFragmentRandomItemArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InnerQueryFragmentRandomItemVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(InnerQueryFragmentRandomItemTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -444,6 +464,10 @@ type InnerQueryFragmentRandomItemTopic struct {
 
 func (v *InnerQueryFragmentRandomItemTopic) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InnerQueryFragmentRandomItemTopic
 		graphql.NoUnmarshalJSON
@@ -475,6 +499,10 @@ type InnerQueryFragmentRandomItemVideo struct {
 
 func (v *InnerQueryFragmentRandomItemVideo) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InnerQueryFragmentRandomItemVideo
 		graphql.NoUnmarshalJSON
@@ -507,6 +535,10 @@ type InnerQueryFragmentRandomLeafArticle struct {
 
 func (v *InnerQueryFragmentRandomLeafArticle) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InnerQueryFragmentRandomLeafArticle
 		graphql.NoUnmarshalJSON
@@ -552,15 +584,15 @@ func (v *InnerQueryFragmentRandomLeafVideo) implementsGraphQLInterfaceInnerQuery
 // GetTypename is a part of, and documented with, the interface InnerQueryFragmentRandomLeafLeafContent.
 func (v *InnerQueryFragmentRandomLeafVideo) GetTypename() string { return v.Typename }
 
-func __unmarshalInnerQueryFragmentRandomLeafLeafContent(v *InnerQueryFragmentRandomLeafLeafContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInnerQueryFragmentRandomLeafLeafContent(b []byte, v *InnerQueryFragmentRandomLeafLeafContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -568,10 +600,10 @@ func __unmarshalInnerQueryFragmentRandomLeafLeafContent(v *InnerQueryFragmentRan
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InnerQueryFragmentRandomLeafArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InnerQueryFragmentRandomLeafVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing LeafContent.__typename")
@@ -591,6 +623,10 @@ type InnerQueryFragmentRandomLeafVideo struct {
 
 func (v *InnerQueryFragmentRandomLeafVideo) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InnerQueryFragmentRandomLeafVideo
 		graphql.NoUnmarshalJSON
@@ -637,6 +673,10 @@ type MoreVideoFieldsParentTopic struct {
 
 func (v *MoreVideoFieldsParentTopic) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*MoreVideoFieldsParentTopic
 		Children []json.RawMessage `json:"children"`
@@ -656,15 +696,15 @@ func (v *MoreVideoFieldsParentTopic) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.Children
-		raw := firstPass.Children
-		*target = make(
+		dst := &v.Children
+		src := firstPass.Children
+		*dst = make(
 			[]MoreVideoFieldsParentTopicChildrenContent,
-			len(raw))
-		for i, raw := range raw {
-			target := &(*target)[i]
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
 			err = __unmarshalMoreVideoFieldsParentTopicChildrenContent(
-				target, raw)
+				src, dst)
 			if err != nil {
 				return fmt.Errorf(
 					"Unable to unmarshal MoreVideoFieldsParentTopic.Children: %w", err)
@@ -712,15 +752,15 @@ func (v *MoreVideoFieldsParentTopicChildrenTopic) implementsGraphQLInterfaceMore
 // GetTypename is a part of, and documented with, the interface MoreVideoFieldsParentTopicChildrenContent.
 func (v *MoreVideoFieldsParentTopicChildrenTopic) GetTypename() *string { return v.Typename }
 
-func __unmarshalMoreVideoFieldsParentTopicChildrenContent(v *MoreVideoFieldsParentTopicChildrenContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalMoreVideoFieldsParentTopicChildrenContent(b []byte, v *MoreVideoFieldsParentTopicChildrenContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -728,13 +768,13 @@ func __unmarshalMoreVideoFieldsParentTopicChildrenContent(v *MoreVideoFieldsPare
 	switch tn.TypeName {
 	case "Article":
 		*v = new(MoreVideoFieldsParentTopicChildrenArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(MoreVideoFieldsParentTopicChildrenVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(MoreVideoFieldsParentTopicChildrenTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -757,6 +797,10 @@ type MoreVideoFieldsParentTopicChildrenVideo struct {
 
 func (v *MoreVideoFieldsParentTopicChildrenVideo) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*MoreVideoFieldsParentTopicChildrenVideo
 		graphql.NoUnmarshalJSON
@@ -786,6 +830,10 @@ type QueryFragment struct {
 
 func (v *QueryFragment) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*QueryFragment
 		graphql.NoUnmarshalJSON
@@ -818,6 +866,10 @@ type VideoFields struct {
 
 func (v *VideoFields) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*VideoFields
 		graphql.NoUnmarshalJSON

generate/testdata/snapshots/TestGenerate-CustomMarshal.graphql-CustomMarshal.graphql.go

@@ -0,0 +1,118 @@
+package test
+
+// Code generated by github.com/Khan/genqlient, DO NOT EDIT.
+
+import (
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"github.com/Khan/genqlient/graphql"
+	"github.com/Khan/genqlient/internal/testutil"
+)
+
+// CustomMarshalResponse is returned by CustomMarshal on success.
+type CustomMarshalResponse struct {
+	UsersBornOn []CustomMarshalUsersBornOnUser `json:"usersBornOn"`
+}
+
+// CustomMarshalUsersBornOnUser includes the requested fields of the GraphQL type User.
+// The GraphQL type's documentation follows.
+//
+// A User is a user!
+type CustomMarshalUsersBornOnUser struct {
+	// id is the user's ID.
+	//
+	// It is stable, unique, and opaque, like all good IDs.
+	Id        testutil.ID `json:"id"`
+	Birthdate time.Time   `json:"-"`
+}
+
+func (v *CustomMarshalUsersBornOnUser) UnmarshalJSON(b []byte) error {
+
+	if string(b) == "null" {
+		return nil
+	}
+
+	var firstPass struct {
+		*CustomMarshalUsersBornOnUser
+		Birthdate json.RawMessage `json:"birthdate"`
+		graphql.NoUnmarshalJSON
+	}
+	firstPass.CustomMarshalUsersBornOnUser = v
+
+	err := json.Unmarshal(b, &firstPass)
+	if err != nil {
+		return err
+	}
+
+	{
+		dst := &v.Birthdate
+		src := firstPass.Birthdate
+		err = testutil.UnmarshalDate(
+			src, dst)
+		if err != nil {
+			return fmt.Errorf(
+				"Unable to unmarshal CustomMarshalUsersBornOnUser.Birthdate: %w", err)
+		}
+	}
+	return nil
+}
+
+// __CustomMarshalInput is used internally by genqlient
+type __CustomMarshalInput struct {
+	Date time.Time `json:"-"`
+}
+
+func (v *__CustomMarshalInput) MarshalJSON() ([]byte, error) {
+
+	var fullObject struct {
+		*__CustomMarshalInput
+		Date json.RawMessage `json:"date"`
+		graphql.NoMarshalJSON
+	}
+	fullObject.__CustomMarshalInput = v
+
+	{
+
+		dst := &fullObject.Date
+		src := v.Date
+		var err error
+		*dst, err = testutil.MarshalDate(
+			&src)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"Unable to marshal __CustomMarshalInput.Date: %w", err)
+		}
+	}
+
+	return json.Marshal(&fullObject)
+}
+
+func CustomMarshal(
+	client graphql.Client,
+	date time.Time,
+) (*CustomMarshalResponse, error) {
+	__input := __CustomMarshalInput{
+		Date: date,
+	}
+	var err error
+
+	var retval CustomMarshalResponse
+	err = client.MakeRequest(
+		nil,
+		"CustomMarshal",
+		`
+query CustomMarshal ($date: Date!) {
+	usersBornOn(date: $date) {
+		id
+		birthdate
+	}
+}
+`,
+		&retval,
+		&__input,
+	)
+	return &retval, err
+}
+

generate/testdata/snapshots/TestGenerate-CustomMarshal.graphql-CustomMarshal.graphql.json

@@ -0,0 +1,9 @@
+{
+  "operations": [
+    {
+      "operationName": "CustomMarshal",
+      "query": "\nquery CustomMarshal ($date: Date!) {\n\tusersBornOn(date: $date) {\n\t\tid\n\t\tbirthdate\n\t}\n}\n",
+      "sourceLocation": "testdata/queries/CustomMarshal.graphql"
+    }
+  ]
+}

generate/testdata/snapshots/TestGenerate-CustomMarshalSlice.graphql-CustomMarshalSlice.graphql.go

@@ -0,0 +1,126 @@
+package test
+
+// Code generated by github.com/Khan/genqlient, DO NOT EDIT.
+
+import (
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"github.com/Khan/genqlient/graphql"
+	"github.com/Khan/genqlient/internal/testutil"
+)
+
+// CustomMarshalSliceResponse is returned by CustomMarshalSlice on success.
+type CustomMarshalSliceResponse struct {
+	AcceptsListOfListOfListsOfDates bool `json:"acceptsListOfListOfListsOfDates"`
+	WithPointer                     bool `json:"withPointer"`
+}
+
+// __CustomMarshalSliceInput is used internally by genqlient
+type __CustomMarshalSliceInput struct {
+	Datesss  [][][]time.Time  `json:"-"`
+	Datesssp [][][]*time.Time `json:"-"`
+}
+
+func (v *__CustomMarshalSliceInput) MarshalJSON() ([]byte, error) {
+
+	var fullObject struct {
+		*__CustomMarshalSliceInput
+		Datesss  [][][]json.RawMessage `json:"datesss"`
+		Datesssp [][][]json.RawMessage `json:"datesssp"`
+		graphql.NoMarshalJSON
+	}
+	fullObject.__CustomMarshalSliceInput = v
+
+	{
+
+		dst := &fullObject.Datesss
+		src := v.Datesss
+		*dst = make(
+			[][][]json.RawMessage,
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
+			*dst = make(
+				[][]json.RawMessage,
+				len(src))
+			for i, src := range src {
+				dst := &(*dst)[i]
+				*dst = make(
+					[]json.RawMessage,
+					len(src))
+				for i, src := range src {
+					dst := &(*dst)[i]
+					var err error
+					*dst, err = testutil.MarshalDate(
+						&src)
+					if err != nil {
+						return nil, fmt.Errorf(
+							"Unable to marshal __CustomMarshalSliceInput.Datesss: %w", err)
+					}
+				}
+			}
+		}
+	}
+	{
+
+		dst := &fullObject.Datesssp
+		src := v.Datesssp
+		*dst = make(
+			[][][]json.RawMessage,
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
+			*dst = make(
+				[][]json.RawMessage,
+				len(src))
+			for i, src := range src {
+				dst := &(*dst)[i]
+				*dst = make(
+					[]json.RawMessage,
+					len(src))
+				for i, src := range src {
+					dst := &(*dst)[i]
+					var err error
+					*dst, err = testutil.MarshalDate(
+						src)
+					if err != nil {
+						return nil, fmt.Errorf(
+							"Unable to marshal __CustomMarshalSliceInput.Datesssp: %w", err)
+					}
+				}
+			}
+		}
+	}
+
+	return json.Marshal(&fullObject)
+}
+
+func CustomMarshalSlice(
+	client graphql.Client,
+	datesss [][][]time.Time,
+	datesssp [][][]*time.Time,
+) (*CustomMarshalSliceResponse, error) {
+	__input := __CustomMarshalSliceInput{
+		Datesss:  datesss,
+		Datesssp: datesssp,
+	}
+	var err error
+
+	var retval CustomMarshalSliceResponse
+	err = client.MakeRequest(
+		nil,
+		"CustomMarshalSlice",
+		`
+query CustomMarshalSlice ($datesss: [[[Date!]!]!]!, $datesssp: [[[Date!]!]!]!) {
+	acceptsListOfListOfListsOfDates(datesss: $datesss)
+	withPointer: acceptsListOfListOfListsOfDates(datesss: $datesssp)
+}
+`,
+		&retval,
+		&__input,
+	)
+	return &retval, err
+}
+

generate/testdata/snapshots/TestGenerate-CustomMarshalSlice.graphql-CustomMarshalSlice.graphql.json

@@ -0,0 +1,9 @@
+{
+  "operations": [
+    {
+      "operationName": "CustomMarshalSlice",
+      "query": "\nquery CustomMarshalSlice ($datesss: [[[Date!]!]!]!, $datesssp: [[[Date!]!]!]!) {\n\tacceptsListOfListOfListsOfDates(datesss: $datesss)\n\twithPointer: acceptsListOfListOfListsOfDates(datesss: $datesssp)\n}\n",
+      "sourceLocation": "testdata/queries/CustomMarshalSlice.graphql"
+    }
+  ]
+}

generate/testdata/snapshots/TestGenerate-InputObject.graphql-InputObject.graphql.go

@@ -3,6 +3,10 @@ package test
 // Code generated by github.com/Khan/genqlient, DO NOT EDIT.
 
 import (
+	"encoding/json"
+	"fmt"
+	"time"
+
 	"github.com/Khan/genqlient/graphql"
 	"github.com/Khan/genqlient/internal/testutil"
 )
@@ -54,6 +58,32 @@ type UserQueryInput struct {
 	Role       Role             `json:"role"`
 	Names      []string         `json:"names"`
 	HasPokemon testutil.Pokemon `json:"hasPokemon"`
+	Birthdate  time.Time        `json:"-"`
+}
+
+func (v *UserQueryInput) MarshalJSON() ([]byte, error) {
+
+	var fullObject struct {
+		*UserQueryInput
+		Birthdate json.RawMessage `json:"birthdate"`
+		graphql.NoMarshalJSON
+	}
+	fullObject.UserQueryInput = v
+
+	{
+
+		dst := &fullObject.Birthdate
+		src := v.Birthdate
+		var err error
+		*dst, err = testutil.MarshalDate(
+			&src)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"Unable to marshal UserQueryInput.Birthdate: %w", err)
+		}
+	}
+
+	return json.Marshal(&fullObject)
 }
 
 // __InputObjectQueryInput is used internally by genqlient

generate/testdata/snapshots/TestGenerate-InterfaceListField.graphql-InterfaceListField.graphql.go

@@ -26,6 +26,10 @@ type InterfaceListFieldRootTopic struct {
 
 func (v *InterfaceListFieldRootTopic) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InterfaceListFieldRootTopic
 		Children []json.RawMessage `json:"children"`
@@ -39,15 +43,15 @@ func (v *InterfaceListFieldRootTopic) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.Children
-		raw := firstPass.Children
-		*target = make(
+		dst := &v.Children
+		src := firstPass.Children
+		*dst = make(
 			[]InterfaceListFieldRootTopicChildrenContent,
-			len(raw))
-		for i, raw := range raw {
-			target := &(*target)[i]
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
 			err = __unmarshalInterfaceListFieldRootTopicChildrenContent(
-				target, raw)
+				src, dst)
 			if err != nil {
 				return fmt.Errorf(
 					"Unable to unmarshal InterfaceListFieldRootTopic.Children: %w", err)
@@ -123,15 +127,15 @@ func (v *InterfaceListFieldRootTopicChildrenTopic) GetId() testutil.ID { return
 // GetName is a part of, and documented with, the interface InterfaceListFieldRootTopicChildrenContent.
 func (v *InterfaceListFieldRootTopicChildrenTopic) GetName() string { return v.Name }
 
-func __unmarshalInterfaceListFieldRootTopicChildrenContent(v *InterfaceListFieldRootTopicChildrenContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInterfaceListFieldRootTopicChildrenContent(b []byte, v *InterfaceListFieldRootTopicChildrenContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -139,13 +143,13 @@ func __unmarshalInterfaceListFieldRootTopicChildrenContent(v *InterfaceListField
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InterfaceListFieldRootTopicChildrenArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InterfaceListFieldRootTopicChildrenVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(InterfaceListFieldRootTopicChildrenTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -181,6 +185,10 @@ type InterfaceListFieldWithPointerTopic struct {
 
 func (v *InterfaceListFieldWithPointerTopic) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InterfaceListFieldWithPointerTopic
 		Children []json.RawMessage `json:"children"`
@@ -194,15 +202,15 @@ func (v *InterfaceListFieldWithPointerTopic) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.Children
-		raw := firstPass.Children
-		*target = make(
+		dst := &v.Children
+		src := firstPass.Children
+		*dst = make(
 			[]InterfaceListFieldWithPointerTopicChildrenContent,
-			len(raw))
-		for i, raw := range raw {
-			target := &(*target)[i]
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
 			err = __unmarshalInterfaceListFieldWithPointerTopicChildrenContent(
-				target, raw)
+				src, dst)
 			if err != nil {
 				return fmt.Errorf(
 					"Unable to unmarshal InterfaceListFieldWithPointerTopic.Children: %w", err)
@@ -278,15 +286,15 @@ func (v *InterfaceListFieldWithPointerTopicChildrenTopic) GetId() testutil.ID {
 // GetName is a part of, and documented with, the interface InterfaceListFieldWithPointerTopicChildrenContent.
 func (v *InterfaceListFieldWithPointerTopicChildrenTopic) GetName() string { return v.Name }
 
-func __unmarshalInterfaceListFieldWithPointerTopicChildrenContent(v *InterfaceListFieldWithPointerTopicChildrenContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInterfaceListFieldWithPointerTopicChildrenContent(b []byte, v *InterfaceListFieldWithPointerTopicChildrenContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -294,13 +302,13 @@ func __unmarshalInterfaceListFieldWithPointerTopicChildrenContent(v *InterfaceLi
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InterfaceListFieldWithPointerTopicChildrenArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InterfaceListFieldWithPointerTopicChildrenVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(InterfaceListFieldWithPointerTopicChildrenTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")

generate/testdata/snapshots/TestGenerate-InterfaceListOfListsOfListsField.graphql-InterfaceListOfListsOfListsField.graphql.go

@@ -86,15 +86,15 @@ func (v *InterfaceListOfListOfListsFieldListOfListsOfListsOfContentTopic) GetNam
 	return v.Name
 }
 
-func __unmarshalInterfaceListOfListOfListsFieldListOfListsOfListsOfContent(v *InterfaceListOfListOfListsFieldListOfListsOfListsOfContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInterfaceListOfListOfListsFieldListOfListsOfListsOfContent(b []byte, v *InterfaceListOfListOfListsFieldListOfListsOfListsOfContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -102,13 +102,13 @@ func __unmarshalInterfaceListOfListOfListsFieldListOfListsOfListsOfContent(v *In
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InterfaceListOfListOfListsFieldListOfListsOfListsOfContentArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InterfaceListOfListOfListsFieldListOfListsOfListsOfContentVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(InterfaceListOfListOfListsFieldListOfListsOfListsOfContentTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -150,6 +150,10 @@ type InterfaceListOfListOfListsFieldResponse struct {
 
 func (v *InterfaceListOfListOfListsFieldResponse) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InterfaceListOfListOfListsFieldResponse
 		ListOfListsOfListsOfContent [][][]json.RawMessage `json:"listOfListsOfListsOfContent"`
@@ -164,25 +168,25 @@ func (v *InterfaceListOfListOfListsFieldResponse) UnmarshalJSON(b []byte) error
 	}
 
 	{
-		target := &v.ListOfListsOfListsOfContent
-		raw := firstPass.ListOfListsOfListsOfContent
-		*target = make(
+		dst := &v.ListOfListsOfListsOfContent
+		src := firstPass.ListOfListsOfListsOfContent
+		*dst = make(
 			[][][]InterfaceListOfListOfListsFieldListOfListsOfListsOfContent,
-			len(raw))
-		for i, raw := range raw {
-			target := &(*target)[i]
-			*target = make(
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
+			*dst = make(
 				[][]InterfaceListOfListOfListsFieldListOfListsOfListsOfContent,
-				len(raw))
-			for i, raw := range raw {
-				target := &(*target)[i]
-				*target = make(
+				len(src))
+			for i, src := range src {
+				dst := &(*dst)[i]
+				*dst = make(
 					[]InterfaceListOfListOfListsFieldListOfListsOfListsOfContent,
-					len(raw))
-				for i, raw := range raw {
-					target := &(*target)[i]
+					len(src))
+				for i, src := range src {
+					dst := &(*dst)[i]
 					err = __unmarshalInterfaceListOfListOfListsFieldListOfListsOfListsOfContent(
-						target, raw)
+						src, dst)
 					if err != nil {
 						return fmt.Errorf(
 							"Unable to unmarshal InterfaceListOfListOfListsFieldResponse.ListOfListsOfListsOfContent: %w", err)
@@ -193,26 +197,26 @@ func (v *InterfaceListOfListOfListsFieldResponse) UnmarshalJSON(b []byte) error
 	}
 
 	{
-		target := &v.WithPointer
-		raw := firstPass.WithPointer
-		*target = make(
+		dst := &v.WithPointer
+		src := firstPass.WithPointer
+		*dst = make(
 			[][][]*InterfaceListOfListOfListsFieldWithPointerContent,
-			len(raw))
-		for i, raw := range raw {
-			target := &(*target)[i]
-			*target = make(
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
+			*dst = make(
 				[][]*InterfaceListOfListOfListsFieldWithPointerContent,
-				len(raw))
-			for i, raw := range raw {
-				target := &(*target)[i]
-				*target = make(
+				len(src))
+			for i, src := range src {
+				dst := &(*dst)[i]
+				*dst = make(
 					[]*InterfaceListOfListOfListsFieldWithPointerContent,
-					len(raw))
-				for i, raw := range raw {
-					target := &(*target)[i]
-					*target = new(InterfaceListOfListOfListsFieldWithPointerContent)
+					len(src))
+				for i, src := range src {
+					dst := &(*dst)[i]
+					*dst = new(InterfaceListOfListOfListsFieldWithPointerContent)
 					err = __unmarshalInterfaceListOfListOfListsFieldWithPointerContent(
-						*target, raw)
+						src, *dst)
 					if err != nil {
 						return fmt.Errorf(
 							"Unable to unmarshal InterfaceListOfListOfListsFieldResponse.WithPointer: %w", err)
@@ -290,15 +294,15 @@ func (v *InterfaceListOfListOfListsFieldWithPointerTopic) GetId() *testutil.ID {
 // GetName is a part of, and documented with, the interface InterfaceListOfListOfListsFieldWithPointerContent.
 func (v *InterfaceListOfListOfListsFieldWithPointerTopic) GetName() *string { return v.Name }
 
-func __unmarshalInterfaceListOfListOfListsFieldWithPointerContent(v *InterfaceListOfListOfListsFieldWithPointerContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInterfaceListOfListOfListsFieldWithPointerContent(b []byte, v *InterfaceListOfListOfListsFieldWithPointerContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -306,13 +310,13 @@ func __unmarshalInterfaceListOfListOfListsFieldWithPointerContent(v *InterfaceLi
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InterfaceListOfListOfListsFieldWithPointerArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InterfaceListOfListOfListsFieldWithPointerVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(InterfaceListOfListOfListsFieldWithPointerTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")

generate/testdata/snapshots/TestGenerate-InterfaceNesting.graphql-InterfaceNesting.graphql.go

@@ -24,6 +24,10 @@ type InterfaceNestingRootTopic struct {
 
 func (v *InterfaceNestingRootTopic) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InterfaceNestingRootTopic
 		Children []json.RawMessage `json:"children"`
@@ -37,15 +41,15 @@ func (v *InterfaceNestingRootTopic) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.Children
-		raw := firstPass.Children
-		*target = make(
+		dst := &v.Children
+		src := firstPass.Children
+		*dst = make(
 			[]InterfaceNestingRootTopicChildrenContent,
-			len(raw))
-		for i, raw := range raw {
-			target := &(*target)[i]
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
 			err = __unmarshalInterfaceNestingRootTopicChildrenContent(
-				target, raw)
+				src, dst)
 			if err != nil {
 				return fmt.Errorf(
 					"Unable to unmarshal InterfaceNestingRootTopic.Children: %w", err)
@@ -127,15 +131,15 @@ func (v *InterfaceNestingRootTopicChildrenTopic) GetParent() InterfaceNestingRoo
 	return v.Parent
 }
 
-func __unmarshalInterfaceNestingRootTopicChildrenContent(v *InterfaceNestingRootTopicChildrenContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInterfaceNestingRootTopicChildrenContent(b []byte, v *InterfaceNestingRootTopicChildrenContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -143,13 +147,13 @@ func __unmarshalInterfaceNestingRootTopicChildrenContent(v *InterfaceNestingRoot
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InterfaceNestingRootTopicChildrenArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InterfaceNestingRootTopicChildrenVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(InterfaceNestingRootTopicChildrenTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -168,6 +172,10 @@ type InterfaceNestingRootTopicChildrenContentParentTopic struct {
 
 func (v *InterfaceNestingRootTopicChildrenContentParentTopic) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InterfaceNestingRootTopicChildrenContentParentTopic
 		Children []json.RawMessage `json:"children"`
@@ -181,15 +189,15 @@ func (v *InterfaceNestingRootTopicChildrenContentParentTopic) UnmarshalJSON(b []
 	}
 
 	{
-		target := &v.Children
-		raw := firstPass.Children
-		*target = make(
+		dst := &v.Children
+		src := firstPass.Children
+		*dst = make(
 			[]InterfaceNestingRootTopicChildrenContentParentTopicChildrenContent,
-			len(raw))
-		for i, raw := range raw {
-			target := &(*target)[i]
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
 			err = __unmarshalInterfaceNestingRootTopicChildrenContentParentTopicChildrenContent(
-				target, raw)
+				src, dst)
 			if err != nil {
 				return fmt.Errorf(
 					"Unable to unmarshal InterfaceNestingRootTopicChildrenContentParentTopic.Children: %w", err)
@@ -265,15 +273,15 @@ func (v *InterfaceNestingRootTopicChildrenContentParentTopicChildrenTopic) GetId
 	return v.Id
 }
 
-func __unmarshalInterfaceNestingRootTopicChildrenContentParentTopicChildrenContent(v *InterfaceNestingRootTopicChildrenContentParentTopicChildrenContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInterfaceNestingRootTopicChildrenContentParentTopicChildrenContent(b []byte, v *InterfaceNestingRootTopicChildrenContentParentTopicChildrenContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -281,13 +289,13 @@ func __unmarshalInterfaceNestingRootTopicChildrenContentParentTopicChildrenConte
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InterfaceNestingRootTopicChildrenContentParentTopicChildrenArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InterfaceNestingRootTopicChildrenContentParentTopicChildrenVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(InterfaceNestingRootTopicChildrenContentParentTopicChildrenTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")

generate/testdata/snapshots/TestGenerate-InterfaceNoFragments.graphql-InterfaceNoFragments.graphql.go

@@ -76,15 +76,15 @@ func (v *InterfaceNoFragmentsQueryRandomItemTopic) GetId() testutil.ID { return
 // GetName is a part of, and documented with, the interface InterfaceNoFragmentsQueryRandomItemContent.
 func (v *InterfaceNoFragmentsQueryRandomItemTopic) GetName() string { return v.Name }
 
-func __unmarshalInterfaceNoFragmentsQueryRandomItemContent(v *InterfaceNoFragmentsQueryRandomItemContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInterfaceNoFragmentsQueryRandomItemContent(b []byte, v *InterfaceNoFragmentsQueryRandomItemContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -92,13 +92,13 @@ func __unmarshalInterfaceNoFragmentsQueryRandomItemContent(v *InterfaceNoFragmen
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InterfaceNoFragmentsQueryRandomItemArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InterfaceNoFragmentsQueryRandomItemVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(InterfaceNoFragmentsQueryRandomItemTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -196,15 +196,15 @@ func (v *InterfaceNoFragmentsQueryRandomItemWithTypeNameTopic) GetId() testutil.
 // GetName is a part of, and documented with, the interface InterfaceNoFragmentsQueryRandomItemWithTypeNameContent.
 func (v *InterfaceNoFragmentsQueryRandomItemWithTypeNameTopic) GetName() string { return v.Name }
 
-func __unmarshalInterfaceNoFragmentsQueryRandomItemWithTypeNameContent(v *InterfaceNoFragmentsQueryRandomItemWithTypeNameContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInterfaceNoFragmentsQueryRandomItemWithTypeNameContent(b []byte, v *InterfaceNoFragmentsQueryRandomItemWithTypeNameContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -212,13 +212,13 @@ func __unmarshalInterfaceNoFragmentsQueryRandomItemWithTypeNameContent(v *Interf
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InterfaceNoFragmentsQueryRandomItemWithTypeNameArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InterfaceNoFragmentsQueryRandomItemWithTypeNameVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(InterfaceNoFragmentsQueryRandomItemWithTypeNameTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -254,6 +254,10 @@ type InterfaceNoFragmentsQueryResponse struct {
 
 func (v *InterfaceNoFragmentsQueryResponse) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*InterfaceNoFragmentsQueryResponse
 		RandomItem             json.RawMessage `json:"randomItem"`
@@ -269,10 +273,10 @@ func (v *InterfaceNoFragmentsQueryResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RandomItem
-		raw := firstPass.RandomItem
+		dst := &v.RandomItem
+		src := firstPass.RandomItem
 		err = __unmarshalInterfaceNoFragmentsQueryRandomItemContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal InterfaceNoFragmentsQueryResponse.RandomItem: %w", err)
@@ -280,10 +284,10 @@ func (v *InterfaceNoFragmentsQueryResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RandomItemWithTypeName
-		raw := firstPass.RandomItemWithTypeName
+		dst := &v.RandomItemWithTypeName
+		src := firstPass.RandomItemWithTypeName
 		err = __unmarshalInterfaceNoFragmentsQueryRandomItemWithTypeNameContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal InterfaceNoFragmentsQueryResponse.RandomItemWithTypeName: %w", err)
@@ -291,11 +295,11 @@ func (v *InterfaceNoFragmentsQueryResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.WithPointer
-		raw := firstPass.WithPointer
-		*target = new(InterfaceNoFragmentsQueryWithPointerContent)
+		dst := &v.WithPointer
+		src := firstPass.WithPointer
+		*dst = new(InterfaceNoFragmentsQueryWithPointerContent)
 		err = __unmarshalInterfaceNoFragmentsQueryWithPointerContent(
-			*target, raw)
+			src, *dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal InterfaceNoFragmentsQueryResponse.WithPointer: %w", err)
@@ -377,15 +381,15 @@ func (v *InterfaceNoFragmentsQueryWithPointerTopic) GetId() *testutil.ID { retur
 // GetName is a part of, and documented with, the interface InterfaceNoFragmentsQueryWithPointerContent.
 func (v *InterfaceNoFragmentsQueryWithPointerTopic) GetName() *string { return v.Name }
 
-func __unmarshalInterfaceNoFragmentsQueryWithPointerContent(v *InterfaceNoFragmentsQueryWithPointerContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalInterfaceNoFragmentsQueryWithPointerContent(b []byte, v *InterfaceNoFragmentsQueryWithPointerContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -393,13 +397,13 @@ func __unmarshalInterfaceNoFragmentsQueryWithPointerContent(v *InterfaceNoFragme
 	switch tn.TypeName {
 	case "Article":
 		*v = new(InterfaceNoFragmentsQueryWithPointerArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(InterfaceNoFragmentsQueryWithPointerVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(InterfaceNoFragmentsQueryWithPointerTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")

generate/testdata/snapshots/TestGenerate-Omitempty.graphql-Omitempty.graphql.go

@@ -3,6 +3,8 @@ package test
 // Code generated by github.com/Khan/genqlient, DO NOT EDIT.
 
 import (
+	"encoding/json"
+	"fmt"
 	"time"
 
 	"github.com/Khan/genqlient/graphql"
@@ -70,6 +72,32 @@ type UserQueryInput struct {
 	Role       Role             `json:"role"`
 	Names      []string         `json:"names"`
 	HasPokemon testutil.Pokemon `json:"hasPokemon"`
+	Birthdate  time.Time        `json:"-"`
+}
+
+func (v *UserQueryInput) MarshalJSON() ([]byte, error) {
+
+	var fullObject struct {
+		*UserQueryInput
+		Birthdate json.RawMessage `json:"birthdate"`
+		graphql.NoMarshalJSON
+	}
+	fullObject.UserQueryInput = v
+
+	{
+
+		dst := &fullObject.Birthdate
+		src := v.Birthdate
+		var err error
+		*dst, err = testutil.MarshalDate(
+			&src)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"Unable to marshal UserQueryInput.Birthdate: %w", err)
+		}
+	}
+
+	return json.Marshal(&fullObject)
 }
 
 // __OmitEmptyQueryInput is used internally by genqlient

generate/testdata/snapshots/TestGenerate-Pointers.graphql-Pointers.graphql.go

@@ -3,6 +3,8 @@ package test
 // Code generated by github.com/Khan/genqlient, DO NOT EDIT.
 
 import (
+	"encoding/json"
+	"fmt"
 	"time"
 
 	"github.com/Khan/genqlient/graphql"
@@ -77,6 +79,32 @@ type UserQueryInput struct {
 	Role       *Role             `json:"role"`
 	Names      []*string         `json:"names"`
 	HasPokemon *testutil.Pokemon `json:"hasPokemon"`
+	Birthdate  *time.Time        `json:"-"`
+}
+
+func (v *UserQueryInput) MarshalJSON() ([]byte, error) {
+
+	var fullObject struct {
+		*UserQueryInput
+		Birthdate json.RawMessage `json:"birthdate"`
+		graphql.NoMarshalJSON
+	}
+	fullObject.UserQueryInput = v
+
+	{
+
+		dst := &fullObject.Birthdate
+		src := v.Birthdate
+		var err error
+		*dst, err = testutil.MarshalDate(
+			src)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"Unable to marshal UserQueryInput.Birthdate: %w", err)
+		}
+	}
+
+	return json.Marshal(&fullObject)
 }
 
 // __PointersQueryInput is used internally by genqlient

generate/testdata/snapshots/TestGenerate-PointersInline.graphql-PointersInline.graphql.go

@@ -3,6 +3,8 @@ package test
 // Code generated by github.com/Khan/genqlient, DO NOT EDIT.
 
 import (
+	"encoding/json"
+	"fmt"
 	"time"
 
 	"github.com/Khan/genqlient/graphql"
@@ -77,6 +79,32 @@ type UserQueryInput struct {
 	Role       Role             `json:"role"`
 	Names      []string         `json:"names"`
 	HasPokemon testutil.Pokemon `json:"hasPokemon"`
+	Birthdate  time.Time        `json:"-"`
+}
+
+func (v *UserQueryInput) MarshalJSON() ([]byte, error) {
+
+	var fullObject struct {
+		*UserQueryInput
+		Birthdate json.RawMessage `json:"birthdate"`
+		graphql.NoMarshalJSON
+	}
+	fullObject.UserQueryInput = v
+
+	{
+
+		dst := &fullObject.Birthdate
+		src := v.Birthdate
+		var err error
+		*dst, err = testutil.MarshalDate(
+			&src)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"Unable to marshal UserQueryInput.Birthdate: %w", err)
+		}
+	}
+
+	return json.Marshal(&fullObject)
 }
 
 // __PointersQueryInput is used internally by genqlient

generate/testdata/snapshots/TestGenerate-SimpleInlineFragment.graphql-SimpleInlineFragment.graphql.go

@@ -77,15 +77,15 @@ func (v *SimpleInlineFragmentRandomItemTopic) GetId() testutil.ID { return v.Id
 // GetName is a part of, and documented with, the interface SimpleInlineFragmentRandomItemContent.
 func (v *SimpleInlineFragmentRandomItemTopic) GetName() string { return v.Name }
 
-func __unmarshalSimpleInlineFragmentRandomItemContent(v *SimpleInlineFragmentRandomItemContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalSimpleInlineFragmentRandomItemContent(b []byte, v *SimpleInlineFragmentRandomItemContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -93,13 +93,13 @@ func __unmarshalSimpleInlineFragmentRandomItemContent(v *SimpleInlineFragmentRan
 	switch tn.TypeName {
 	case "Article":
 		*v = new(SimpleInlineFragmentRandomItemArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(SimpleInlineFragmentRandomItemVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(SimpleInlineFragmentRandomItemTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -133,6 +133,10 @@ type SimpleInlineFragmentResponse struct {
 
 func (v *SimpleInlineFragmentResponse) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*SimpleInlineFragmentResponse
 		RandomItem json.RawMessage `json:"randomItem"`
@@ -146,10 +150,10 @@ func (v *SimpleInlineFragmentResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RandomItem
-		raw := firstPass.RandomItem
+		dst := &v.RandomItem
+		src := firstPass.RandomItem
 		err = __unmarshalSimpleInlineFragmentRandomItemContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal SimpleInlineFragmentResponse.RandomItem: %w", err)

generate/testdata/snapshots/TestGenerate-SimpleNamedFragment.graphql-SimpleNamedFragment.graphql.go

@@ -76,15 +76,15 @@ func (v *SimpleNamedFragmentRandomItemTopic) GetId() testutil.ID { return v.Id }
 // GetName is a part of, and documented with, the interface SimpleNamedFragmentRandomItemContent.
 func (v *SimpleNamedFragmentRandomItemTopic) GetName() string { return v.Name }
 
-func __unmarshalSimpleNamedFragmentRandomItemContent(v *SimpleNamedFragmentRandomItemContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalSimpleNamedFragmentRandomItemContent(b []byte, v *SimpleNamedFragmentRandomItemContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -92,13 +92,13 @@ func __unmarshalSimpleNamedFragmentRandomItemContent(v *SimpleNamedFragmentRando
 	switch tn.TypeName {
 	case "Article":
 		*v = new(SimpleNamedFragmentRandomItemArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(SimpleNamedFragmentRandomItemVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(SimpleNamedFragmentRandomItemTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -127,6 +127,10 @@ type SimpleNamedFragmentRandomItemVideo struct {
 
 func (v *SimpleNamedFragmentRandomItemVideo) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*SimpleNamedFragmentRandomItemVideo
 		graphql.NoUnmarshalJSON
@@ -177,15 +181,15 @@ func (v *SimpleNamedFragmentRandomLeafVideo) implementsGraphQLInterfaceSimpleNam
 // GetTypename is a part of, and documented with, the interface SimpleNamedFragmentRandomLeafLeafContent.
 func (v *SimpleNamedFragmentRandomLeafVideo) GetTypename() string { return v.Typename }
 
-func __unmarshalSimpleNamedFragmentRandomLeafLeafContent(v *SimpleNamedFragmentRandomLeafLeafContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalSimpleNamedFragmentRandomLeafLeafContent(b []byte, v *SimpleNamedFragmentRandomLeafLeafContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -193,10 +197,10 @@ func __unmarshalSimpleNamedFragmentRandomLeafLeafContent(v *SimpleNamedFragmentR
 	switch tn.TypeName {
 	case "Article":
 		*v = new(SimpleNamedFragmentRandomLeafArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(SimpleNamedFragmentRandomLeafVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing LeafContent.__typename")
@@ -214,6 +218,10 @@ type SimpleNamedFragmentRandomLeafVideo struct {
 
 func (v *SimpleNamedFragmentRandomLeafVideo) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*SimpleNamedFragmentRandomLeafVideo
 		graphql.NoUnmarshalJSON
@@ -241,6 +249,10 @@ type SimpleNamedFragmentResponse struct {
 
 func (v *SimpleNamedFragmentResponse) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*SimpleNamedFragmentResponse
 		RandomItem json.RawMessage `json:"randomItem"`
@@ -255,10 +267,10 @@ func (v *SimpleNamedFragmentResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RandomItem
-		raw := firstPass.RandomItem
+		dst := &v.RandomItem
+		src := firstPass.RandomItem
 		err = __unmarshalSimpleNamedFragmentRandomItemContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal SimpleNamedFragmentResponse.RandomItem: %w", err)
@@ -266,10 +278,10 @@ func (v *SimpleNamedFragmentResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RandomLeaf
-		raw := firstPass.RandomLeaf
+		dst := &v.RandomLeaf
+		src := firstPass.RandomLeaf
 		err = __unmarshalSimpleNamedFragmentRandomLeafLeafContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal SimpleNamedFragmentResponse.RandomLeaf: %w", err)

generate/testdata/snapshots/TestGenerate-StructOption.graphql-StructOption.graphql.go

@@ -62,6 +62,10 @@ type StructOptionRootTopicChildrenContentParentTopic struct {
 
 func (v *StructOptionRootTopicChildrenContentParentTopic) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*StructOptionRootTopicChildrenContentParentTopic
 		InterfaceChildren []json.RawMessage `json:"interfaceChildren"`
@@ -75,15 +79,15 @@ func (v *StructOptionRootTopicChildrenContentParentTopic) UnmarshalJSON(b []byte
 	}
 
 	{
-		target := &v.InterfaceChildren
-		raw := firstPass.InterfaceChildren
-		*target = make(
+		dst := &v.InterfaceChildren
+		src := firstPass.InterfaceChildren
+		*dst = make(
 			[]StructOptionRootTopicChildrenContentParentTopicInterfaceChildrenContent,
-			len(raw))
-		for i, raw := range raw {
-			target := &(*target)[i]
+			len(src))
+		for i, src := range src {
+			dst := &(*dst)[i]
 			err = __unmarshalStructOptionRootTopicChildrenContentParentTopicInterfaceChildrenContent(
-				target, raw)
+				src, dst)
 			if err != nil {
 				return fmt.Errorf(
 					"Unable to unmarshal StructOptionRootTopicChildrenContentParentTopic.InterfaceChildren: %w", err)
@@ -169,15 +173,15 @@ func (v *StructOptionRootTopicChildrenContentParentTopicInterfaceChildrenTopic)
 	return v.Id
 }
 
-func __unmarshalStructOptionRootTopicChildrenContentParentTopicInterfaceChildrenContent(v *StructOptionRootTopicChildrenContentParentTopicInterfaceChildrenContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalStructOptionRootTopicChildrenContentParentTopicInterfaceChildrenContent(b []byte, v *StructOptionRootTopicChildrenContentParentTopicInterfaceChildrenContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -185,13 +189,13 @@ func __unmarshalStructOptionRootTopicChildrenContentParentTopicInterfaceChildren
 	switch tn.TypeName {
 	case "Article":
 		*v = new(StructOptionRootTopicChildrenContentParentTopicInterfaceChildrenArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(StructOptionRootTopicChildrenContentParentTopicInterfaceChildrenVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(StructOptionRootTopicChildrenContentParentTopicInterfaceChildrenTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -218,6 +222,10 @@ type StructOptionRootTopicChildrenContentParentTopicInterfaceChildrenVideo struc
 
 func (v *StructOptionRootTopicChildrenContentParentTopicInterfaceChildrenVideo) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*StructOptionRootTopicChildrenContentParentTopicInterfaceChildrenVideo
 		graphql.NoUnmarshalJSON

generate/testdata/snapshots/TestGenerate-TypeNames.graphql-TypeNames.graphql.go

@@ -65,15 +65,15 @@ func (v *ItemTopic) GetId() testutil.ID { return v.Id }
 // GetName is a part of, and documented with, the interface Item.
 func (v *ItemTopic) GetName() string { return v.Name }
 
-func __unmarshalItem(v *Item, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalItem(b []byte, v *Item) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -81,13 +81,13 @@ func __unmarshalItem(v *Item, m json.RawMessage) error {
 	switch tn.TypeName {
 	case "Article":
 		*v = new(ItemArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(ItemVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Topic":
 		*v = new(ItemTopic)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing Content.__typename")
@@ -134,6 +134,10 @@ type Resp struct {
 
 func (v *Resp) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*Resp
 		RandomItem json.RawMessage `json:"randomItem"`
@@ -147,10 +151,10 @@ func (v *Resp) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RandomItem
-		raw := firstPass.RandomItem
+		dst := &v.RandomItem
+		src := firstPass.RandomItem
 		err = __unmarshalItem(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal Resp.RandomItem: %w", err)

generate/testdata/snapshots/TestGenerate-UnionNoFragments.graphql-UnionNoFragments.graphql.go

@@ -40,15 +40,15 @@ func (v *UnionNoFragmentsQueryRandomLeafVideo) implementsGraphQLInterfaceUnionNo
 // GetTypename is a part of, and documented with, the interface UnionNoFragmentsQueryRandomLeafLeafContent.
 func (v *UnionNoFragmentsQueryRandomLeafVideo) GetTypename() string { return v.Typename }
 
-func __unmarshalUnionNoFragmentsQueryRandomLeafLeafContent(v *UnionNoFragmentsQueryRandomLeafLeafContent, m json.RawMessage) error {
-	if string(m) == "null" {
+func __unmarshalUnionNoFragmentsQueryRandomLeafLeafContent(b []byte, v *UnionNoFragmentsQueryRandomLeafLeafContent) error {
+	if string(b) == "null" {
 		return nil
 	}
 
 	var tn struct {
 		TypeName string `json:"__typename"`
 	}
-	err := json.Unmarshal(m, &tn)
+	err := json.Unmarshal(b, &tn)
 	if err != nil {
 		return err
 	}
@@ -56,10 +56,10 @@ func __unmarshalUnionNoFragmentsQueryRandomLeafLeafContent(v *UnionNoFragmentsQu
 	switch tn.TypeName {
 	case "Article":
 		*v = new(UnionNoFragmentsQueryRandomLeafArticle)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "Video":
 		*v = new(UnionNoFragmentsQueryRandomLeafVideo)
-		return json.Unmarshal(m, *v)
+		return json.Unmarshal(b, *v)
 	case "":
 		return fmt.Errorf(
 			"Response was missing LeafContent.__typename")
@@ -81,6 +81,10 @@ type UnionNoFragmentsQueryResponse struct {
 
 func (v *UnionNoFragmentsQueryResponse) UnmarshalJSON(b []byte) error {
 
+	if string(b) == "null" {
+		return nil
+	}
+
 	var firstPass struct {
 		*UnionNoFragmentsQueryResponse
 		RandomLeaf json.RawMessage `json:"randomLeaf"`
@@ -94,10 +98,10 @@ func (v *UnionNoFragmentsQueryResponse) UnmarshalJSON(b []byte) error {
 	}
 
 	{
-		target := &v.RandomLeaf
-		raw := firstPass.RandomLeaf
+		dst := &v.RandomLeaf
+		src := firstPass.RandomLeaf
 		err = __unmarshalUnionNoFragmentsQueryRandomLeafLeafContent(
-			target, raw)
+			src, dst)
 		if err != nil {
 			return fmt.Errorf(
 				"Unable to unmarshal UnionNoFragmentsQueryResponse.RandomLeaf: %w", err)

generate/testdata/snapshots/TestGenerate-unexported.graphql-unexported.graphql.go

@@ -3,6 +3,10 @@ package test
 // Code generated by github.com/Khan/genqlient, DO NOT EDIT.
 
 import (
+	"encoding/json"
+	"fmt"
+	"time"
+
 	"github.com/Khan/genqlient/graphql"
 	"github.com/Khan/genqlient/internal/testutil"
 )
@@ -34,6 +38,32 @@ type UserQueryInput struct {
 	Role       Role             `json:"role"`
 	Names      []string         `json:"names"`
 	HasPokemon testutil.Pokemon `json:"hasPokemon"`
+	Birthdate  time.Time        `json:"-"`
+}
+
+func (v *UserQueryInput) MarshalJSON() ([]byte, error) {
+
+	var fullObject struct {
+		*UserQueryInput
+		Birthdate json.RawMessage `json:"birthdate"`
+		graphql.NoMarshalJSON
+	}
+	fullObject.UserQueryInput = v
+
+	{
+
+		dst := &fullObject.Birthdate
+		src := v.Birthdate
+		var err error
+		*dst, err = testutil.MarshalDate(
+			&src)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"Unable to marshal UserQueryInput.Birthdate: %w", err)
+		}
+	}
+
+	return json.Marshal(&fullObject)
 }
 
 // __unexportedInput is used internally by genqlient