fix: premarshal structs get generated with omitempty tag (#267)

This PR addresses a bug described in #263

Basically, whenever a struct involves a custom genqlient binding, a
secondary "premarshal" struct gets generated.

The bug was that this "premarshal" struct was not propagating the
`omitempty` JSON tags, which was resulting in unexpected behavior.

The fix involved a few changed lines in the Go template, and a few
changes in the unit tests.

I have:
- [x] Written a clear PR title and description (above)
- [x] Signed the [Khan Academy CLA](https://www.khanacademy.org/r/cla)
- [x] Added tests covering my changes, if applicable
- [x] Included a link to the issue fixed, if applicable
- [x] Included documentation, for new features (n/a)
- [x] Added an entry to the changelog

docs/CHANGELOG.md

@@ -34,6 +34,7 @@ When releasing a new version:
 - Fixed non-deterministic generated code when querying graphql interfaces.
 - Fixed generated code when last component of package name is not a valid identifier (e.g. `"path/to/my-package"`).
 - Fixed incorrect documentation of `for` directive.
+- Fixed bug where `omitempty` JSON tags were not being correctly applied to `__premarshal` structs.
 
 ## v0.5.0
 

generate/marshal.go.tmpl

@@ -31,9 +31,9 @@
 type __premarshal{{.GoName}} struct{
     {{range .FlattenedFields -}}
     {{if .NeedsMarshaling -}}
-    {{.GoName}} {{repeat .GoType.SliceDepth "[]"}}{{ref "encoding/json.RawMessage"}} `json:"{{.JSONName}}"`
+    {{.GoName}} {{repeat .GoType.SliceDepth "[]"}}{{ref "encoding/json.RawMessage"}} `json:"{{.JSONName}}{{if .Omitempty -}},omitempty{{end}}"`
     {{else}}
-    {{.GoName}} {{.GoType.Reference}} `json:"{{.JSONName}}"`
+    {{.GoName}} {{.GoType.Reference}} `json:"{{.JSONName}}{{if .Omitempty -}},omitempty{{end}}"`
     {{end}}
     {{end}}
 }

generate/testdata/queries/Hasura.graphql

@@ -0,0 +1,7 @@
+# @genqlient(pointer: true)
+query GetPokemon($where: getPokemonBoolExp!) {
+  getPokemon(where: $where) {
+    species
+    level
+  }
+}

generate/testdata/queries/schema.graphql

@@ -180,8 +180,28 @@ type Query {
   listOfListsOfListsOfContent: [[[Content!]!]!]!
   recur(input: RecursiveInput!): Recursive
   acceptsListOfListOfListsOfDates(datesss: [[[Date!]!]!]!): Boolean
+  getPokemon(where: getPokemonBoolExp): [Pokemon!]!
 }
 
 type Mutation {
   createUser(name: String!, email: String): User 
 }
+
+input getPokemonBoolExp {
+  _and: [getPokemonBoolExp!]
+  _not: getPokemonBoolExp
+  _or: [getPokemonBoolExp!]
+  level: IntComparisonExp
+}
+
+input IntComparisonExp {
+  _eq: Int
+  _gt: Int
+  _gte: Int
+  _in: [Int!]
+  _isNull: Boolean
+  _lt: Int
+  _lte: Int
+  _neq: Int
+  _nin: [Int!]
+}

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

@@ -0,0 +1,118 @@
+// Code generated by github.com/Khan/genqlient, DO NOT EDIT.
+
+package test
+
+import (
+	"github.com/Khan/genqlient/graphql"
+	"github.com/Khan/genqlient/internal/testutil"
+)
+
+type GetPokemonBoolExp struct {
+	And   []*GetPokemonBoolExp `json:"_and"`
+	Not   *GetPokemonBoolExp   `json:"_not"`
+	Or    []*GetPokemonBoolExp `json:"_or"`
+	Level *IntComparisonExp    `json:"level"`
+}
+
+// GetAnd returns GetPokemonBoolExp.And, and is useful for accessing the field via an interface.
+func (v *GetPokemonBoolExp) GetAnd() []*GetPokemonBoolExp { return v.And }
+
+// GetNot returns GetPokemonBoolExp.Not, and is useful for accessing the field via an interface.
+func (v *GetPokemonBoolExp) GetNot() *GetPokemonBoolExp { return v.Not }
+
+// GetOr returns GetPokemonBoolExp.Or, and is useful for accessing the field via an interface.
+func (v *GetPokemonBoolExp) GetOr() []*GetPokemonBoolExp { return v.Or }
+
+// GetLevel returns GetPokemonBoolExp.Level, and is useful for accessing the field via an interface.
+func (v *GetPokemonBoolExp) GetLevel() *IntComparisonExp { return v.Level }
+
+// GetPokemonResponse is returned by GetPokemon on success.
+type GetPokemonResponse struct {
+	GetPokemon []*testutil.Pokemon `json:"getPokemon"`
+}
+
+// GetGetPokemon returns GetPokemonResponse.GetPokemon, and is useful for accessing the field via an interface.
+func (v *GetPokemonResponse) GetGetPokemon() []*testutil.Pokemon { return v.GetPokemon }
+
+type IntComparisonExp struct {
+	Eq     *int   `json:"_eq"`
+	Gt     *int   `json:"_gt"`
+	Gte    *int   `json:"_gte"`
+	In     []*int `json:"_in"`
+	IsNull *bool  `json:"_isNull"`
+	Lt     *int   `json:"_lt"`
+	Lte    *int   `json:"_lte"`
+	Neq    *int   `json:"_neq"`
+	Nin    []*int `json:"_nin"`
+}
+
+// GetEq returns IntComparisonExp.Eq, and is useful for accessing the field via an interface.
+func (v *IntComparisonExp) GetEq() *int { return v.Eq }
+
+// GetGt returns IntComparisonExp.Gt, and is useful for accessing the field via an interface.
+func (v *IntComparisonExp) GetGt() *int { return v.Gt }
+
+// GetGte returns IntComparisonExp.Gte, and is useful for accessing the field via an interface.
+func (v *IntComparisonExp) GetGte() *int { return v.Gte }
+
+// GetIn returns IntComparisonExp.In, and is useful for accessing the field via an interface.
+func (v *IntComparisonExp) GetIn() []*int { return v.In }
+
+// GetIsNull returns IntComparisonExp.IsNull, and is useful for accessing the field via an interface.
+func (v *IntComparisonExp) GetIsNull() *bool { return v.IsNull }
+
+// GetLt returns IntComparisonExp.Lt, and is useful for accessing the field via an interface.
+func (v *IntComparisonExp) GetLt() *int { return v.Lt }
+
+// GetLte returns IntComparisonExp.Lte, and is useful for accessing the field via an interface.
+func (v *IntComparisonExp) GetLte() *int { return v.Lte }
+
+// GetNeq returns IntComparisonExp.Neq, and is useful for accessing the field via an interface.
+func (v *IntComparisonExp) GetNeq() *int { return v.Neq }
+
+// GetNin returns IntComparisonExp.Nin, and is useful for accessing the field via an interface.
+func (v *IntComparisonExp) GetNin() []*int { return v.Nin }
+
+// __GetPokemonInput is used internally by genqlient
+type __GetPokemonInput struct {
+	Where *GetPokemonBoolExp `json:"where"`
+}
+
+// GetWhere returns __GetPokemonInput.Where, and is useful for accessing the field via an interface.
+func (v *__GetPokemonInput) GetWhere() *GetPokemonBoolExp { return v.Where }
+
+// The query or mutation executed by GetPokemon.
+const GetPokemon_Operation = `
+query GetPokemon ($where: getPokemonBoolExp!) {
+	getPokemon(where: $where) {
+		species
+		level
+	}
+}
+`
+
+func GetPokemon(
+	client graphql.Client,
+	where *GetPokemonBoolExp,
+) (*GetPokemonResponse, error) {
+	req := &graphql.Request{
+		OpName: "GetPokemon",
+		Query:  GetPokemon_Operation,
+		Variables: &__GetPokemonInput{
+			Where: where,
+		},
+	}
+	var err error
+
+	var data GetPokemonResponse
+	resp := &graphql.Response{Data: &data}
+
+	err = client.MakeRequest(
+		nil,
+		req,
+		resp,
+	)
+
+	return &data, err
+}
+

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

@@ -0,0 +1,9 @@
+{
+  "operations": [
+    {
+      "operationName": "GetPokemon",
+      "query": "\nquery GetPokemon ($where: getPokemonBoolExp!) {\n\tgetPokemon(where: $where) {\n\t\tspecies\n\t\tlevel\n\t}\n}\n",
+      "sourceLocation": "testdata/queries/Hasura.graphql"
+    }
+  ]
+}

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

@@ -83,19 +83,19 @@ func (v *MyInput) UnmarshalJSON(b []byte) error {
 }
 
 type __premarshalMyInput struct {
-	Email *string `json:"email"`
+	Email *string `json:"email,omitempty"`
 
-	Name *string `json:"name"`
+	Name *string `json:"name,omitempty"`
 
-	Id *testutil.ID `json:"id"`
+	Id *testutil.ID `json:"id,omitempty"`
 
-	Role *Role `json:"role"`
+	Role *Role `json:"role,omitempty"`
 
-	Names []*string `json:"names"`
+	Names []*string `json:"names,omitempty"`
 
-	HasPokemon *testutil.Pokemon `json:"hasPokemon"`
+	HasPokemon *testutil.Pokemon `json:"hasPokemon,omitempty"`
 
-	Birthdate json.RawMessage `json:"birthdate"`
+	Birthdate json.RawMessage `json:"birthdate,omitempty"`
 }
 
 func (v *MyInput) MarshalJSON() ([]byte, error) {
@@ -264,19 +264,19 @@ func (v *UserQueryInput) UnmarshalJSON(b []byte) error {
 }
 
 type __premarshalUserQueryInput struct {
-	Email *string `json:"email"`
+	Email *string `json:"email,omitempty"`
 
-	Name *string `json:"name"`
+	Name *string `json:"name,omitempty"`
 
-	Id *testutil.ID `json:"id"`
+	Id *testutil.ID `json:"id,omitempty"`
 
-	Role *Role `json:"role"`
+	Role *Role `json:"role,omitempty"`
 
-	Names []*string `json:"names"`
+	Names []*string `json:"names,omitempty"`
 
-	HasPokemon *testutil.Pokemon `json:"hasPokemon"`
+	HasPokemon *testutil.Pokemon `json:"hasPokemon,omitempty"`
 
-	Birthdate json.RawMessage `json:"birthdate"`
+	Birthdate json.RawMessage `json:"birthdate,omitempty"`
 }
 
 func (v *UserQueryInput) MarshalJSON() ([]byte, error) {

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

@@ -148,19 +148,19 @@ func (v *UserQueryInput) UnmarshalJSON(b []byte) error {
 }
 
 type __premarshalUserQueryInput struct {
-	Email string `json:"email"`
+	Email string `json:"email,omitempty"`
 
-	Name string `json:"name"`
+	Name string `json:"name,omitempty"`
 
 	Id testutil.ID `json:"id"`
 
-	Role Role `json:"role"`
+	Role Role `json:"role,omitempty"`
 
-	Names []string `json:"names"`
+	Names []string `json:"names,omitempty"`
 
-	HasPokemon testutil.Pokemon `json:"hasPokemon"`
+	HasPokemon testutil.Pokemon `json:"hasPokemon,omitempty"`
 
-	Birthdate json.RawMessage `json:"birthdate"`
+	Birthdate json.RawMessage `json:"birthdate,omitempty"`
 }
 
 func (v *UserQueryInput) MarshalJSON() ([]byte, error) {