total rewrite to interface handling; not complete but it compiles

README.md

@@ -51,7 +51,7 @@ For a complete working example, see `example/`.
 
 ## Tests
 
-`go test ./...` does some perfunctory tests.  (This is run by GitHub Actions.)
+`go test ./...` tests code generation.  (This is run by GitHub Actions.)
 
 `make example` tests that everything wires up to a real API correctly.
 
@@ -69,6 +69,7 @@ Config options:
 - proper config/arguments setup (e.g. with [viper](https://github.com/spf13/viper)
 
 Other:
+- naming collisions are a mess
 - error-checking/validation/etc. everywhere
 - more tests
 - documentation

example/generated.go

@@ -8,16 +8,20 @@ import (
 	"github.com/Khan/genql/graphql"
 )
 
+type User struct {
+	MyName *string
+}
+
+type User1 struct {
+	TheirName *string `json:"theirName"`
+}
+
 type getUserResponse struct {
-	User *struct {
-		TheirName *string `json:"theirName"`
-	} `json:"user"`
+	User *User1 `json:"user"`
 }
 
 type getViewerResponse struct {
-	Viewer struct {
-		MyName *string
-	} `json:"viewer"`
+	Viewer User `json:"viewer"`
 }
 
 func getViewer(ctx context.Context, client *graphql.Client) (*getViewerResponse, error) {

generate/generate.go

@@ -4,22 +4,14 @@ import (
 	"bytes"
 	"fmt"
 	"go/format"
-	"path/filepath"
-	"runtime"
 	"sort"
 	"strings"
-	"text/template"
 
 	"github.com/vektah/gqlparser/ast"
 	"github.com/vektah/gqlparser/formatter"
 )
 
-// TODO: package template into the binary using one of those asset thingies
-var _, thisFilename, _, _ = runtime.Caller(0)
-var tmplRelFilename = "operation.go.tmpl"
-var tmplAbsFilename = filepath.Join(filepath.Dir(thisFilename), tmplRelFilename)
-
-var tmpl = template.Must(template.ParseFiles(tmplAbsFilename))
+var fileTemplate = mustTemplate("operation.go.tmpl")
 
 // generator is the context for the codegen process (and ends up getting passed
 // to the template).
@@ -29,8 +21,9 @@ type generator struct {
 	// The list of operations for which to generate code.
 	Operations []operation
 	// The types needed for these operations.
-	typeMap map[string]string
-	schema  *ast.Schema
+	typeMap    map[string]string
+	ImportJSON bool
+	schema     *ast.Schema
 }
 
 type operation struct {
@@ -165,7 +158,7 @@ func Generate(config *Config) ([]byte, error) {
 	}
 
 	var buf bytes.Buffer
-	err = tmpl.Execute(&buf, g)
+	err = fileTemplate.Execute(&buf, g)
 	if err != nil {
 		return nil, fmt.Errorf("could not render template: %v", err)
 	}

generate/operation.go.tmpl

@@ -1,9 +1,12 @@
-package {{$.Config.Package}}
+package {{.Config.Package}}
 
 // Code generated by github.com/Khan/genql, DO NOT EDIT.
 
 import (
 	"context"
+    {{- if .ImportJSON -}}
+    "encoding/json"
+    {{end}}
 
     "github.com/Khan/genql/graphql"
 )

generate/template.go

@@ -0,0 +1,15 @@
+package generate
+
+import (
+	"path/filepath"
+	"runtime"
+	"text/template"
+)
+
+// TODO: package templates into the binary using one of those asset thingies
+var _, thisFilename, _, _ = runtime.Caller(0)
+var thisDir = filepath.Dir(thisFilename)
+
+func mustTemplate(relFilename string) *template.Template {
+	return template.Must(template.ParseFiles(filepath.Join(thisDir, relFilename)))
+}

generate/testdata/InterfaceNoFragments.graphql

@@ -0,0 +1,10 @@
+query InterfaceNoFragmentsQuery {
+  root {
+    id
+    name
+    children {
+      id
+      name
+    }
+  }
+}

generate/testdata/InterfaceNoFragments.graphql.go

@@ -0,0 +1,97 @@
+package test
+
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type Article struct {
+	Id   string `json:"id"`
+	Name string `json:"name"`
+}
+
+func (v Article) implementsGraphQLInterfaceContent() {}
+
+type Content interface {
+	implementsGraphQLInterfaceContent()
+}
+
+type InterfaceNoFragmentsQueryResponse struct {
+	Root Topic `json:"root"`
+}
+
+type Topic struct {
+	Id       string    `json:"id"`
+	Name     string    `json:"name"`
+	Children []Content `json:"-"`
+}
+
+func (v *Topic) UnmarshalJSON(b []byte) error {
+	var firstPass struct {
+		*Topic
+		Children json.RawMessage `json:"children"`
+	}
+	firstPass.Topic = v
+
+	err := json.Unmarshal(b, &typenames)
+	if err != nil {
+		return err
+	}
+
+	var tn struct {
+		TypeName string `json:"__typename"`
+	}
+	err = json.Unmarshal(firstPass.Children, &tn)
+	if err != nil {
+		return err
+	}
+	switch tn.TypeName {
+
+	case "Article":
+		v.Children = Article{}
+		err = json.Unmarshal(
+			firstPass.Children, &v.Children)
+
+	case "Video":
+		v.Children = Video{}
+		err = json.Unmarshal(
+			firstPass.Children, &v.Children)
+
+	case "Topic":
+		v.Children = Topic{}
+		err = json.Unmarshal(
+			firstPass.Children, &v.Children)
+
+	}
+	if err != nil {
+		return err
+	}
+
+}
+
+type Video struct {
+	Id   string `json:"id"`
+	Name string `json:"name"`
+}
+
+func (v Video) implementsGraphQLInterfaceContent() {}
+
+func InterfaceNoFragmentsQuery(client *graphql.Client) (*InterfaceNoFragmentsQueryResponse, error) {
+	var retval InterfaceNoFragmentsQueryResponse
+	err := client.MakeRequest(context.Background(), `
+query InterfaceNoFragmentsQuery {
+	root {
+		id
+		name
+		children {
+			id
+			name
+		}
+	}
+}
+`, &retval, nil)
+	return &retval, err
+}

generate/testdata/QueryWithAlias.graphql

@@ -1 +1 @@
-{ User: user { ID: id } }
+query QueryWithAlias { User: user { ID: id } }

generate/testdata/QueryWithAlias.graphql.go

@@ -1,5 +1,29 @@
-type Response struct {
-	User *struct {
-		ID string
+package test
+
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type QueryWithAliasResponse struct {
+	User *User
+}
+
+type User struct {
+	ID string
+}
+
+func QueryWithAlias(client *graphql.Client) (*QueryWithAliasResponse, error) {
+	var retval QueryWithAliasResponse
+	err := client.MakeRequest(context.Background(), `
+query QueryWithAlias {
+	User: user {
+		ID: id
 	}
 }
+`, &retval, nil)
+	return &retval, err
+}

generate/testdata/QueryWithDoubleAlias.graphql

@@ -1,4 +1,4 @@
-{
+query QueryWithDoubleAlias {
   user {
     ID: id
     AlsoID: id

generate/testdata/QueryWithDoubleAlias.graphql.go

@@ -1,6 +1,31 @@
-type Response struct {
-	User *struct {
-		ID     string
-		AlsoID string
-	} `json:"user"`
-}
+package test
+
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type QueryWithDoubleAliasResponse struct {
+	User *User `json:"user"`
+}
+
+type User struct {
+	ID     string
+	AlsoID string
+}
+
+func QueryWithDoubleAlias(client *graphql.Client) (*QueryWithDoubleAliasResponse, error) {
+	var retval QueryWithDoubleAliasResponse
+	err := client.MakeRequest(context.Background(), `
+query QueryWithDoubleAlias {
+	user {
+		ID: id
+		AlsoID: id
+	}
+}
+`, &retval, nil)
+	return &retval, err
+}

generate/testdata/QueryWithEnums.graphql

@@ -1,4 +1,4 @@
-{
+query QueryWithEnums {
   user {
     roles
   }

generate/testdata/QueryWithEnums.graphql.go

@@ -1,12 +1,36 @@
-type Response struct {
-	User *struct {
-		Roles []role `json:"roles"`
-	} `json:"user"`
+package test
+
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type QueryWithEnumsResponse struct {
+	User *User `json:"user"`
 }
 
-type role string
+type Role string
 
 const (
-	studentRole role = "STUDENT"
-	teacherRole role = "TEACHER"
-)
+	StudentRole Role = "STUDENT"
+	TeacherRole Role = "TEACHER"
+)
+
+type User struct {
+	Roles []Role `json:"roles"`
+}
+
+func QueryWithEnums(client *graphql.Client) (*QueryWithEnumsResponse, error) {
+	var retval QueryWithEnumsResponse
+	err := client.MakeRequest(context.Background(), `
+query QueryWithEnums {
+	user {
+		roles
+	}
+}
+`, &retval, nil)
+	return &retval, err
+}

generate/testdata/QueryWithInput.graphql

@@ -1,4 +1,4 @@
-query ($query: UserQueryInput) {
+query QueryWithInput($query: UserQueryInput) {
   user(query: $query) {
     id
   }

generate/testdata/QueryWithInput.graphql.go

@@ -1,19 +1,47 @@
-type Response struct {
-	User *struct {
-		Id string `json:"id"`
-	} `json:"user"`
-}
+package test
 
-type role string
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
 
-const (
-	studentRole role = "STUDENT"
-	teacherRole role = "TEACHER"
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
 )
 
-type userQueryInput struct {
+type QueryWithInputResponse struct {
+	User *User `json:"user"`
+}
+
+type Role string
+
+const (
+	StudentRole Role = "STUDENT"
+	TeacherRole Role = "TEACHER"
+)
+
+type User struct {
+	Id string `json:"id"`
+}
+
+type UserQueryInput struct {
 	Email *string `json:"email"`
 	Name  *string `json:"name"`
 	Id    *string `json:"id"`
-	Role  *role   `json:"role"`
-}
+	Role  *Role   `json:"role"`
+}
+
+func QueryWithInput(client *graphql.Client, query *UserQueryInput) (*QueryWithInputResponse, error) {
+	variables := map[string]interface{}{
+		"query": query,
+	}
+
+	var retval QueryWithInputResponse
+	err := client.MakeRequest(context.Background(), `
+query QueryWithInput ($query: UserQueryInput) {
+	user(query: $query) {
+		id
+	}
+}
+`, &retval, variables)
+	return &retval, err
+}

generate/testdata/QueryWithSlices.graphql

@@ -1,4 +1,4 @@
-{
+query QueryWithSlices {
   user {
     emails
     emailsOrNull

generate/testdata/QueryWithSlices.graphql.go

@@ -1,8 +1,35 @@
-type Response struct {
-	User *struct {
-		Emails                []string  `json:"emails"`
-		EmailsOrNull          []string  `json:"emailsOrNull"`
-		EmailsWithNulls       []*string `json:"emailsWithNulls"`
-		EmailsWithNullsOrNull []*string `json:"emailsWithNullsOrNull"`
-	} `json:"user"`
-}
+package test
+
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type QueryWithSlicesResponse struct {
+	User *User `json:"user"`
+}
+
+type User struct {
+	Emails                []string  `json:"emails"`
+	EmailsOrNull          []string  `json:"emailsOrNull"`
+	EmailsWithNulls       []*string `json:"emailsWithNulls"`
+	EmailsWithNullsOrNull []*string `json:"emailsWithNullsOrNull"`
+}
+
+func QueryWithSlices(client *graphql.Client) (*QueryWithSlicesResponse, error) {
+	var retval QueryWithSlicesResponse
+	err := client.MakeRequest(context.Background(), `
+query QueryWithSlices {
+	user {
+		emails
+		emailsOrNull
+		emailsWithNulls
+		emailsWithNullsOrNull
+	}
+}
+`, &retval, nil)
+	return &retval, err
+}

generate/testdata/QueryWithStructs.graphql

@@ -1,4 +1,4 @@
-{
+query QueryWithStructs {
   user {
     authMethods {
       provider

generate/testdata/QueryWithStructs.graphql.go

@@ -1,8 +1,37 @@
-type Response struct {
-	User *struct {
-		AuthMethods []struct {
-			Provider *string `json:"provider"`
-			Email    *string `json:"email"`
-		} `json:"authMethods"`
-	} `json:"user"`
-}
+package test
+
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type AuthMethod struct {
+	Provider *string `json:"provider"`
+	Email    *string `json:"email"`
+}
+
+type QueryWithStructsResponse struct {
+	User *User `json:"user"`
+}
+
+type User struct {
+	AuthMethods []AuthMethod `json:"authMethods"`
+}
+
+func QueryWithStructs(client *graphql.Client) (*QueryWithStructsResponse, error) {
+	var retval QueryWithStructsResponse
+	err := client.MakeRequest(context.Background(), `
+query QueryWithStructs {
+	user {
+		authMethods {
+			provider
+			email
+		}
+	}
+}
+`, &retval, nil)
+	return &retval, err
+}

generate/testdata/SimpleQuery.graphql

@@ -1 +1 @@
-{ user { id } }
+query SimpleQuery { user { id } }

generate/testdata/SimpleQuery.graphql.go

@@ -1,5 +1,29 @@
-type Response struct {
-	User *struct {
-		Id string `json:"id"`
-	} `json:"user"`
+package test
+
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type SimpleQueryResponse struct {
+	User *User `json:"user"`
+}
+
+type User struct {
+	Id string `json:"id"`
+}
+
+func SimpleQuery(client *graphql.Client) (*SimpleQueryResponse, error) {
+	var retval SimpleQueryResponse
+	err := client.MakeRequest(context.Background(), `
+query SimpleQuery {
+	user {
+		id
+	}
+}
+`, &retval, nil)
+	return &retval, err
 }

generate/testdata/TypeName.graphql

@@ -1,4 +1,4 @@
-{
+query TypeNameQuery {
   user {
     __typename
     id

generate/testdata/TypeName.graphql.go

@@ -1,6 +1,31 @@
-type Response struct {
-	User *struct {
-		Typename *string `json:"__typename"`
-		Id       string  `json:"id"`
-	} `json:"user"`
-}
+package test
+
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type TypeNameQueryResponse struct {
+	User *User `json:"user"`
+}
+
+type User struct {
+	Typename *string `json:"__typename"`
+	Id       string  `json:"id"`
+}
+
+func TypeNameQuery(client *graphql.Client) (*TypeNameQueryResponse, error) {
+	var retval TypeNameQueryResponse
+	err := client.MakeRequest(context.Background(), `
+query TypeNameQuery {
+	user {
+		__typename
+		id
+	}
+}
+`, &retval, nil)
+	return &retval, err
+}

generate/testdata/UnionNoFragments.graphql

@@ -0,0 +1,5 @@
+query UnionNoFragmentsQuery {
+  randomLeaf {
+    __typename
+  }
+}

generate/testdata/UnionNoFragments.graphql.go

@@ -0,0 +1,79 @@
+package test
+
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type Article struct {
+	Typename *string `json:"__typename"`
+}
+
+func (v Article) implementsGraphQLInterfaceLeafContent() {}
+
+type LeafContent interface {
+	implementsGraphQLInterfaceLeafContent()
+}
+
+type UnionNoFragmentsQueryResponse struct {
+	RandomLeaf LeafContent `json:"-"`
+}
+
+func (v *UnionNoFragmentsQueryResponse) UnmarshalJSON(b []byte) error {
+	var firstPass struct {
+		*UnionNoFragmentsQueryResponse
+		RandomLeaf json.RawMessage `json:"randomLeaf"`
+	}
+	firstPass.UnionNoFragmentsQueryResponse = v
+
+	err := json.Unmarshal(b, &typenames)
+	if err != nil {
+		return err
+	}
+
+	var tn struct {
+		TypeName string `json:"__typename"`
+	}
+	err = json.Unmarshal(firstPass.RandomLeaf, &tn)
+	if err != nil {
+		return err
+	}
+	switch tn.TypeName {
+
+	case "Article":
+		v.RandomLeaf = Article{}
+		err = json.Unmarshal(
+			firstPass.RandomLeaf, &v.RandomLeaf)
+
+	case "Video":
+		v.RandomLeaf = Video{}
+		err = json.Unmarshal(
+			firstPass.RandomLeaf, &v.RandomLeaf)
+
+	}
+	if err != nil {
+		return err
+	}
+
+}
+
+type Video struct {
+	Typename *string `json:"__typename"`
+}
+
+func (v Video) implementsGraphQLInterfaceLeafContent() {}
+
+func UnionNoFragmentsQuery(client *graphql.Client) (*UnionNoFragmentsQueryResponse, error) {
+	var retval UnionNoFragmentsQueryResponse
+	err := client.MakeRequest(context.Background(), `
+query UnionNoFragmentsQuery {
+	randomLeaf {
+		__typename
+	}
+}
+`, &retval, nil)
+	return &retval, err
+}

generate/testdata/UsesEnumTwice.graphql

@@ -1,4 +1,4 @@
-{
+query UsesEnumTwiceQuery {
   Me: user { roles }
   OtherUser: user { roles }
 }

generate/testdata/UsesEnumTwice.graphql.go

@@ -1,15 +1,51 @@
-type Response struct {
-	Me *struct {
-		Roles []role `json:"roles"`
-	}
-	OtherUser *struct {
-		Roles []role `json:"roles"`
-	}
-}
+package test
 
-type role string
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type Role string
 
 const (
-	studentRole role = "STUDENT"
-	teacherRole role = "TEACHER"
-)
+	StudentRole Role = "STUDENT"
+	TeacherRole Role = "TEACHER"
+)
+
+type Role1 string
+
+const (
+	StudentRole1 Role1 = "STUDENT"
+	TeacherRole1 Role1 = "TEACHER"
+)
+
+type User struct {
+	Roles []Role `json:"roles"`
+}
+
+type User1 struct {
+	Roles []Role1 `json:"roles"`
+}
+
+type UsesEnumTwiceQueryResponse struct {
+	Me        *User
+	OtherUser *User1
+}
+
+func UsesEnumTwiceQuery(client *graphql.Client) (*UsesEnumTwiceQueryResponse, error) {
+	var retval UsesEnumTwiceQueryResponse
+	err := client.MakeRequest(context.Background(), `
+query UsesEnumTwiceQuery {
+	Me: user {
+		roles
+	}
+	OtherUser: user {
+		roles
+	}
+}
+`, &retval, nil)
+	return &retval, err
+}

generate/types.go

@@ -2,6 +2,7 @@ package generate
 
 import (
 	"fmt"
+	"strconv"
 	"strings"
 
 	"github.com/vektah/gqlparser/ast"
@@ -54,11 +55,16 @@ func (g *generator) addTypeForDefinition(nameOverride string, typ *ast.Definitio
 		name = nameOverride
 	} else {
 		// TODO: casing should be configurable
-		name = lowerFirst(typ.Name)
+		name = upperFirst(typ.Name)
 	}
 
-	if _, ok := g.typeMap[name]; ok {
-		return name, nil
+	// TODO: in some cases we can deduplicate, do that
+	// TODO: nicer naming scheme
+	i := 0
+	origName := name
+	for g.typeMap[name] != "" {
+		i++
+		name = origName + strconv.Itoa(i)
 	}
 
 	builder := &typeBuilder{typeName: name, generator: g}
@@ -73,22 +79,27 @@ func (g *generator) addTypeForDefinition(nameOverride string, typ *ast.Definitio
 }
 
 func (g *generator) getTypeForInputType(typ *ast.Type) (string, error) {
-	builder := &typeBuilder{typeName: lowerFirst(typ.Name()), generator: g}
-	err := builder.writeType(typ, selectionsForType(g, typ), false)
+	builder := &typeBuilder{typeName: upperFirst(typ.Name()), generator: g}
+	err := builder.writeType(typ, selectionsForType(g, typ))
 	return builder.String(), err
 }
 
+// TODO: this is really "field" now, rename it
 type selection interface {
 	Alias() string
-	Name() string
 	Type() *ast.Type
 	SelectionSet() ([]selection, error)
 }
 
 type field struct{ field *ast.Field }
 
-func (s field) Alias() string { return s.field.Alias }
-func (s field) Name() string  { return s.field.Name }
+func (s field) Alias() string {
+	if s.field.Alias != "" {
+		return s.field.Alias
+	}
+	// TODO: is this case needed? tests don't seem to get here.
+	return s.field.Name
+}
 
 func (s field) Type() *ast.Type {
 	if s.field.Definition == nil {
@@ -122,7 +133,6 @@ type inputField struct {
 }
 
 func (s inputField) Alias() string   { return s.field.Name }
-func (s inputField) Name() string    { return s.field.Name }
 func (s inputField) Type() *ast.Type { return s.field.Type }
 
 func (s inputField) SelectionSet() ([]selection, error) {
@@ -139,13 +149,7 @@ func selectionsForType(g *generator, typ *ast.Type) []selection {
 }
 
 func (builder *typeBuilder) writeField(selection selection) error {
-	var jsonName string
-	if selection.Alias() != "" {
-		jsonName = selection.Alias()
-	} else {
-		// TODO: is this case needed? tests don't seem to get here.
-		jsonName = selection.Name()
-	}
+	jsonName := selection.Alias()
 	// We need an exportable name for JSON-marshaling.
 	goName := upperFirst(jsonName)
 
@@ -156,7 +160,7 @@ func (builder *typeBuilder) writeField(selection selection) error {
 	if typ == nil {
 		// Unclear why gqlparser hasn't already rejected this,
 		// but empirically it might not.
-		return fmt.Errorf("undefined field %v", selection.Name())
+		return fmt.Errorf("undefined field %v", selection.Alias())
 	}
 
 	selectionSet, err := selection.SelectionSet()
@@ -164,12 +168,15 @@ func (builder *typeBuilder) writeField(selection selection) error {
 		return err
 	}
 
-	err = builder.writeType(typ, selectionSet, true)
+	err = builder.writeType(typ, selectionSet)
 	if err != nil {
 		return err
 	}
 
-	if jsonName != goName {
+	if builder.schema.Types[typ.Name()].IsAbstractType() {
+		// abstract types are handled in our UnmarshalJSON
+		builder.WriteString(" `json:\"-\"`")
+	} else if jsonName != goName {
 		fmt.Fprintf(builder, " `json:\"%s\"`", jsonName)
 	}
 	builder.WriteRune('\n')
@@ -184,7 +191,7 @@ var builtinTypes = map[string]string{
 	"ID":      "string", // TODO: named type for IDs?
 }
 
-func (builder *typeBuilder) writeType(typ *ast.Type, selectionSet []selection, inline bool) error {
+func (builder *typeBuilder) writeType(typ *ast.Type, selectionSet []selection) error {
 	// gqlgen does slightly different things here since it defines names for
 	// all the intermediate types, but its implementation may be useful to crib
 	// from:
@@ -200,16 +207,6 @@ func (builder *typeBuilder) writeType(typ *ast.Type, selectionSet []selection, i
 	}
 
 	def := builder.schema.Types[typ.Name()]
-	// TODO: set inline = false for nested types
-	switch def.Kind {
-	case ast.Scalar, ast.Enum, ast.Union, ast.Interface:
-		inline = false
-	}
-
-	if inline {
-		return builder.writeTypedef(def, selectionSet)
-	}
-
 	// Writes a typedef elsewhere (if not already defined)
 	name, err := builder.addTypeForDefinition("", def, selectionSet)
 	if err != nil {
@@ -231,7 +228,35 @@ func (builder *typeBuilder) writeTypedef(typedef *ast.Definition, selectionSet [
 			}
 		}
 		builder.WriteString("}")
+
+		// If any field is abstract, we need an UnmarshalJSON method to handle
+		// it.
+		return builder.maybeWriteUnmarshal(selectionSet)
+
+	case ast.Interface, ast.Union:
+		// First, write the interface type.
+		builder.WriteString("interface {\n")
+		implementsMethodName := fmt.Sprintf("implementsGraphQLInterface%v", builder.typeName)
+		// TODO: Also write GetX() accessor methods for fields of the interface
+		builder.WriteString(implementsMethodName)
+		builder.WriteString("()\n")
+		builder.WriteString("}")
+
+		// Then, write the implementations.
+		// TODO(benkraft): Put a doc-comment somewhere with the list.
+		for _, impldef := range builder.schema.GetPossibleTypes(typedef) {
+			name, err := builder.addTypeForDefinition("", impldef, selectionSet)
+			if err != nil {
+				return err
+			}
+
+			// HACK HACK HACK
+			builder.typeMap[name] += fmt.Sprintf(
+				"\nfunc (v %v) %v() {}", name, implementsMethodName)
+		}
+
 		return nil
+
 	case ast.Enum:
 		// All GraphQL enums have underlying type string (in the Go sense).
 		builder.WriteString("string\n")
@@ -244,8 +269,8 @@ func (builder *typeBuilder) writeTypedef(typedef *ast.Definition, selectionSet [
 		}
 		builder.WriteString(")\n")
 		return nil
-	case ast.Scalar, ast.Union, ast.Interface:
-		// TODO(benkraft): Handle custom scalars, unions, and interfaces.
+	case ast.Scalar:
+		// TODO(benkraft): Handle custom scalars.
 		return fmt.Errorf("not implemented: %v", typedef.Kind)
 	default:
 		return fmt.Errorf("unexpected kind: %v", typedef.Kind)

generate/types_test.go

@@ -55,8 +55,6 @@ func TestTypeForOperation(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	schemaText := readFile(t, "schema.graphql", false)
-
 	for _, file := range files {
 		graphqlFilename := file.Name()
 		if graphqlFilename == "schema.graphql" || !strings.HasSuffix(graphqlFilename, ".graphql") {
@@ -65,45 +63,25 @@ func TestTypeForOperation(t *testing.T) {
 		goFilename := graphqlFilename + ".go"
 
 		t.Run(graphqlFilename, func(t *testing.T) {
-			expectedGoType, err := gofmt(readFile(t, goFilename, update))
+			expectedGoCode, err := gofmt(readFile(t, goFilename, update))
 			if err != nil {
 				t.Fatal(err)
 			}
 
-			schema, graphqlError := gqlparser.LoadSchema(
-				&ast.Source{Name: "test schema", Input: schemaText})
-			if graphqlError != nil {
-				t.Fatal(graphqlError)
-			}
-
-			queryDoc, graphqlListError := gqlparser.LoadQuery(
-				schema, readFile(t, graphqlFilename, false))
-			if graphqlListError != nil {
-				t.Fatal(graphqlListError)
-			}
-
-			if len(queryDoc.Operations) != 1 {
-				t.Fatalf("got %v operations, want 1", len(queryDoc.Operations))
-			}
-
-			g := newGenerator(&Config{Package: "test_package"}, schema)
-			err = g.addOperation(queryDoc.Operations[0])
+			goCode, err := Generate(&Config{
+				Schema:  filepath.Join("testdata", "schema.graphql"),
+				Queries: filepath.Join("testdata", graphqlFilename),
+				Package: "test",
+			})
 			if err != nil {
-				t.Error(err)
+				t.Fatal(err)
 			}
 
-			// gofmt before comparing.
-			goType, err := gofmt(g.Types())
-			if err != nil {
-				t.Error(err)
-			}
-
-			if goType != expectedGoType {
-				t.Errorf("got:\n%v\nwant:\n%v\n", goType, expectedGoType)
+			if string(goCode) != expectedGoCode {
+				t.Errorf("got:\n%v\nwant:\n%v\n", string(goCode), expectedGoCode)
 				if update {
 					t.Log("Updating testdata dir to match")
-					err = ioutil.WriteFile(
-						filepath.Join(dataDir, goFilename), []byte(goType), 0644)
+					err = ioutil.WriteFile(filepath.Join(dataDir, goFilename), goCode, 0644)
 					if err != nil {
 						t.Errorf("Unable to update testdata dir: %v", err)
 					}
@@ -138,18 +116,18 @@ func TestTypeForInputType(t *testing.T) {
 	}, {
 		`DefinedType`,
 		`UserQueryInput`,
-		`*userQueryInput`,
+		`*UserQueryInput`,
 		[]string{
-			`type role string
+			`type Role string
 			const (
-				studentRole role = "STUDENT"
-				teacherRole role = "TEACHER"
+				StudentRole Role = "STUDENT"
+				TeacherRole Role = "TEACHER"
 			)`,
-			`type userQueryInput struct {
+			`type UserQueryInput struct {
 				Email    *string ` + "`json:\"email\"`" + `
 				Name     *string ` + "`json:\"name\"`" + `
 				Id       *string ` + "`json:\"id\"`" + `
-				Role     *role   ` + "`json:\"role\"`" + `
+				Role     *Role   ` + "`json:\"role\"`" + `
 			}`,
 		},
 	}}

generate/unmarshal.go

@@ -0,0 +1,51 @@
+package generate
+
+var unmarshalTemplate = mustTemplate("unmarshal.go.tmpl")
+
+type templateData struct {
+	// Go type to which the method will be added
+	Type string
+	// Abstract fields of the type, which need special handling.
+	Fields []abstractField
+}
+
+type abstractField struct {
+	// Name of the field, in Go and JSON
+	GoName, JSONName string
+	// Concrete types the field might take.
+	ConcreteTypes []concreteType
+}
+
+type concreteType struct {
+	// Name of the type, in Go and GraphQL
+	GoName, GraphQLName string
+}
+
+func (builder *typeBuilder) maybeWriteUnmarshal(fields []selection) error {
+	data := templateData{Type: builder.typeName}
+	for _, field := range fields {
+		typedef := builder.schema.Types[field.Type().Name()]
+		if typedef.IsAbstractType() {
+			fieldInfo := abstractField{
+				GoName:   upperFirst(field.Alias()),
+				JSONName: field.Alias(),
+			}
+			for _, typedef := range builder.schema.GetPossibleTypes(typedef) {
+				fieldInfo.ConcreteTypes = append(fieldInfo.ConcreteTypes,
+					concreteType{
+						// TODO: lies!  We might have added "1" or something.
+						GoName:      upperFirst(typedef.Name),
+						GraphQLName: typedef.Name,
+					})
+			}
+			data.Fields = append(data.Fields, fieldInfo)
+		}
+	}
+
+	if len(data.Fields) == 0 {
+		return nil
+	}
+
+	builder.WriteString("\n\n")
+	return unmarshalTemplate.Execute(builder, data)
+}

generate/unmarshal.go.tmpl

@@ -0,0 +1,35 @@
+func (v *{{.Type}}) UnmarshalJSON(b []byte) error {
+	var firstPass struct{
+		*{{.Type}}
+        {{range .Fields -}}
+		{{.GoName}} json.RawMessage `json:"{{.JSONName}}"`
+        {{end}}
+	}
+	firstPass.{{.Type}} = v
+
+	err := json.Unmarshal(b, &typenames)
+    if err != nil {
+        return err
+    }
+
+    {{range .Fields -}}
+	var tn struct { TypeName string `json:"__typename"` }
+	err = json.Unmarshal(firstPass.{{.GoName}}, &tn)
+    if err != nil {
+        return err
+    }
+	switch tn.TypeName {
+    {{with $field := .}}
+    {{range $field.ConcreteTypes}}
+	case "{{.GraphQLName}}":
+		v.{{$field.GoName}} = {{.GoName}}{}
+		err = json.Unmarshal(
+			firstPass.{{$field.GoName}}, &v.{{$field.GoName}})
+    {{end}}
+    {{end}}
+	}
+    if err != nil {
+        return err
+    }
+    {{end}}
+}

generate/util.go

@@ -29,14 +29,15 @@ func upperFirst(s string) string {
 }
 
 func goConstName(s string) string {
+	if strings.TrimLeft(s, "_") == "" {
+		return s
+	}
 	var prev rune
 	return strings.Map(func(r rune) rune {
 		var ret rune
-		if prev == 0 && r == '_' {
-			return '_' // still treat next char as first
-		} else if r == '_' {
+		if r == '_' {
 			ret = -1
-		} else if prev == '_' {
+		} else if prev == '_' || prev == 0 {
 			ret = unicode.ToUpper(r)
 		} else {
 			ret = unicode.ToLower(r)

generate/util_test.go

@@ -55,10 +55,10 @@ func TestUpperFirst(t *testing.T) {
 func TestGoConstName(t *testing.T) {
 	tests := []test{
 		{"Empty", "", ""},
-		{"AllCaps", "ASDF", "asdf"},
-		{"AllCapsWithUnderscore", "ASDF_GH", "asdfGh"},
+		{"AllCaps", "ASDF", "Asdf"},
+		{"AllCapsWithUnderscore", "ASDF_GH", "AsdfGh"},
 		{"JustUnderscore", "_", "_"},
-		{"LeadingUnderscore", "_ASDF_GH", "_asdfGh"},
+		{"LeadingUnderscore", "_ASDF_GH", "AsdfGh"},
 	}
 
 	testStringFunc(t, goConstName, tests)