Trim underscores from around go identifiers

codegen/templates/templates.go

@@ -276,6 +276,9 @@ func Call(p *types.Func) string {
 }
 
 func ToGo(name string) string {
+	if name == "_" {
+		return "_"
+	}
 	runes := make([]rune, 0, len(name))
 
 	wordWalker(name, func(info *wordInfo) {
@@ -296,6 +299,9 @@ func ToGo(name string) string {
 }
 
 func ToGoPrivate(name string) string {
+	if name == "_" {
+		return "_"
+	}
 	runes := make([]rune, 0, len(name))
 
 	first := true
@@ -331,7 +337,7 @@ type wordInfo struct {
 // This function is based on the following code.
 // https://github.com/golang/lint/blob/06c8688daad7faa9da5a0c2f163a3d14aac986ca/lint.go#L679
 func wordWalker(str string, f func(*wordInfo)) {
-	runes := []rune(str)
+	runes := []rune(strings.TrimFunc(str, isDelimiter))
 	w, i := 0, 0 // index of start of word, scan
 	hasCommonInitial := false
 	for i+1 <= len(runes) {

codegen/templates/templates_test.go

@@ -16,6 +16,9 @@ func TestToGo(t *testing.T) {
 	require.Equal(t, "ToCamel", ToGo("toCamel"))
 	require.Equal(t, "ToCamel", ToGo("ToCamel"))
 	require.Equal(t, "ToCamel", ToGo("to-camel"))
+	require.Equal(t, "ToCamel", ToGo("-to-camel"))
+	require.Equal(t, "ToCamel", ToGo("_to-camel"))
+	require.Equal(t, "_", ToGo("_"))
 
 	require.Equal(t, "RelatedURLs", ToGo("RelatedURLs"))
 	require.Equal(t, "ImageIDs", ToGo("ImageIDs"))
@@ -63,6 +66,7 @@ func TestToGoPrivate(t *testing.T) {
 	require.Equal(t, "id", ToGoPrivate("ID"))
 	require.Equal(t, "id", ToGoPrivate("id"))
 	require.Equal(t, "", ToGoPrivate(""))
+	require.Equal(t, "_", ToGoPrivate("_"))
 }
 
 func Test_wordWalker(t *testing.T) {

example/federation/reviews/graph/model/models.go

@@ -4,7 +4,7 @@ type Product struct {
 	Upc string `json:"upc"`
 }
 
-func (Product) Is_Entity() {}
+func (Product) IsEntity() {}
 
 type Review struct {
 	Body    string
@@ -16,4 +16,4 @@ type User struct {
 	ID string `json:"id"`
 }
 
-func (User) Is_Entity() {}
+func (User) IsEntity() {}

plugin/federation/fedruntime/runtime.go

@@ -9,5 +9,5 @@ type Service struct {
 
 // Everything with a @key implements this
 type Entity interface {
-	Is_Entity()
+	IsEntity()
 }

plugin/modelgen/models_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 
 	"github.com/99designs/gqlgen/codegen/config"
+	"github.com/99designs/gqlgen/plugin/modelgen/out"
 	"github.com/stretchr/testify/require"
 )
 
@@ -63,6 +64,10 @@ func TestModelGeneration(t *testing.T) {
 			require.True(t, strings.Contains(fileText, tag))
 		}
 	})
+
+	t.Run("concrete types implement interface", func(t *testing.T) {
+		var _ out.FooBarer = out.FooBarr{}
+	})
 }
 
 func mutateHook(b *ModelBuild) *ModelBuild {

plugin/modelgen/testdata/schema.graphql

@@ -83,3 +83,12 @@ interface InterfaceWithDescription {
 
 "UnionWithDescription is an union with a description"
 union UnionWithDescription = TypeWithDescription | ExistingType
+
+
+interface Foo_Barer {
+    name: String!
+}
+
+type _Foo_Barr implements  Foo_Barer {
+    name: String!
+}