Renaming Entity in gqlgen to avoid type name conflict

Addresses 99designs#1256

README.md

@@ -1,3 +1,21 @@
+# Grand Rounds Fork of GQLgen
+
+This fork was created by:
+
+1. Forking the repository
+2. Resetting master of the fork to the tagged commit of the last stable release
+   of gqlgen. At the time of writing this, it's tag v0.13.0 and commit 07c1f93.
+3. Pushing -f to reset master of this fork the above commit.
+3. Opening a pull request of the patch we've applied, to this fork, and merging
+   the patch into the master branch of this fork.s
+
+Note that means the master branch of this fork diverges from the official
+repository. To update this fork to the latest version of gqlgen:
+
+1. Merge the latest version tagged commit of upstream into master of this fork.
+   **Don't** merge in the master branch of the main repository, just the commit
+   of the next tagged version.
+
 # gqlgen [![Continuous Integration](https://github.com/99designs/gqlgen/workflows/Continuous%20Integration/badge.svg)](https://github.com/99designs/gqlgen/actions) [![Read the Docs](https://badgen.net/badge/docs/available/green)](http://gqlgen.com/) [![GoDoc](https://godoc.org/github.com/99designs/gqlgen?status.svg)](https://godoc.org/github.com/99designs/gqlgen)
 
 ![gqlgen](https://user-images.githubusercontent.com/46195831/89802919-0bb8ef00-db2a-11ea-8ba4-88e7a58b2fd2.png)

codegen/templates/templates.go

@@ -282,10 +282,25 @@ func Call(p *types.Func) string {
 	return pkg + p.Name()
 }
 
+// Federated graphs have the types _Entity and _Service. With default Go struct
+// name generation, those become `Service`, which can conflict with users
+// of this library who have their own `type Service`. Special case handle the
+// federated entity names
+var internalNames = map[string]string{
+	"_Entity":  "GqlgenEntity",
+	"_Service": "GqlgenService",
+}
+
 func ToGo(name string) string {
 	if name == "_" {
 		return "_"
 	}
+
+	internalName, hasInternalName := internalNames[name]
+	if hasInternalName {
+		return internalName
+	}
+
 	runes := make([]rune, 0, len(name))
 
 	wordWalker(name, func(info *wordInfo) {

codegen/templates/templates_test.go

@@ -38,6 +38,11 @@ func TestToGo(t *testing.T) {
 	require.Equal(t, "RelatedUrls", ToGo("RelatedUrls"))
 	require.Equal(t, "ITicket", ToGo("ITicket"))
 	require.Equal(t, "FooTicket", ToGo("fooTicket"))
+
+	require.Equal(t, "GqlgenEntity", ToGo("_Entity"))
+	require.Equal(t, "GqlgenService", ToGo("_Service"))
+	require.Equal(t, "Entity", ToGo("Entity"))
+	require.Equal(t, "Service", ToGo("Service"))
 }
 
 func TestToGoPrivate(t *testing.T) {