allow interface{} as a scalar

generate/generate_test.go

@@ -74,6 +74,7 @@ func TestGenerate(t *testing.T) {
 				Scalars: map[string]string{
 					"ID":       "github.com/me/mypkg.ID",
 					"DateTime": "time.Time",
+					"Junk":     "interface{}",
 				},
 			})
 			if err != nil {

generate/imports.go

@@ -39,7 +39,12 @@ func (g *generator) ref(fullyQualifiedName string) (qualifiedName string, err er
 func (g *generator) getRef(fullyQualifiedName string, addImport bool) (qualifiedName string, err error) {
 	i := strings.LastIndex(fullyQualifiedName, ".")
 	if i == -1 {
-		if types.Universe.Lookup(fullyQualifiedName) == nil {
+		// We allow any builtin type, or interface{}.  In principle it would be
+		// fine to allow any interface or struct, but (1) they might refer to a
+		// type that needs an import, and (2) that just honestly seems
+		// confusing, why would you want it.  But the empty interface,
+		// specifically, is useful.
+		if fullyQualifiedName != "interface{}" && types.Universe.Lookup(fullyQualifiedName) == nil {
 			return "", fmt.Errorf(
 				`unknown name "%v"; expected a builtin or path/to/package.Name`, fullyQualifiedName)
 		}

generate/testdata/queries/EmptyInterface.graphql

@@ -0,0 +1 @@
+query EmptyInterface { getJunk }

generate/testdata/queries/EmptyInterface.graphql.go

@@ -0,0 +1,29 @@
+package test
+
+// Code generated by github.com/Khan/genqlient, DO NOT EDIT.
+
+import (
+	"github.com/Khan/genqlient/graphql"
+)
+
+type EmptyInterfaceResponse struct {
+	GetJunk interface{} `json:"getJunk"`
+}
+
+func EmptyInterface(
+	client graphql.Client,
+) (*EmptyInterfaceResponse, error) {
+	var retval EmptyInterfaceResponse
+	err := client.MakeRequest(
+		nil,
+		"EmptyInterface",
+		`
+query EmptyInterface {
+	getJunk
+}
+`,
+		&retval,
+		nil,
+	)
+	return &retval, err
+}

generate/testdata/queries/EmptyInterface.graphql.json

@@ -0,0 +1,9 @@
+{
+  "operations": [
+    {
+      "operationName": "EmptyInterface",
+      "query": "\nquery EmptyInterface {\n\tgetJunk\n}\n",
+      "sourceLocation": "testdata/queries/EmptyInterface.graphql"
+    }
+  ]
+}

generate/testdata/queries/schema.graphql

@@ -1,5 +1,7 @@
 scalar DateTime
 
+scalar Junk
+
 enum Role {
   STUDENT
   TEACHER
@@ -64,6 +66,7 @@ type Query {
   randomLeaf: LeafContent!
   convert(dt: DateTime!, tz: String): DateTime!
   maybeConvert(dt: DateTime, tz: String): DateTime
+  getJunk: Junk
 }
 
 type Mutation {