From ddf4b03350c7ef1fb1ed0d0f0be2b2a9f83a93c6 Mon Sep 17 00:00:00 2001
From: Ben Kraft <benkraft@khanacademy.org>
Date: Thu, 15 Apr 2021 11:50:52 -0700
Subject: [PATCH] allow interface{} as a scalar

---
 generate/generate_test.go                     |  1 +
 generate/imports.go                           |  7 ++++-
 .../testdata/queries/EmptyInterface.graphql   |  1 +
 .../queries/EmptyInterface.graphql.go         | 29 +++++++++++++++++++
 .../queries/EmptyInterface.graphql.json       |  9 ++++++
 generate/testdata/queries/schema.graphql      |  3 ++
 6 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 generate/testdata/queries/EmptyInterface.graphql
 create mode 100644 generate/testdata/queries/EmptyInterface.graphql.go
 create mode 100644 generate/testdata/queries/EmptyInterface.graphql.json

diff --git a/generate/generate_test.go b/generate/generate_test.go
index a0df9e9..6476641 100644
--- a/generate/generate_test.go
+++ b/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 {
diff --git a/generate/imports.go b/generate/imports.go
index 58acece..50f64dc 100644
--- a/generate/imports.go
+++ b/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)
 		}
diff --git a/generate/testdata/queries/EmptyInterface.graphql b/generate/testdata/queries/EmptyInterface.graphql
new file mode 100644
index 0000000..30ede1d
--- /dev/null
+++ b/generate/testdata/queries/EmptyInterface.graphql
@@ -0,0 +1 @@
+query EmptyInterface { getJunk }
diff --git a/generate/testdata/queries/EmptyInterface.graphql.go b/generate/testdata/queries/EmptyInterface.graphql.go
new file mode 100644
index 0000000..80cafd4
--- /dev/null
+++ b/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
+}
diff --git a/generate/testdata/queries/EmptyInterface.graphql.json b/generate/testdata/queries/EmptyInterface.graphql.json
new file mode 100644
index 0000000..cb71e68
--- /dev/null
+++ b/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"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/generate/testdata/queries/schema.graphql b/generate/testdata/queries/schema.graphql
index bb8e9c1..987a633 100644
--- a/generate/testdata/queries/schema.graphql
+++ b/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 {