Add support for interfaces, part 1: the simplest cases

generate/config.go

@@ -73,6 +73,13 @@ type Config struct {
 	// and UnmarshalJSON methods, or otherwise be convertible to JSON.
 	Scalars map[string]string `yaml:"scalars"`
 
+	// Set to true to use features that aren't fully ready to use.
+	//
+	// This is primarily intended for genqlient's own tests.  These features
+	// are likely BROKEN and come with NO EXPECTATION OF COMPATIBBILITY.  Use
+	// them at your own risk!
+	AllowBrokenFeatures bool `yaml:"allow_broken_features"`
+
 	// Set automatically to the filename of the config file itself.
 	configFilename string
 }

generate/convert.go

@@ -25,7 +25,7 @@ func (g *generator) baseTypeForOperation(operation ast.Operation) (*ast.Definiti
 	case ast.Mutation:
 		return g.schema.Mutation, nil
 	case ast.Subscription:
-		if !allowBrokenFeatures {
+		if !g.Config.AllowBrokenFeatures {
 			return nil, errorf(nil, "genqlient does not yet support subscriptions")
 		}
 		return g.schema.Subscription, nil
@@ -255,10 +255,23 @@ func (g *generator) convertDefinition(
 		return goType, nil
 
 	case ast.Interface, ast.Union:
-		if !allowBrokenFeatures {
+		if !g.Config.AllowBrokenFeatures {
 			return nil, errorf(pos, "not implemented: %v", def.Kind)
 		}
 
+		// We need to request __typename so we know which concrete type to use.
+		hasTypename := false
+		for _, selection := range selectionSet {
+			field, ok := selection.(*ast.Field)
+			if ok && field.Name == "__typename" {
+				hasTypename = true
+			}
+		}
+		if !hasTypename {
+			// TODO(benkraft): Instead, modify the query to add __typename.
+			return nil, errorf(pos, "union/interface type %s must request __typename", def.Name)
+		}
+
 		implementationTypes := g.schema.GetPossibleTypes(def)
 		goType := &goInterfaceType{
 			GoName:          name,

generate/generate.go

@@ -17,9 +17,6 @@ import (
 	"golang.org/x/tools/imports"
 )
 
-// Set to true to test features that aren't yet really ready.
-var allowBrokenFeatures = false
-
 // generator is the context for the codegen process (and ends up getting passed
 // to the template).
 type generator struct {
@@ -230,7 +227,7 @@ func Generate(config *Config) (map[string][]byte, error) {
 			strings.Join(config.Operations, ", "))
 	}
 
-	if len(document.Fragments) > 0 && !allowBrokenFeatures {
+	if len(document.Fragments) > 0 && !config.AllowBrokenFeatures {
 		return nil, errorf(document.Fragments[0].Position,
 			"genqlient does not yet support fragments")
 	}

generate/generate_test.go

@@ -30,9 +30,6 @@ const (
 // update the snapshots.  Make sure to check that the output is sensible; the
 // snapshots don't even get compiled!
 func TestGenerate(t *testing.T) {
-	// we can test parts of features even if they're not done yet!
-	allowBrokenFeatures = true
-
 	files, err := ioutil.ReadDir(dataDir)
 	if err != nil {
 		t.Fatal(err)
@@ -59,6 +56,7 @@ func TestGenerate(t *testing.T) {
 					"Junk":        "interface{}",
 					"ComplexJunk": "[]map[string]*[]*map[string]interface{}",
 				},
+				AllowBrokenFeatures: true,
 			})
 			if err != nil {
 				t.Fatal(err)
@@ -74,9 +72,12 @@ func TestGenerate(t *testing.T) {
 				if testing.Short() {
 					t.Skip("skipping build due to -short")
 				} else if sourceFilename == "InterfaceNesting.graphql" ||
-					sourceFilename == "InterfaceNoFragments.graphql" ||
-					sourceFilename == "Omitempty.graphql" {
-					t.Skip("TODO: enable these once they build")
+					sourceFilename == "InterfaceListField.graphql" {
+					t.Skip("TODO: enable after fixing " +
+						"https://github.com/Khan/genqlient/issues/8")
+				} else if sourceFilename == "Omitempty.graphql" {
+					t.Skip("TODO: enable after fixing " +
+						"https://github.com/Khan/genqlient/issues/43")
 				}
 
 				goContent := generated[goFilename]
@@ -109,9 +110,6 @@ func TestGenerate(t *testing.T) {
 }
 
 func TestGenerateErrors(t *testing.T) {
-	// we can test parts of features even if they're not done yet!
-	allowBrokenFeatures = true
-
 	files, err := ioutil.ReadDir(errorsDir)
 	if err != nil {
 		t.Fatal(err)
@@ -138,6 +136,7 @@ func TestGenerateErrors(t *testing.T) {
 					"ValidScalar":   "string",
 					"InvalidScalar": "bogus",
 				},
+				AllowBrokenFeatures: true,
 			})
 			if err == nil {
 				t.Fatal("expected an error")

generate/testdata/errors/MissingTypeName.go

@@ -0,0 +1,5 @@
+package errors
+
+const _ = `# @genqlient
+	query MyQuery { i { f } }
+`

generate/testdata/errors/MissingTypeName.graphql

@@ -0,0 +1 @@
+query MyQuery { i { f } }

generate/testdata/errors/MissingTypeName.schema.graphql

@@ -0,0 +1,11 @@
+type Query {
+  i: I
+}
+
+type T implements I {
+  f: String!
+}
+
+interface I {
+  f: String!
+}

generate/testdata/queries/InterfaceListField.graphql

@@ -0,0 +1,11 @@
+query InterfaceNoFragmentsQuery {
+  root {
+    id
+    name
+    children {
+      __typename
+      id
+      name
+    }
+  }
+}

generate/testdata/queries/InterfaceNesting.graphql

@@ -2,10 +2,13 @@ query InterfaceNesting {
   root {
     id
     children {
+      __typename
       id
       parent {
+        __typename
         id
         children {
+          __typename
           id
         }
       }

generate/testdata/queries/InterfaceNoFragments.graphql

@@ -1,10 +1,4 @@
 query InterfaceNoFragmentsQuery {
-  root {
-    id
-    name
-    children {
-      id
-      name
-    }
-  }
+  root { id name }       # (make sure sibling fields work)
+  randomItem { __typename id name }
 }

generate/testdata/queries/schema.graphql

@@ -104,6 +104,7 @@ type Query {
   """usersWithRole looks a user up by role."""
   usersWithRole(role: Role!): [User!]!
   root: Topic!
+  randomItem: Content!
   randomLeaf: LeafContent!
   convert(dt: DateTime!, tz: String): DateTime!
   maybeConvert(dt: DateTime, tz: String): DateTime

generate/testdata/snapshots/TestGenerate-InterfaceListField.graphql-InterfaceListField.graphql.json

@@ -0,0 +1,9 @@
+{
+  "operations": [
+    {
+      "operationName": "InterfaceNoFragmentsQuery",
+      "query": "\nquery InterfaceNoFragmentsQuery {\n\troot {\n\t\tid\n\t\tname\n\t\tchildren {\n\t\t\t__typename\n\t\t\tid\n\t\t\tname\n\t\t}\n\t}\n}\n",
+      "sourceLocation": "testdata/queries/InterfaceListField.graphql"
+    }
+  ]
+}