total rewrite to interface handling; not complete but it compiles

generate/testdata/InterfaceNoFragments.graphql.go

@@ -0,0 +1,97 @@
+package test
+
+// Code generated by github.com/Khan/genql, DO NOT EDIT.
+
+import (
+	"context"
+
+	"github.com/Khan/genql/graphql"
+)
+
+type Article struct {
+	Id   string `json:"id"`
+	Name string `json:"name"`
+}
+
+func (v Article) implementsGraphQLInterfaceContent() {}
+
+type Content interface {
+	implementsGraphQLInterfaceContent()
+}
+
+type InterfaceNoFragmentsQueryResponse struct {
+	Root Topic `json:"root"`
+}
+
+type Topic struct {
+	Id       string    `json:"id"`
+	Name     string    `json:"name"`
+	Children []Content `json:"-"`
+}
+
+func (v *Topic) UnmarshalJSON(b []byte) error {
+	var firstPass struct {
+		*Topic
+		Children json.RawMessage `json:"children"`
+	}
+	firstPass.Topic = v
+
+	err := json.Unmarshal(b, &typenames)
+	if err != nil {
+		return err
+	}
+
+	var tn struct {
+		TypeName string `json:"__typename"`
+	}
+	err = json.Unmarshal(firstPass.Children, &tn)
+	if err != nil {
+		return err
+	}
+	switch tn.TypeName {
+
+	case "Article":
+		v.Children = Article{}
+		err = json.Unmarshal(
+			firstPass.Children, &v.Children)
+
+	case "Video":
+		v.Children = Video{}
+		err = json.Unmarshal(
+			firstPass.Children, &v.Children)
+
+	case "Topic":
+		v.Children = Topic{}
+		err = json.Unmarshal(
+			firstPass.Children, &v.Children)
+
+	}
+	if err != nil {
+		return err
+	}
+
+}
+
+type Video struct {
+	Id   string `json:"id"`
+	Name string `json:"name"`
+}
+
+func (v Video) implementsGraphQLInterfaceContent() {}
+
+func InterfaceNoFragmentsQuery(client *graphql.Client) (*InterfaceNoFragmentsQueryResponse, error) {
+	var retval InterfaceNoFragmentsQueryResponse
+	err := client.MakeRequest(context.Background(), `
+query InterfaceNoFragmentsQuery {
+	root {
+		id
+		name
+		children {
+			id
+			name
+		}
+	}
+}
+`, &retval, nil)
+	return &retval, err
+}