Encode and decode fields of union type.

mojom/generators/go/templates/encoding.go

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package templates
 
 import (
         "text/template"
 )
 
 const fieldEncodingTmplText = `
 {{- define "FieldEncodingTmpl" -}}
 {{- $info := . -}}
-{{- if $info.IsNullable -}}
+{{- if and (not $info.IsUnion) $info.IsNullable -}}
 if {{$info.Identifier}} == nil {
 {{- if $info.IsPointer -}}
         encoder.WriteNullPointer()
 {{- else if $info.IsHandle -}}
         encoder.WriteInvalidHandle()
 {{- end -}}
 } else {
         {{ template "NonNullableFieldEncodingTmpl" $info }}
 }
 {{- else -}}
@@ skipping 19 matching lines @@
 if err := encoder.WriteHandle(*({{$info.Identifier}})); err != nil {
 {{- else -}}
 if err := encoder.WriteHandle({{$info.Identifier}}); err != nil {
 {{- end -}}
         return err
 }
 {{- else if $info.IsStruct -}}
 if err := {{$info.Identifier}}.Encode(encoder); err != nil {
         return err
 }
+{{- else if $info.IsUnion -}}
+{{- if $info.IsPointer -}}
+encoder.StartNestedUnion()
+{{end -}}
+if {{$info.Identifier}} == nil {
+{{- if $info.IsNullable -}}
+        encoder.WriteNullUnion()
+{{- else -}}
+        return &bindings.ValidationError{bindings.UnexpectedNullUnion, "unexpected null union"}
+{{- end -}}
+} else {
+        if err := {{$info.Identifier}}.Encode(encoder); err != nil {
+                return err
+        }
+}
 {{- else if $info.IsArray -}}
 {{ $elInfo := $info.ElementEncodingInfo -}}
 encoder.StartArray(uint32(len({{$info.Identifier}})), {{$elInfo.BitSize}})
 for _, {{$elInfo.Identifier}} := range {{$info.Identifier}} {
         {{ template "FieldEncodingTmpl" $elInfo }}
 }
 if err := encoder.Finish(); err != nil {
         return err
 }
 {{- else if $info.IsMap -}}
@@ skipping 21 matching lines @@
         return err
 }
 {{- end -}}
 {{- end -}}
 `
 
 func initEncodingTemplates() {
         template.Must(goFileTmpl.Parse(nonNullableFieldEncodingTmplText))
         template.Must(goFileTmpl.Parse(fieldEncodingTmplText))
 }