Encode and decode fields of union type.

mojom/generators/go/templates/decoding.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 fieldDecodingTmplText = `
 {{- define "FieldDecodingTmpl" -}}
 {{- $info := . -}}
 {{- if $info.IsPointer -}}
 pointer, err := decoder.ReadPointer()
 if err != nil {
         return err
 }
 if pointer == 0 {
-{{- if $info.IsNullable }}
+{{- if $info.IsNullable}}
         {{$info.Identifier}} = nil
-{{- else }}
+{{- else if $info.IsUnion}}
+        return &bindings.ValidationError{bindings.UnexpectedNullPointer, "unexpected null union pointer"}
+{{- else}}
         return &bindings.ValidationError{bindings.UnexpectedNullPointer, "unexpected null pointer"}
 {{- end }}
 } else {
         {{ template "NonNullableFieldDecodingTmpl" $info }}
 }
 {{- else -}}
 {{ template "NonNullableFieldDecodingTmpl" $info }}
 {{- end -}}
 {{- end -}}
 `
@@ skipping 23 matching lines @@
         return &bindings.ValidationError{bindings.UnexpectedInvalidHandle, "unexpected invalid handle"}
 {{- end -}}
 }
 {{- else if $info.IsStruct -}}
 {{- if $info.IsNullable -}}
 {{$info.Identifier}} = new({{$info.GoType}})
 {{end -}}
 if err := {{$info.Identifier}}.Decode(decoder); err != nil {
         return err
 }
+{{- else if $info.IsUnion -}}
+{{- if $info.IsPointer -}}
+if err := decoder.StartNestedUnion(); err != nil {
+        return err
+}
+{{end -}}
+var err error
+{{$info.Identifier}}, err = Decode{{$info.GoType}}(decoder)
+if err != nil {
+        return err
+}
+{{- if not $info.IsNullable}}
+if {{$info.Identifier}} == nil {
+        return &bindings.ValidationError{bindings.UnexpectedNullUnion, "unexpected null union"}
+}
+{{- end -}}
+{{- if $info.IsPointer}}
+decoder.Finish()
+{{- end -}}
 {{- else if $info.IsArray -}}
 {{ $elInfo := $info.ElementEncodingInfo -}}
 len0, err := decoder.StartArray({{$elInfo.BitSize}})
 if err != nil {
         return err
 }
 {{$info.Identifier}} = make({{$info.GoType}}, len0)
 for i := uint32(0); i < len0; i++ {
         {{ template "FieldDecodingTmpl" $elInfo }}
         {{$info.Identifier}}[i] = {{$elInfo.Identifier}}
@@ skipping 30 matching lines @@
         (*{{$info.Identifier}})[{{$keyInfo.Identifier}}[i]] = {{$valueInfo.Identifier}}[i]
 }
 {{- end -}}
 {{- end -}}
 `
 
 func initDecodingTemplates() {
         template.Must(goFileTmpl.Parse(nonNullableFieldDecodingTmplText))
         template.Must(goFileTmpl.Parse(fieldDecodingTmplText))
 }