lang/go: Add Context.FieldType{PackageName,ImportPath}

lang/go/context.go

@@ -60,6 +60,16 @@ type Context interface {
 
 	// OutputPath returns the output path relative to the plugin's output destination
 	OutputPath(entity pgs.Entity) pgs.FilePath
+
+	// FieldTypeImportPath returns name of the Field type's package as it would appear in
+	// Go source generated by the official protoc-gen-go plugin.
+	// For builtin types empty Name will be returned.
+	FieldTypePackageName(field pgs.Field) pgs.Name
+
+	// FieldTypeImportPath returns the Go import path of the type of the Field
+	// as it would be included in an import block in a Go file.
+	// For builtin types empty FilePath will be returned.
+	FieldTypeImportPath(field pgs.Field) pgs.FilePath
 }
 
 type context struct{ p pgs.Parameters }

lang/go/package.go

@@ -40,12 +40,45 @@ func (c context) PackageName(node pgs.Node) pgs.Name {
 	return pgs.Name(pkg)
 }
 
+func fieldEntity(f pgs.Field) (pgs.Entity, bool) {
+	switch ft := f.Type(); {
+	case ft.IsEmbed():
+		return ft.Embed(), true
+	case ft.IsEnum():
+		return ft.Enum(), true
+	case ft.IsRepeated(), ft.IsMap():
+		switch el := ft.Element(); {
+		case el.IsEmbed():
+			return el.Embed(), true
+		case el.IsEnum():
+			return el.Enum(), true
+		}
+	}
+	return nil, false
+}
+
+func (c context) FieldTypePackageName(f pgs.Field) pgs.Name {
+	en, ok := fieldEntity(f)
+	if !ok {
+		return pgs.Name("")
+	}
+	return c.PackageName(en)
+}
+
 func (c context) ImportPath(e pgs.Entity) pgs.FilePath {
 	path, _ := c.optionPackage(e)
 	path = c.p.Str("import_prefix") + path
 	return pgs.FilePath(path)
 }
 
+func (c context) FieldTypeImportPath(f pgs.Field) pgs.FilePath {
+	en, ok := fieldEntity(f)
+	if !ok {
+		return pgs.FilePath("")
+	}
+	return c.ImportPath(en)
+}
+
 func (c context) OutputPath(e pgs.Entity) pgs.FilePath {
 	out := e.File().InputPath().SetExt(".pb.go")