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// Copyright 2019 CUE Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package protobuf
import (
func protoToCUE(typ string, options []*proto.Option) ast.Expr {
t, ok := scalars[typ]
if !ok {
return nil
return predeclared(t)
var scalars = map[string]string{
// Differing
"sint32": "int32",
"sint64": "int64",
"fixed32": "uint32",
"fixed64": "uint64",
"sfixed32": "int32",
"sfixed64": "int64",
// Identical to CUE
"int32": "int32",
"int64": "int64",
"uint32": "uint32",
"uint64": "uint64",
"double": "float64",
"float": "float32",
"bool": "bool",
"string": "string",
"bytes": "bytes",
func predeclared(s string) ast.Expr {
return &ast.Ident{
Name: s,
Node: ast.NewIdent("__" + s),
func (p *protoConverter) setBuiltin(from string, to func() ast.Expr, pkg *protoConverter) {
p.scope[0][from] = mapping{to, pkg}
func (p *protoConverter) setBuiltinParse(from, to string, pkg *protoConverter) {
f := func() ast.Expr {
expr, err := parser.ParseExpr("", to, parser.ParseComments)
if err != nil {
panic(fmt.Sprintf("error parsing name %q: %v", to, err))
return expr
p.scope[0][from] = mapping{f, pkg}
var (
pkgTime = &protoConverter{cuePkgPath: "time"}
pkgStruct = &protoConverter{cuePkgPath: "struct"}
importTime = ast.NewImport(nil, "time")
importStruct = ast.NewImport(nil, "struct")
func (p *protoConverter) mapBuiltinPackage(pos scanner.Position, file string, required bool) (generate bool) {
// Map some builtin types to their JSON/CUE mappings.
switch file {
case "gogoproto/gogo.proto":
case "google/protobuf/struct.proto":
p.setBuiltin("google.protobuf.Struct", func() ast.Expr {
return ast.NewStruct()
}, nil)
p.setBuiltin("google.protobuf.Value", func() ast.Expr {
return ast.NewIdent("_")
}, nil)
p.setBuiltin("google.protobuf.NullValue", func() ast.Expr {
return ast.NewNull()
}, nil)
p.setBuiltin("google.protobuf.ListValue", func() ast.Expr {
return ast.NewList(&ast.Ellipsis{})
}, nil)
p.setBuiltin("google.protobuf.StringValue", func() ast.Expr {
return predeclared("string")
}, nil)
p.setBuiltin("google.protobuf.BoolValue", func() ast.Expr {
return predeclared("bool")
}, nil)
p.setBuiltin("google.protobuf.NumberValue", func() ast.Expr {
return predeclared("number")
}, nil)
return false
case "google/protobuf/empty.proto":
f := func() ast.Expr {
time := &ast.Ident{Name: "struct", Node: importStruct}
return ast.NewCall(
ast.NewSel(time, "MaxFields"),
ast.NewLit(token.INT, "0"),
p.setBuiltin("google.protobuf.Empty", f, pkgStruct)
return false
case "google/protobuf/duration.proto":
f := func() ast.Expr {
time := &ast.Ident{Name: "time", Node: importTime}
return ast.NewSel(time, "Duration")
p.setBuiltin("google.protobuf.Duration", f, pkgTime)
return false
case "google/protobuf/timestamp.proto":
f := func() ast.Expr {
time := &ast.Ident{Name: "time", Node: importTime}
return ast.NewSel(time, "Time")
p.setBuiltin("google.protobuf.Timestamp", f, pkgTime)
return false
case "google/protobuf/any.proto":
// TODO: technically, the value should be `_` (anything), but that
// will not convert to a valid OpenAPI value. In practice, all
// "well-known" types except wrapper types (which will likely not
// be used here) are represented as strings.
// In Structural OpenAPI this type cannot be represented.
p.setBuiltinParse("google.protobuf.Any", `{
// A URL/resource name that uniquely identifies the type of the serialized protocol buffer message. This string must contain at least one "/" character. The last segment of the URL's path must represent the fully qualified name of the type (as in `+
"``"+`). The name should be in a canonical form (e.g., leading "." is not accepted).
// The remaining fields of this object correspond to fields of the proto messsage. If the embedded message is well-known and has a custom JSON representation, that representation is assigned to the 'value' field.
"@type": string,
}`, nil)
return false
case "google/protobuf/wrappers.proto":
p.setBuiltinParse("google.protobuf.DoubleValue", `null | float`, nil)
p.setBuiltinParse("google.protobuf.FloatValue", `null | float`, nil)
p.setBuiltinParse("google.protobuf.Int64Value", `null | int64`, nil)
p.setBuiltinParse("google.protobuf.UInt64Value", `null | uint64`, nil)
p.setBuiltinParse("google.protobuf.Int32Value", `null | int32`, nil)
p.setBuiltinParse("google.protobuf.UInt32Value", `null | uint32`, nil)
p.setBuiltinParse("google.protobuf.BoolValue", `null | bool`, nil)
p.setBuiltinParse("google.protobuf.StringValue", `null | string`, nil)
p.setBuiltinParse("google.protobuf.BytesValue", `null | bytes`, nil)
return false
// case "google/protobuf/field_mask.proto":
// p.setBuiltin("google.protobuf.FieldMask", "protobuf.FieldMask", nil)
// protobuf.Any
if required {
failf(pos, "import %q not found", file)
return true