protoc-gen-cue

This protoc plugin generates CUE files.

Conversions

Complies with protojson.

Basic Types

Proto Type	CUE Type	Comments
map<K, V>	{ [string]: V }	All keys are converted to strings.
repeated V	[...V]
bool	bool	Use default option for defaults.
string	string	Use default option for defaults.
bytes	bytes	Use default option for defaults.
int32	int32	Use default option for defaults.
fixed32	int32	Use default option for defaults.
uint32	uint32	Use default option for defaults.
int64	int64	Use default option for defaults.
fixed64	int64	Use default option for defaults.
uint64	uint64	Use default option for defaults.
float	float32	Use default option for defaults.
double	float64	Use default option for defaults.
Any	*null | { "@type": string, ... }
Struct	*null | { [string]: _ }
Value	*null | _
ListValue	*null | [...]
NullValue	*null | null
BoolValue	*null | bool
StringValue	*null | string
Int32Value	*null | int32
UInt32Value	*null | uint32
Int64Value	*null | int64
UInt64Value	*null | uint64
FloatValue	*null | float32
DoubleValue	*null | double
Empty	*null | close({})
Timestamp	*null | string	See the Timestamp section for more information.
Duration	*null | string	See the Duration section for more information.
FieldMask	*null | string

Message

import "github.com/ornew/protoc-gen-cue/pkg/options/cue.proto";

message Foo {
  string name = 1 [(cue.field).expr = '!="xxx"'];
  int32 age = 2 [(cue.field).expr = '<100'];
  int32 age_next_year = 3 [(cue.field).expr = 'age+1'];
}

To:

#Foo: {
  name: string
  name: !="xxx"
  age: int32
  age: <100
  ageNextYear: int32
  ageNextYear: age+1
}

Default Values

You can specify default values using the default field option:

message User {
  bool active = 1 [(cue.field).default = "*true"];
  int32 age = 2 [(cue.field).default = "*18"];
  string role = 3 [(cue.field).default = "*\"user\""];
}

To:

#User: {
  active: *true | bool
  age: *18 | int32
  role: *"user" | string
}

Custom CUE Package

You can specify a custom CUE import path for your proto files:

option (cue.cue_package) = "example.com/schemas/v1";

This allows you to control the CUE import path independently from the Go package path.

Enum

enum Bar {
  ZERO = 0;
  ONE = 1;
}

To:

#Bar: *#Bar_ZERO | #Bar_ONE

#Bar_ZERO: "ZERO"
#Bar_ONE:  "ONE"

Oneof

message Car {
  oneof id {
    string product_name = 1;
    int32 serial_number = 2;
  }
}

To:

#Car: {
  _oneof_id: productName & serialNumber
  productName?: string
  serialNumber?: int32
}

Timestamp

Currently defined by an unconstrained string. This is due to the fact that CUE's built-in time.Time constraint is incompatible with the JSON format defined in the timestamppb. We plan to fix this issue in a future version to follow the original format. See for more details: time.Time on pkg.go.dev and timestamppb.Timestamp

Duration

Currently defined by an unconstrained string. This is due to the fact that CUE's built-in time.Duration constraint is incompatible with the JSON format defined in the durationpb. We plan to fix this issue in a future version to follow the original format. See for more details: time.Duration in pkg.go.dev and descriptorpb.Duration

Optional (proto3)

message Dog {
  optional string nick_name = 1;
}

To:

#Dog: {
  nickName?: string
}