protoc-gen-fieldmask

A protoc plugin that generates fieldmask paths as static type properties for proto messages, which elimantes the usage of error-prone strings.

For example, given the following proto messages:

syntax = "proto3";

package example;

option go_package = "example/;example";

import "google/type/date.proto";

message Foo {
  string baz = 1;
  int32 xyz = 2;
  Bar my_bar = 3;
  google.type.Date some_date = 4;
}

message Bar {
  string some_field = 1;
  bool another_field = 2;
}

fieldmasks paths can be used as follows:

  foo := &example.Foo{}

  // Prints "baz"
  fmt.Println(foo.FieldMaskPaths().Baz())
  
  // Prints "xyz"
  fmt.Println(foo.FieldMaskPaths().Xyz())

  // Prints "my_bar"
  fmt.Println(foo.FieldMaskPaths().MyBar().String())

  // Since baz is a nested message, we can print a nested path - "my_bar.some_field"
  fmt.Println(foo.FieldMaskPaths().MyBar().SomeField())

  // Thirdparty messages work the same way:
  // Prints "some_date"
  fmt.Println(foo.FieldMaskPaths().SomeDate().String())

  // Prints "some_date.year"
  fmt.Println(foo.FieldMaskPaths().SomeDate().Year())

Usage

Installation

The plugin can be downloaded from the release page, and should be ideally installed somewhere available in your $PATH.

Executing the plugin

protoc --fieldmask_out=gen protos/example.proto

# If the plugin is not in your $PATH:
protoc --fieldmask_out=out_dir protos/example.proto --plugin=protoc-gen-fieldmask=/path/to/protoc-gen-fieldmask

Parameters

The following parameters can be set by passing --fieldmask_opt to the command:

• maxdepth: This option is relevant for a recursive message case.
  Specify the max depth for which the paths will be pregenerated. If the path depth gets over the max value, it will be generated at runtime. default value is 7.

Features

• Currently the only supported language is go.
• All paths are pregenerated (except for recursive messages past maxdepth).
• Support all type of fields including repeated fields, maps, oneofs, third parties, nested messages and recursive messages.