Golang protobuf doesn't support custom tags to generated structs. This tool injects custom tags to generated protobuf files, which is commonly used for validating fields, omitting fields from JSON data, etc.
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For OS X:
$ brew install protobuf
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go support for protobuf:
go get -u github.com/golang/protobuf/{proto,protoc-gen-go}
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go install github.com/favadi/protoc-go-inject-tag
or download the binaries from the releases page.
$ protoc-go-inject-tag -h
Usage of protoc-go-inject-tag:
-XXX_skip string
tags that should be skipped (applies 'tag:"-"') for unknown fields (deprecated since protoc-gen-go v1.4.0)
-input string
pattern to match input file(s)
-verbose
verbose logging
-clear_tag_comment
clear tag comment
Add a comment with the following syntax before fields, and these will be
injected into the resulting .pb.go
file. This can be specified above the
field, or trailing the field.
// @gotags: custom_tag:"custom_value"
// file: test.proto
syntax = "proto3";
package pb;
option go_package = "/pb";
message IP {
// @gotags: valid:"ip"
string Address = 1;
// Or:
string MAC = 2; // @gotags: validate:"omitempty"
}
Generate your .pb.go
files with the protoc command as normal:
$ protoc --proto_path=. --go_out=paths=source_relative:. test.proto
Then run protoc-go-inject-tag
against the generated files (e.g test.pb.go
):
$ protoc-go-inject-tag -input=./test.pb.go
# or
$ protoc-go-inject-tag -input="*.pb.go"
The custom tags will be injected to test.pb.go
:
type IP struct {
// @gotags: valid:"ip"
Address string `protobuf:"bytes,1,opt,name=Address,json=address" json:"Address,omitempty" valid:"ip"`
}
To skip the tag for the generated XXX_*
fields (unknown fields), use the
-XXX_skip=yaml,xml
flag. This is deprecated, as this functionality hasn't
existed in protoc-gen-go
since v1.4.x.
Since v1.3.0, we recommend using @gotags:
rather than @inject_tags:
,
as @gotags
is more indicative of the language the comment is for. We don't
plan on removing @inject_tags:
support anytime soon, however we strongly
recommend switching to @gotags
.