go-proto-validators

Open source

Generate message validators from .proto annotations.

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About

Generate message validators from .proto annotations.

Golang ProtoBuf Validator Compiler

A protoc plugin that generates Validate() error functions on Go proto structs based on field options inside .proto files. The validation functions are code-generated and thus don't suffer on performance from tag-based reflection on deeply-nested messages.

Requirements

Using Protobuf validators is currently verified to work with:

Go 1.11, 1.12, 1.13
Protobuf @ v3.8.0
Go Protobuf @ v1.3.2
Gogo Protobuf @ v1.3.0

It should still be possible to use it in project using earlier Go versions. However if you want to contribute to this repository you'll need at least 1.11 for Go module support.

Paint me a code picture

Let's take the following proto3 snippet:

…

First, the required keyword is back for proto3, under the guise of msg_exists. The painful if-nil checks are taken care of!

Second, the expected values in fields are now part of the contract .proto file. No more hunting down conditions in code!

Third, the generated code is understandable and has clear understandable error messages. Take a look:

…

Installing and using

The protoc compiler expects to find plugins named proto-gen-XYZ on the execution $PATH. So first:

bash

export PATH=${PATH}:${GOPATH}/bin

Then, do the usual

bash

go get github.com/mwitkow/go-proto-validators/protoc-gen-govalidators

Your protoc builds probably look very simple like:

bash

protoc  \
  --proto_path=. \
  --go_out=. \
  *.proto

That's fine, until you encounter .proto includes. Because go-proto-validators uses field options inside the .proto files themselves, it's .proto definition (and the Google descriptor.proto itself) need to on the protoc include path. Hence the above becomes:

bash

protoc  \
  --proto_path=${GOPATH}/src \
  --proto_path=${GOPATH}/src/github.com/google/protobuf/src \
  --proto_path=. \
  --go_out=. \
  --govalidators_out=. \
  *.proto

Or with gogo protobufs:

bash

protoc  \
  --proto_path=${GOPATH}/src \
  --proto_path=${GOPATH}/src/github.com/gogo/protobuf/protobuf \
  --proto_path=. \
  --gogo_out=. \
  --govalidators_out=gogoimport=true:. \
  *.proto

Basically the magical incantation (apart from includes) is the --govalidators_out. That triggers the protoc-gen-govalidators plugin to generate mymessage.validator.pb.go. That's it :)