protocheck

Lightweight solution to ProtocolBuffers message validation. protocheck-proto-gen is a protoc plugin that generates Go code.

features

• expressions with Google/CEL
• both message and field checks
• nested messages
• repeated, oneof and map fields
• syntax validation of CEL expressions at generation time
• supports proto3 and editions

status

Work in progress

install

  go install github.com/emicklei/protocheck/cmd/protocheck-proto-gen@latest

generate

  protoc --go_out=. --go_opt=paths=source_relative --protocheck_out=.

example

package hr;

import "check.proto";

message Person {
  
  // message cross-field checks
  option (check.message) = { 
    cel:"size(this.name + this.surname) > 0" 
    fail:"name and surname cannot be empty" 
    id:"person_invariant" }; // id is optional
  
  // with per field state checks
  string name = 1 [(check.field) = { 
      cel:"size(this.name) > 1"                  
      fail:"name must be longer than 1" }];

  optional string middle_name = 2 [(check.field) = { 
      cel:"size(this.middle_name) > 0"           
      fail:"middle name (if set) cannot be empty" }];

  string surname = 3 [(check.field) = { 
      cel:"size(this.surname) > 1"               
      fail:"surname must be longer than 1" }];

  google.protobuf.Timestamp birth_date  = 4 [(check.field) = { 
      cel:"this.birth_date.getFullYear() > 2000" 
      id:"check_birth_date" }];

See CEL language definition for creating CEL expressions.

getFullYear is one of the supported CEL macros.

usage

p := &Person{
    Name:      "",
    BirthDate: &timestamppb.Timestamp{Seconds:1}
}
err := p.Validate() // a protocheck.ValidationError

considerations

The protocheck package is inspired by bufbuild/protovalidate which also uses the powerful CEL expression language. However, it differs by:

• this always refers to the message
• minimal dependencies (cel and protobuf)
• syntax is more compact