Support nested annotation syntax

Describe the bug I am using https://github.com/envoyproxy/protoc-gen-validate to generate validators for my protobuf using annotations.

Both of the following are valid syntax and compiles properly, but is considered to be invalid by the protobuf plugin:

Formatted by https://github.com/uber/prototool

message SomeMessage {
  repeated string ids = 1 [
    (validate.rules).repeated = {
      items: {
        string: {
          len: 36
        }
      }
      min_items: 1
    }
  ];
}

In a single line:

message SomeMessage {
  repeated string ids = 1 [(validate.rules).repeated = {items {string {len: 36}}, min_items: 1}];
}

To Reproduce Steps to reproduce the behavior:

1. Paste the above snippets into the editor and see errors being highlighted.

Expected behavior The above snippets are valid and should not be considered errors

Screenshots

Plugin (please complete the following information):

• OS: Windows 10 May Update
• Plugin version: v0.13.0
• IDE: GoLand 2019.1.3

[jvolkman]

Shameless plug for anyone that needs to use the types of long-form options described in this issue: https://plugins.jetbrains.com/plugin/14004

[jvolkman]

You mean that text format is fully supported to express option values in the language? When I said support was partial, I meant the support of text format in the protostuff compiler that is used by this plugin.

Yeah. This part of the proto language isn’t well-specified, but protoc just defers to the text format parser for these long form options (relevant code in descriptor.cc).