Constant does not support MessageValue

[alex-ac]

The language spec: https://protobuf.dev/reference/protobuf/edition-2023-spec/#constant

States the following:

Constant

constant = fullIdent | ( [ "-" | "+" ] intLit ) | ( [ "-" | "+" ] floatLit ) |
                strLit | boolLit | MessageValue

MessageValue is defined in the Text Format Language Specification.

However, at the moment Lexer does not MessageValue when reading constants: https://github.com/yoheimuta/go-protoparser/blob/master/lexer/constant.go#L11

Without this support it's impossible to parse all possible values for options. Example from the impleminting editions support page:

edition = "2023";

package foo;

import "google/protobuf/descriptor.proto";

extend google.protobuf.FeatureSet {
  MyFeatures features = <extension #>;
}

message MyFeatures {
  enum FeatureValue {
    FEATURE_VALUE_UNKNOWN = 0;
    VALUE1 = 1;
    VALUE2 = 2;
  }

  FeatureValue feature_value = 1 [
    targets = TARGET_TYPE_FIELD,
    targets = TARGET_TYPE_FILE,
    feature_support = {
      edition_introduced: EDITION_2023,
      edition_deprecated: EDITION_2024,
      deprecation_warning: "Feature will be removed in 2025",
      edition_removed: EDITION_2025,
    },
    edition_defaults = { edition: EDITION_LEGACY, value: "VALUE1" },
    edition_defaults = { edition: EDITION_2024, value: "VALUE2" }
  ];
}

However, this issue is not limited to editions, because any custom option which value type is a message, will be impossible to parse.

I understand, it's quite a complex thing to support, because it pulls in complete support of protobuf text format language. It also possible that parsing message values properly will introduce the backward-incompatibility in *Option types.

[yoheimuta]

Without this support it's impossible to parse all possible values for options. Example from the impleminting editions support page:

Can you give me the specific error message?
I couldn't reproduce it.

diff --git a/_example/dump/main.go b/_example/dump/main.go
index 59ae9a4..edbd5a4 100644
--- a/_example/dump/main.go
+++ b/_example/dump/main.go
@@ -12,7 +12,7 @@ import (
 )

 var (
-       proto      = flag.String("proto", "_testdata/simple.proto", "path to the Protocol Buffer file")
+       proto      = flag.String("proto", "_testdata/messageValue.proto", "path to the Protocol Buffer file")
        debug      = flag.Bool("debug", false, "debug flag to output more parsing process detail")
        permissive = flag.Bool("permissive", true, "permissive flag to allow the permissive parsing rather than the just documented spec")
        unordered  = flag.Bool("unordered", false, "unordered flag to output another one without interface{}")

11:51:56 ~/yoheimuta/go-protoparser $ cat _testdata/messageValue.proto                                                                                     git/master
edition = "2023";

package foo;

import "google/protobuf/descriptor.proto";

message MyFeatures {
  enum FeatureValue {
    FEATURE_VALUE_UNKNOWN = 0;
    VALUE1 = 1;
    VALUE2 = 2;
  }

  FeatureValue feature_value = 1 [
    targets = TARGET_TYPE_FIELD,
    targets = TARGET_TYPE_FILE,
    feature_support = {
      edition_introduced: EDITION_2023,
      edition_deprecated: EDITION_2024,
      deprecation_warning: "Feature will be removed in 2025",
      edition_removed: EDITION_2025,
    },
    edition_defaults = { edition: EDITION_LEGACY, value: "VALUE1" },
    edition_defaults = { edition: EDITION_2024, value: "VALUE2" }
  ];
}

11:46:59 ~/yoheimuta/go-protoparser $ make run/dump/example                                                                                                git/master
go run _example/dump/main.go -debug=false -permissive=true -unordered=false
{
  "Syntax": null,
  "Edition": {
    "Edition": "2023",
    "EditionQuote": "\"2023\"",
    "Comments": null,
    "InlineComment": null,
    "Meta": {
      "Pos": {
        "Filename": "messageValue.proto",
        "Offset": 0,
        "Line": 1,
        "Column": 1
      },
      "LastPos": {
        "Filename": "messageValue.proto",
        "Offset": 16,
        "Line": 1,
        "Column": 17
      }
    }
  },
  "ProtoBody": [
    {
      "Name": "foo",
      "Comments": null,
      "InlineComment": null,
      "Meta": {
        "Pos": {
          "Filename": "messageValue.proto",
          "Offset": 19,
          "Line": 3,
          "Column": 1
        },
        "LastPos": {
          "Filename": "messageValue.proto",
          "Offset": 30,
          "Line": 3,
          "Column": 12
        }
      }
    },
    {
      "Modifier": 0,
      "Location": "\"google/protobuf/descriptor.proto\"",
      "Comments": null,
      "InlineComment": null,
      "Meta": {
        "Pos": {
          "Filename": "messageValue.proto",
          "Offset": 33,
          "Line": 5,
          "Column": 1
        },
        "LastPos": {
          "Filename": "messageValue.proto",
          "Offset": 74,
          "Line": 5,
          "Column": 42
        }
      }
    },
    {
      "MessageName": "MyFeatures",
      "MessageBody": [
        {
          "EnumName": "FeatureValue",
          "EnumBody": [
            {
              "Ident": "FEATURE_VALUE_UNKNOWN",
              "Number": "0",
              "EnumValueOptions": null,
              "Comments": null,
              "InlineComment": null,
              "Meta": {
                "Pos": {
                  "Filename": "messageValue.proto",
                  "Offset": 124,
                  "Line": 9,
                  "Column": 5
                },
                "LastPos": {
                  "Filename": "messageValue.proto",
                  "Offset": 149,
                  "Line": 9,
                  "Column": 30
                }
              }
            },
            {
              "Ident": "VALUE1",
              "Number": "1",
              "EnumValueOptions": null,
              "Comments": null,
              "InlineComment": null,
              "Meta": {
                "Pos": {
                  "Filename": "messageValue.proto",
                  "Offset": 155,
                  "Line": 10,
                  "Column": 5
                },
                "LastPos": {
                  "Filename": "messageValue.proto",
                  "Offset": 165,
                  "Line": 10,
                  "Column": 15
                }
              }
            },
            {
              "Ident": "VALUE2",
              "Number": "2",
              "EnumValueOptions": null,
              "Comments": null,
              "InlineComment": null,
              "Meta": {
                "Pos": {
                  "Filename": "messageValue.proto",
                  "Offset": 171,
                  "Line": 11,
                  "Column": 5
                },
                "LastPos": {
                  "Filename": "messageValue.proto",
                  "Offset": 181,
                  "Line": 11,
                  "Column": 15
                }
              }
            }
          ],
          "Comments": null,
          "InlineComment": null,
          "InlineCommentBehindLeftCurly": null,
          "Meta": {
            "Pos": {
              "Filename": "messageValue.proto",
              "Offset": 100,
              "Line": 8,
              "Column": 3
            },
            "LastPos": {
              "Filename": "messageValue.proto",
              "Offset": 185,
              "Line": 12,
              "Column": 3
            }
          }
        },
        {
          "IsRepeated": false,
          "IsRequired": false,
          "IsOptional": false,
          "Type": "FeatureValue",
          "FieldName": "feature_value",
          "FieldNumber": "1",
          "FieldOptions": [
            {
              "OptionName": "targets",
              "Constant": "TARGET_TYPE_FIELD"
            },
            {
              "OptionName": "targets",
              "Constant": "TARGET_TYPE_FILE"
            },
            {
              "OptionName": "feature_support",
              "Constant": "{edition_introduced:EDITION_2023,edition_deprecated:EDITION_2024,deprecation_warning:\"Feature will be removed in 2025\",edition_removed:EDITION_2025,}"
            },
            {
              "OptionName": "edition_defaults",
              "Constant": "{edition:EDITION_LEGACY,value:\"VALUE1\"}"
            },
            {
              "OptionName": "edition_defaults",
              "Constant": "{edition:EDITION_2024,value:\"VALUE2\"}"
            }
          ],
          "Comments": null,
          "InlineComment": null,
          "Meta": {
            "Pos": {
              "Filename": "messageValue.proto",
              "Offset": 190,
              "Line": 14,
              "Column": 3
            },
            "LastPos": {
              "Filename": "messageValue.proto",
              "Offset": 636,
              "Line": 25,
              "Column": 4
            }
          }
        }
      ],
      "Comments": null,
      "InlineComment": null,
      "InlineCommentBehindLeftCurly": null,
      "Meta": {
        "Pos": {
          "Filename": "messageValue.proto",
          "Offset": 77,
          "Line": 7,
          "Column": 1
        },
        "LastPos": {
          "Filename": "messageValue.proto",
          "Offset": 638,
          "Line": 26,
          "Column": 1
        }
      }
    }
  ],
  "Meta": {
    "Filename": "messageValue.proto"
  }
}