Empty String Effect (vscode editor render effect; parsed result is ok)

[goto40]

I have a (probably stupid) question but I did not find a solution in the discussions (I use langium 0.4.0)...

I have a grammar which allows string inputs:

terminal STRING returns string: /("([^"])*")|('([^'])*')/;

But somehow, the vscode editor interprets empty string as the start of a multiline string(?):

Is there a solution to that problem?

[msujew]

Hey @goto40,

that's probably due to the textMate syntax that we generate. The heuristic that we use probably has generated something unsensible in your case. Can you shared what your tmLanguage.json file contains?

Also, I believe that terminal STRING returns string: /"[^"]*"|'[^']*'/; (the same as your terminal, just without the ()) works as expected and actually parses the same way.

[goto40]

Here is the *.tmLanguage.json:

• Probably the the "end": "[^']'" is not ok - it does not allow an empty string...?
• Is this file generated? - I did not edit it.

{
  "name": "message-dsl",
  "scopeName": "source.message-dsl",
  "fileTypes": [
    ".msg",
    ".item"
  ],
  "patterns": [
    {
      "include": "#comments"
    },
    {
      "name": "keyword.control.message-dsl",
      "match": "\\b(applicable|applicable_for|array|by|constant|constants|description|embedded|enum|enum_value|extends|for|if|import|message|optional|package|per|property|property_set|rawtype|scalar|struct|struct_definition|times|times_per_message|to|value|variant)\\b"
    },
    {
      "name": "string.quoted.double.message-dsl",
      "begin": "\"",
      "end": "[^\"]\""
    },
    {
      "name": "string.quoted.single.message-dsl",
      "begin": "'",
      "end": "[^']'"
    }
  ],
  "repository": {
    "comments": {
      "patterns": [
        {
          "name": "comment.block.message-dsl",
          "begin": "/\\*",
          "beginCaptures": {
            "0": {
              "name": "punctuation.definition.comment.message-dsl"
            }
          },
          "end": "\\*/",
          "endCaptures": {
            "0": {
              "name": "punctuation.definition.comment.message-dsl"
            }
          }
        },
        {
          "begin": "//",
          "beginCaptures": {
            "1": {
              "name": "punctuation.whitespace.comment.leading.message-dsl"
            }
          },
          "end": "(?=$)",
          "name": "comment.line.message-dsl"
        }
      ]
    }
  }
}

P.S. You are right, the parentheses are not necessary.

[msujew]

Yes the file is generated. The CLI tries to guess what certain terminals mean, how they start and end, and generates the .tmLanguage.json based off of that. The file is responsible for syntactic highlighting in vscode.

I believe you can probably strip even more parenthesis, just use /"[^"]*"|'[^']*'/. This definitely generates correctly.

[goto40]

Thank you, @msujew.
Great hint! Works.