Auto fill incorrectly detects regex modifier as capture group.

[MichalMKsiazek]

Used Visual Studio

Visual Studio 2026

Are the latest Visual Studio updates installed?

Yes

Content of reqnroll.json (if present)

{
  "$schema": "https://schemas.reqnroll.net/reqnroll-config-latest.json",
  "bindingCulture": {
    "name": "en-GB"
  },
  "ide": {
    "editor": {
      "gherkinFormat": {
        "indentAndSteps": false,
        "indentSteps": true
      }
    }
  }
}

Issue Description

When regex flags/modifiers are use in a step definitions (e.g. (?i)) the auto fill incorrectly detects the flag as a capture group:

[Then(@"(?i)Do not receive mimic messages from DRS until base offset ""(.*)""")]
    public void ThenDoNotReceiveMessagesFromDRSBaseOffset(TimeSpan offset, Table table) { }

The resultant auto fill incorrectly place the TimeSpan and Table vars:

And [TimeSpan]Do not receive mimic messages from DRS until base offset "[Table]"

Note that the the extension does not detect the auto filled expresion as valid

Replacing it with the correct form the regex is detected.

Steps to Reproduce

Use extension version 2026.1.477
Use VS 2026 18.3.2
Create a step definition with regex modifier (?<modifer>) and use auto fill step.

Link to a project repository that reproduces the issue

No response

[clrudolphi]

I think I understand the root cause. In the VS Extension's RegexStepDefinitionExxpressionAnalyzer class there is a utility method

    private bool IsNonCapturingGroup(string regexString, int index) =>
        index + 2 < regexString.Length &&
        regexString[index + 1] == '?' && regexString[index + 2] == ':';

That only recognizes non-capturing groups as those that start (?:
We'll need to enhance that to recognize all the forms of non-capture group syntax.

I suspect there is also an accompanying logic bug in the body of the main method in that class as it assumes that any expression, even non-capture groups, signal the presence of a parameter for the overall binding expression. That won't be true when using syntax such as used in your example.

This class also lacks adequate testing, so we'll need to build those out as well.

[304NotModified]

We'll need to enhance that to recognize all the forms of non-capture group syntax.

Another option is to set the ExpressionType? See https://docs.reqnroll.net/latest/automation/cucumber-expressions.html#explicit-expression-type-control