Fix property pattern indentation in positional and parenthesized patterns

[Copilot]

Fix Property Pattern Indentation in Positional and Parenthesized Patterns ✅

Problem

• Add test case to reproduce the issue in FormattingTests_Patterns.cs
• Identify root cause in IndentBlockFormattingRule.cs
• Fix the indentation calculation for PropertyPatternClause inside SubpatternSyntax
• Run broader formatting tests to ensure no regressions
• Run code review and security scanning
• Update WorkItem reference to correct issue number (Bad formatting on property pattern in a positional pattern when line wrapping #54434)
• Add test for parenthesized patterns (single pattern without comma separation)

Summary

Fixed issue #54434 where property patterns inside positional (tuple) patterns were being incorrectly dedented during formatting. The fix also handles parenthesized patterns without comma separation.

Before: Property patterns in tuple patterns would dedent by 2 levels instead of maintaining proper indentation.
After: Property patterns are correctly indented with one additional level relative to the containing pattern.

Root Cause

When a RecursivePatternSyntax was inside a SubpatternSyntax (positional pattern context), the code attempted to use recursivePatternParent.GetFirstToken() as the alignment base. However, since the RecursivePattern could start with the property pattern's opening brace itself, this resulted in baseTokenForAlignment == propertyPatternClause.OpenBraceToken, causing the alignment operation to be skipped entirely. This led to incorrect dedentation as fallback rules took over.

Solution

Modified IndentBlockFormattingRule.AddAlignmentBlockOperation for the PropertyPatternClauseSyntax case to:

1. Detect when a RecursivePattern is inside a SubpatternSyntax (positional pattern context)
2. Navigate up the syntax tree: SubpatternSyntax → PositionalPatternClauseSyntax → outer RecursivePatternSyntax → use its parent as the alignment base
3. Use FormattingOperations.CreateRelativeIndentBlockOperation directly with indentationDelta = 1 to add one indentation level
4. Remove the IndentIfConditionOfAnchorToken flag for positional patterns (only applies to regular is patterns)

Testing Results

✅ New test FormatPropertyPatternInPositionalPattern1 passes (tuple patterns with comma separation)
✅ New test FormatPropertyPatternInParenthesizedPattern1 passes (parenthesized patterns without comma separation)
✅ All 56 pattern formatting tests pass
✅ All 597 formatting tests pass (1 skipped)
✅ CodeQL security scan: No issues found

Security Summary

No security vulnerabilities were introduced or fixed by this change.

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[CyrusNajmabadi]

@copilot update tehse workitems to #54434

[Copilot]

Updated WorkItem reference to #54434 in commit 2dc9d9a.

[CyrusNajmabadi]

@copilot test parenthesized patterns as well. so just (...) without comma separation.

[Copilot]

Added test FormatPropertyPatternInParenthesizedPattern1 for parenthesized patterns without comma separation in commit f31e665.

[CyrusNajmabadi]

@dotnet/roslyn-ide ptal.

[JoeRobich]

This test code doesn't exactly match the case from the issue. Should we add a test where (former, latter) is not ( is on a new line?

[CyrusNajmabadi]

sure. i can add in followup!

[akhera99]

confusing that the expected comes before the original

[CyrusNajmabadi]

yes. i highly dislike formatter tests for this reason :'(

[JoeRobich]

Can copilot add named arguments and reverse the order? =)