[AArnott]

Fixes #3835

SA1009 reports an indented closing parenthesis in a multiline tuple expression even when the opening parenthesis is alone on its line. This makes the reported switch expression layout trigger a false positive.

Allow the exception only when both tuple parentheses are each on their own line. Add the reported switch expression and near-miss cases, and update the SA1009 documentation in all existing locales. The regression test reproduced the SA1009 diagnostic before the analyzer change.

Validation: full SA1009 suites passed on C# 6 (72 tests), C# 9 (97 tests), and C# 15 (105 tests). The one-off probe with all standard and SX analyzers reported no compiler errors or analyzer exceptions for the exact snippet. The snippet does produce unrelated documentation, filename, file-header, and encoding diagnostics in the standalone probe.

Performance: no extra tree walk, allocations, or semantic analysis. The exception is checked only for closing parentheses that start a line; for tuple expressions it checks whether the opening parenthesis is alone on its line.

Behavior change: tuple expressions may have the closing parenthesis indented on its own line when the opening parenthesis is also on its own line.

[Copilot]

🟡 Changes recommended

The exception also permits closing-line expression continuations, exceeding the documented restriction.

1 open issue

• Closing-line exception ignores trailing continuation syntax · New

What changed in this PR

Addresses #3835 by allowing multiline tuple layouts in SA1009, including tuples in switch expressions.

Changes:

• Adds a tuple-specific spacing exception.
• Adds regression and near-miss tests.
• Updates rule documentation in all four locales.

File	Description
test/​StyleCop.Analyzers.Test.CSharp9/​SpacingRules/​SA1009CSharp9UnitTests.cs	Adds the reported switch-expression regression.
test/​StyleCop.Analyzers.Test.CSharp7/​SpacingRules/​SA1009CSharp7UnitTests.cs	Tests allowed tuple layouts and opening-parenthesis near misses.
src/​StyleCop.Analyzers/​SpacingRules/​SA1009ClosingParenthesisMustBeSpacedCorrectly.cs	Adds the tuple spacing exception and updates its documentation.
documentation/​zh-cn/​SA1009.md	Documents the exception in Chinese.
documentation/​SA1009.md	Documents the exception in English.
documentation/​ru-ru/​SA1009.md	Documents the exception in Russian.
documentation/​cs-cz/​SA1009.md	Documents the exception in Czech.

_{Review effort: Balanced}

[Copilot]

🟡 Changes recommended

The closing-line condition still rejects valid standalone parentheses and permits some lines containing additional code.

1 open issue

• Check closing parenthesis line boundaries for SA1009 · New

1 resolved since last review

• Closing-line exception ignores trailing continuation syntax

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

No blocking findings remain, but full CI validation is unconfirmed and requires human verification before approval.

No open issues 🎉

1 resolved since last review

• Check closing parenthesis line boundaries for SA1009

_{Review effort: Balanced}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.62%. Comparing base (2b8bc7d) to head (b226ed2).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4358      +/-   ##
==========================================
- Coverage   97.62%   97.62%   -0.01%     
==========================================
  Files        1336     1338       +2     
  Lines      149792   150250     +458     
  Branches     5098     5125      +27     
==========================================
+ Hits       146239   146676     +437     
- Misses       2265     2272       +7     
- Partials     1288     1302      +14     

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