[AArnott]

Multiline C# 12 collection expressions could leave the closing bracket beside the last element, even after adding a trailing comma. SA1500 did not inspect collection expressions, and SA1137 skipped closing-bracket alignment when the opening bracket followed an assignment or other code.

Changes

• Extend SA1500 to require the first element to start after the opening bracket's line and the closing bracket to start on its own line. Keep opening brackets after assignments or other code valid.
• Extend the SA1500 code fix to preserve comments and handle nested collections and Fix All.
• Make SA1137 align a standalone closing bracket with the indentation of the opening bracket's line, rather than its column after preceding code.
• Update English, Czech, Russian, and Simplified Chinese rule documentation.

Behavior change: Multiline collection expressions now produce SA1500 diagnostics for shared element/bracket lines, and SA1137 diagnostics for misaligned closing brackets after inline opening brackets. Single-line collections remain valid. SA1413 and its code fix are unchanged in this PR.

Validation

Regression tests first reproduced the missing SA1500 diagnostics and the missing SA1137 diagnostic for inline opening brackets before the corresponding analyzer changes. The reported opening-bracket/first-element layout already triggered SA1137 for its misaligned closing bracket; a regression preserves that behavior.

• Debug build of the C# 15 test project and its dependencies: zero warnings and errors.
• Complete SA1500 and SA1137 suites passed in the base and C# 12, 13, 14, and 15 projects.
• Coverage includes nested Fix All, optional trailing commas, comments, spread elements, tabs, LF/CRLF, and valid layouts.
• Targeted documentation-source localization checks passed. The full documentation suite requires generated site/status artifacts not present locally.

Performance

SA1500 adds a narrowly registered collection-expression callback using syntax/token line checks only. SA1137's additional source-text indentation scan is limited to multiline collection expressions with inline opening brackets and standalone closing brackets. No semantic-model calls or whole-tree walks are added; code without collection expressions retains its existing analysis path. Performance was not benchmarked.

[Copilot]

🟡 Changes recommended

The code fix can introduce SA1137 by indenting a nested collection’s opening bracket without adjusting its matching closing bracket, requiring an indentation fix and regression coverage.

1 open issue

• Adjust nested closing bracket indentation when fixing SA1500 · New

What changed in this PR

This PR extends StyleCop’s SA1500 and SA1137 rules to handle multiline C# 12 collection-expression brackets while preserving valid inline opening brackets and single-line collections.

Changes:

• Add collection-expression layout checks and extend the SA1500 code fix.
• Align standalone closing brackets with the opening line’s indentation, with regression coverage for layout and trivia handling.
• Update both rules’ documentation in English, Czech, Russian, and Simplified Chinese.

File	Description
test/​StyleCop.Analyzers.Test.CSharp12/​ReadabilityRules/​SA1137CSharp12UnitTests.cs	Tests inline-opening bracket alignment and valid layouts.
test/​StyleCop.Analyzers.Test.CSharp12/​LayoutRules/​SA1500CSharp12UnitTests.cs	Adds collection layout, comment preservation, and nested Fix All tests.
src/​StyleCop.Analyzers/​ReadabilityRules/​SA1137ElementsShouldHaveTheSameIndentation.cs	Checks closing-bracket indentation after inline openings.
src/​StyleCop.Analyzers/​LayoutRules/​SA1500BracesForMultiLineStatementsMustNotShareLine.cs	Adds multiline collection-expression bracket checks.
src/​StyleCop.Analyzers.CodeFixes/​LayoutRules/​SA1500CodeFixProvider.cs	Extends bracket placement and nested indentation fixes.
documentation/​zh-cn/​SA1500.md	Documents collection layout in Simplified Chinese.
documentation/​zh-cn/​SA1137.md	Documents bracket alignment in Simplified Chinese.
documentation/​SA1500.md	Explains collection-expression layout requirements.
documentation/​SA1137.md	Explains collection bracket and element indentation.
documentation/​ru-ru/​SA1500.md	Documents collection layout in Russian.
documentation/​ru-ru/​SA1137.md	Documents bracket alignment in Russian.
documentation/​cs-cz/​SA1500.md	Documents collection layout in Czech.
documentation/​cs-cz/​SA1137.md	Documents bracket alignment in Czech.

_{Review effort: Balanced}

[codecov]

Codecov Report

❌ Patch coverage is 98.99749% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.64%. Comparing base (d4fdfe5) to head (4bff882).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #4396    +/-   ##
========================================
  Coverage   97.64%   97.64%            
========================================
  Files        1349     1350     +1     
  Lines      153329   153725   +396     
  Branches     5272     5286    +14     
========================================
+ Hits       149719   150110   +391     
  Misses       2280     2280            
- Partials     1330     1335     +5     

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[Copilot]

🔵 Needs a closer look

The code fix can introduce SA1137 by leaving closing brackets misaligned when moving mixed initializer/collection expressions or nested cast/parenthesized collections, affecting both single fixes and Fix All.

No open issues 🎉

2 previously missed issues

In code that hasn't changed since last review

Realign closing brackets inside moved cast expressions

src/​StyleCop.Analyzers.CodeFixes/​LayoutRules/​SA1500CodeFixProvider.cs:156

For int[][] values = [(int[])[ with the element and both closing brackets on later lines, and both brackets aligned at four spaces, fixing the outer [ moves (int[])[ to eight spaces but leaves the inner ] at four. Both the single fix and Fix All introduce SA1137 because this adjustment only handles an immediately following [, not a collection inside the moved cast or parenthesized expression. Realign matching closing brackets for those moved collection openings, and add cast/parenthesized regressions.

Fix All misaligns closing bracket after initializer moves

src/​StyleCop.Analyzers.CodeFixes/​LayoutRules/​SA1500CodeFixProvider.cs:264

For int[][] values = new int[][] {[ with 1], on the next line and }; below it, Fix All moves [ one indentation level inward but leaves the separately fixed ] at the original indentation, introducing SA1137. The closing-bracket calculation accounts for a preceding [ but not the initializer { being fixed. Account for the initializer's movement when calculating bracket indentation, and add a mixed initializer/collection Fix All regression.

1 resolved since last review

• Adjust nested closing bracket indentation when fixing SA1500

_{Review effort: Balanced}