Skip to main content
Mobile Developmentdotnet

find-regression-risk

(No description provided in SKILL.md frontmatter.)

Stars
23,266
Source
dotnet/maui
Updated
2026-05-30
Slug
dotnet--maui--find-regression-risk
View on GitHubRaw SKILL.md

// install — copy + paste into any project

mkdir -p .claude/skills && curl -fsSL https://raw.githubusercontent.com/dotnet/maui/HEAD/.github/skills/find-regression-risk/SKILL.md -o .claude/skills/find-regression-risk.md

Drops the SKILL.md into .claude/skills/find-regression-risk.md. Works with Claude Code, Cursor, and any agent that loads SKILL.md files from .claude/skills/.

find-regression-risk

Detects potential regression risks in a PR by cross-referencing removed lines against lines added by recent labeled bug-fix PRs.

How It Works

Purely mechanical — no AI/LLM. Five-step algorithm:

  1. PR diff — collects lines REMOVED by the PR under review.
  2. Git history — git log --follow --since=6mo finds recent PRs that touched the same files.
  3. Label filter — keeps PRs (or their linked issues) labeled i/regression, t/bug, p/0, or p/1.
  4. Fix diff — fetches each fix PR's diff and collects lines it ADDED to the same file.
  5. Compare — whitespace-insensitive string equality:
    • 🔴 REVERT — removed line matches a line a fix PR added (highest risk).
    • 🟡 OVERLAP — same file modified, but no exact line revert.
    • 🟢 CLEAN — no bug-fix PRs touch the same files.

Standalone Invocation

# Analyze a specific PR (auto-detects files)
pwsh -NoProfile -Command '& ./.github/scripts/Find-RegressionRisks.ps1 -PRNumber 33908 -OutputDir /tmp/out'

# Analyze specific files only
pwsh -NoProfile -Command '& ./.github/scripts/Find-RegressionRisks.ps1 -PRNumber 33908 -OutputDir /tmp/out -FilePaths @("src/Core/src/Platform/Android/MauiWindowInsetListener.cs")'

Parameters

Parameter Required Default Description
-PRNumber Yes — PR number to analyze
-Repo No dotnet/maui Repository in owner/name form
-FilePaths No auto-detect Implementation files to check
-MonthsBack No 6 History window for git log
-MaxRecentPRsPerFile No 20 Rate-limit guard per file
-BaseBranch No main Base branch for git log scope
-OutputDir No — Directory for output files
-WriteInlineFindings No off Emit inline-findings.json

Outputs

When -OutputDir is specified:

  • result.txt — single token: CLEAN, OVERLAP, or REVERT
  • risks.json — structured findings for downstream agents
  • content.md — markdown summary for the PR comment
  • inline-findings.json — (only with -WriteInlineFindings) inline annotations

Integration

The script runs as STEP 4 in Review-PR.ps1 (Regression Cross-Reference, after UI test detection and before the Gate step). Its content.md is assembled into the AI summary comment by post-ai-summary-comment.ps1.

When REVERT risks are detected, the regression tests from the reverted fix PRs are executed:

  • UI tests → BuildAndRunHostApp.ps1 -Platform <plat> -TestFilter <filter>
  • Device tests → Run-DeviceTests.ps1 -Project <proj> -Platform <plat> -TestFilter <filter>
  • Unit/XAML tests → dotnet test <project> --filter <filter>

The expert reviewer agent (maui-expert-reviewer.md, dimension #6) reads risks.json to check for REVERT entries.

Known Limitations

  • Inline findings: The -WriteInlineFindings flag emits deletion-side (LEFT) annotations, but post-inline-review.ps1 currently only posts RIGHT-side comments. LEFT-side findings are silently dropped. This is documented as future work.
  • Whitespace-only changes: By design, an indent-only change to a fix line won't trigger a REVERT (the normalization collapses whitespace). This avoids false positives from reformatting.
  • pwsh -File array parameters: When invoking standalone from bash, use pwsh -Command '& ./script.ps1 -FilePaths @(...)' syntax. pwsh -File doesn't evaluate @() expressions.

Tests

pwsh -NoProfile -File .github/scripts/tests/Test-FindRegressionRisks.ps1