find-regression-risk

# 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 ```powershell # 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` | | `-DiffFile` | No | live PR diff | Frozen diff of the current PR; historical fix diffs are fetched normally | | `-ChangedPathsFile` | No | live auto-detection | Frozen JSON array of changed file paths | | `-StrictEvidence` | No | off | Fail on unavailable history/API evidence instead of reporting no match | ## 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 review 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. The standalone `/review expert-review` gh-aw collector supplies its frozen diff, changed paths and pinned base with `-StrictEvidence`. Collection failures become explicit evidence gaps, not CLEAN results. It inspects regression-test source but does not execute any of those tests. ## 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 ```powershell pwsh -NoProfile -File .github/scripts/tests/Test-FindRegressionRisks.ps1 ```