ripr: Static Mutation Exposure

Preview VS Code/Open VSX extension for ripr, a static Rust analysis tool that finds changed code where the nearby tests may run but not actually check the changed behavior.

It is a fast static companion to mutation testing: it does not run mutants, but it points reviewers and coding agents at the focused test most likely to matter. The extension starts ripr lsp --stdio, surfaces saved-workspace diagnostics, and helps a human or coding agent move from a flagged change to one focused test.

Requirements

The extension can download and cache the matching ripr server binary from GitHub Releases on first activation. Manual installation is still supported for offline, pinned, or enterprise-controlled environments.

Install and First Run

Install EffortlessMetrics.ripr from VS Code Marketplace or Open VSX. The extension should resolve its server automatically, so cargo install ripr is a fallback rather than a required first step.

After opening a Rust/Cargo workspace:

1. Check the ripr status bar item for the current state: server status, workspace, analysis progress, the recommended next action, "no focused test gap found," or "analysis stale / failed." The status bar projects an existing workspace-matched target/ripr/reports/first-useful-action.json report when one is present, without rerunning analysis. (Internal status IDs such as no-actionable-seam and first-useful-action remain stable in JSON.) Run ripr: Show Status when no diagnostics appear; it prints the workspace root, server source and command, editor selectors, enabled languages from the last refresh, and the next safe action.
2. Use the Problems panel to find changed code that ripr flagged as mutation-exposed in the saved workspace.
3. Hover a flagged location to see why ripr thinks the current tests are weak: the assertion or check that appears to be missing, the related test to imitate, a suggested test shape, and verify and receipt commands.
4. Use the intent-titled code actions to copy the targeted test brief, the suggested assertion, or the agent handoff command chain.
5. Open the best related test when ripr finds an imitation target.
6. Add one focused test outside the editor.
7. Verify with the copied command chain or the CI artifact packet.
8. Emit the receipt, refresh saved-workspace analysis, then inspect the first-pr start-here packet when the status reports that one is safe.

Unsaved-buffer overlays are not enabled by default.

For the full editor loop from diagnostic to receipt, see docs/EDITOR_FIRST_RUN_TO_FIRST_RECEIPT.md. For the local handoff from receipt to first-pr packet, see docs/EDITOR_FIRST_PR_BRIDGE_WORKFLOW.md.

What ripr Does

ripr scans Rust code for mutation-exposed locations — places where the changed behavior could plausibly differ — and reports whether nearby tests appear to contain an assertion or check that would catch the change. It uses conservative static language and is meant to guide the next useful test, not to prove test adequacy.

Under the hood, ripr uses the RIPR model: reachability, infection, propagation, and revealability. Reports, JSON, and specs use the precise internal vocabulary (seams, discriminators, oracle strength); the editor surface keeps that vocabulary out of the first-hour path. See the Terminology bridge to map between the two.

The 0.8.x extension surfaces saved-workspace diagnostics, evidence-aware hovers, intent-titled code actions for inspecting the flagged change / writing the targeted test / copying the agent handoff / verifying after the test / reviewing the receipt / refreshing analysis, an LSP collectEvidenceContext seam handoff packet, and a first-useful-action projection in the status bar and hover when a workspace-matched report already exists. It also projects existing first-pr start-here packet state in Diagnose Setup and Show Status, and can open or copy bounded first-pr packet content only after the packet validates against the current workspace and diagnostic identity.

It does not run mutation testing, report killed/survived, or prove test adequacy. Use real mutation testing, such as cargo-mutants, for ready-mode confirmation.

Settings

• ripr.server.path: explicit path to the ripr executable. Empty by default.
• ripr.enabled: enables saved-workspace diagnostics, hovers, status, and code actions. Defaults to true.
• ripr.server.args: arguments used to start the language server. Defaults to ["lsp", "--stdio"].
• ripr.server.autoDownload: download a matching server when needed. Defaults to true.
• ripr.server.version: pinned server version. Empty means match the extension version.
• ripr.server.downloadBaseUrl: override the manifest location for internal mirrors.
• ripr.check.mode: preferred editor check mode. Defaults to draft.
• ripr.baseRef: Git base ref used by context commands. Defaults to origin/main.
• ripr.trace.server: language-server trace setting.

Commands

• ripr: Restart Server
• ripr: Diagnose Setup
• ripr: Show Status
• ripr: Show Output
• ripr: Start Current Repair
• ripr: First PR - Open Packet
• ripr: First PR - Copy Summary
• ripr: First PR - Copy Repair Packet
• ripr: First PR - Copy Verify Command
• ripr: First PR - Copy Receipt Command
• ripr: First PR - Copy Regeneration Guidance
• ripr: Inspect Test Gap - Copy Context
• ripr: Write Targeted Test - Copy Suggested Assertion
• ripr: Write Targeted Test - Copy Brief
• ripr: Agent Handoff - Copy Packet Command
• ripr: Agent Handoff - Copy Brief Command
• ripr: Verify After Test - Copy After Snapshot Command
• ripr: Verify After Test - Copy Verify Command
• ripr: Review Result - Copy Receipt Command
• ripr: Write Targeted Test - Open Best Related Test
• ripr: Open Settings

Preview Limitations

The 0.8.x extension uses a universal VSIX and downloads native server binaries from matching GitHub Releases when available. It does not auto-install Rust tooling, run mutation tests, make automatic edits, or analyze unsaved buffer overlays by default. Bundled platform-specific VSIXs are planned after the downloader path is proven.