Mutant Language Tools

VS Code language support for Mutant.

Included in this MVP

• Language Server integration over stdio
• Diagnostics from the Mutant LSP server
• Hover, completion, go to definition, references, and rename
• Starter syntax highlighting via TextMate grammar

Configuration

• mutant.languageServer.path: executable/command path for Mutant LSP (default: empty string; auto-detect packaged binary first, then workspace)
• mutant.languageServer.args: additional CLI args for the server
• mutant.lint.rules.duplicateTopLevelDeclaration.severity: severity for the duplicate declaration lint rule (error, warning, information, hint, off)
• mutant.lint.rules.unusedDeclaration.severity: severity for the unused declaration lint rule (error, warning, information, hint, off)
• mutant.lint.rules.undefinedDeclaration.severity: severity for the undefined identifier lint rule (error, warning, information, hint, off)
• mutant.lint.rules.nestingComplexity.severity: severity for deep nesting diagnostics in function bodies (error, warning, information, hint, off)
• mutant.format.onType.enabled: opt-in on-type formatting while typing (false by default)

By default, Mutant files use editor.formatOnSave: true via extension configuration defaults, so canonical style is enforced when saving. By default, editor.formatOnType remains disabled for Mutant files; enable mutant.format.onType.enabled if you want live formatting while typing.

When mutant.languageServer.path is empty, the extension first tries packaged platform binaries in bin/:

• mlsp-windows-amd64.exe
• mlsp-windows-arm64.exe
• mlsp-linux-amd64
• mlsp-linux-arm64
• mlsp-darwin-amd64
• mlsp-darwin-arm64

If no packaged binary matches the current platform/arch, it then checks common local paths such as mlsp(.exe) in the workspace and parent folder before falling back to command lookup from PATH.

Setting a lint rule severity to off suppresses that rule.

Local Development

1. npm install
2. npm run compile
3. Build the language server binary when needed:

../lsp/build.ps1 -HostOnly

../lsp/build.sh --host-only

This produces mlsp artifacts in lsp/dist/ for local extension use.

4. Press F5 in VS Code to launch the extension development host.

For publishing with bundled binaries:

1. Build all LSP targets:

../lsp/build.ps1

../lsp/build.sh

2. Stage binaries into extension bin/:

npm run prepare:lsp-bins

3. Package/publish the extension. vscode:prepublish already runs prepare:lsp-bins automatically.

Debug configuration is included in .vscode/launch.json and build tasks are in .vscode/tasks.json.

If your LSP binary is not on PATH, set mutant.languageServer.path to an absolute path.

Troubleshooting

For full troubleshooting coverage (PATH setup, settings validation, logs, restart flow), see ../docs/VSCODE_EXTENSION_TROUBLESHOOTING.md.

Quick commands:

• Mutant: Show LSP Status
• Mutant: Show LSP Logs
• Mutant: Copy LSP Logs
• Mutant: Restart LSP

Key settings:

• mutant.languageServer.path
• mutant.languageServer.args

Smoke Test Workflow

1. Run the VS Code task smoke: lsp features.
2. Press F5 to start the extension development host.
3. Run command Mutant: Open Smoke File.
4. Run command Mutant: Run LSP Smoke Checks.
5. Run command Mutant: Show LSP Status to verify server state.
6. Run command Mutant: Show LSP Logs to inspect Mutant-only server logs.
7. Run command Mutant: Copy LSP Logs to copy recent logs for bug reports.
8. If needed, run Mutant: Restart LSP to recover from startup failures.
9. Verify:

• Linting: warning on duplicate top-level answer declaration.
• Semantic colors: keywords, numbers, strings, enum/type identifiers receive semantic highlighting.
• Formatting: run Format Document and confirm trailing spaces are removed and a single final newline remains.

License

This extension is licensed under GNU AGPL v3.0 only.

See LICENSE.