VS Code

The extension in editors/vscode gives VS Code:

• highlighting for .volt files, and the file icon, refined by the server’s semantic tokens: types, generic parameters, traits, namespaces, methods, fields, enum variants and vals each by meaning;
• diagnostics as you type, hover, go to definition, find references, the outline, completion and signature help, from voltc lsp;
• inlay hints (the types of locals and closure parameters that don’t write one, parameter names at calls, what a long block closes), code lenses (references, the fns and traits attached to a type, Run above main), highlights, rename, folding and quick fixes (see the language server);
• Volt: Expand Comptime (command palette): what the comptime code on the cursor’s line (or in the file) became, beside it: values, comptime if branches, generic instances, built types, the fns comptime fns declared and @derive output;
• snippets (main, fn, attach, struct, enum, error, match, for, usec…);
• bolt tasks (check, build, build –release, run, test, clean) in folders with a bolt.toml, and the $volt problem matcher, which links voltc’s errors to the code.

From a checkout, one command builds the extension and installs it into VS Code:

cd editors/vscode
npm install && npm run install-extension

The extension finds voltc the way a terminal would, so it works when VS Code was started from a desktop menu (which doesn’t read ~/.bashrc): volt.serverPath when it’s a path, then VS Code’s PATH, then your login shell’s PATH, then ~/.local/bin, then a Volt checkout in a workspace folder or ~/volt (voltc/target/release/voltc, then debug). bolt, for tasks, is found the same way. The status bar shows Volt while the server runs, with the voltc it found in its tooltip; click it to restart the server. If no voltc is found, a notice says so, with Set path and Install guide.

The server finds std the way voltc does ($VOLT_STD, or a std/ next to voltc); volt.stdPath overrides that.

VS Code’s own editor.inlayHints.enabled turns every inlay hint on or off. Changing one of these settings restarts the server.

Volt: Restart Language Server restarts the server, after rebuilding voltc for example. Volt: Run This Program runs the open file (bolt run in a bolt package, else voltc run), as the Run lens above main does.

Terminal → Run Task → bolt lists the tasks. Define your own in .vscode/tasks.json:

{
  "version": "2.0.0",
  "tasks": [
    {
      "type": "bolt",
      "command": "build",
      "args": ["--profile", "small"],
      "problemMatcher": ["$volt"],
      "group": "build"
    }
  ]
}

npm test, run in editors/vscode, runs the grammar’s tests (the assertion files in editors/vscode/tests/grammar and a snapshot of editors/vscode/tests/snap/sample.volt) and the voltc finder’s tests. After a deliberate grammar change, npx vscode-tmgrammar-snap -u 'tests/snap/*.volt' updates the snapshot.

VOLTC=/path/to/voltc npm run test:e2e runs the extension in a real VS Code (downloaded into .vscode-test/ the first time; under xvfb-run without a display). voltc is only in a checkout inside the test’s workspace, not on PATH (the editor gets a HOME of its own, so no shell profile adds one), and the test waits for an error in a broken file, completion after std::, a hover, semantic tokens, an inlay hint, the code lenses and Volt: Expand Comptime on a generic call.