Emerald Lang for Visual Studio Code

Visual Studio Code support for Emerald, a friendly programming language you'll enjoy writing.

Requirements

The extension needs Emerald itself. Install Emerald, then open any .em file. If emerald isn't on your PATH, set emerald.serverPath to the executable.

The extension provides:

• syntax highlighting for current Emerald declarations, keywords, literals, operators, annotations, members, and calls;
• interpolated, multiline, and raw strings;
• ordinary, documentation, nested block comments;
• starter snippets for declarations, types, constructors, properties, control flow, lambdas, collections, expressions, errors, resources, calls, and test functions;
• comment toggling, bracket matching, automatic closing, and basic indentation;
• live diagnostics, a document outline, format-on-save, hover, go to definition, find references, rename, and member completion, from the Emerald compiler's own language server (emerald lsp).

The grammar follows the compiler's lexer and grows with the language. Completion offers a value's fields, properties, and methods, the members of a type or namespace written before a dot, and the names in scope. The members of built-in types such as String and List are not offered yet; that is coming in a later release.

The language server

This extension starts emerald lsp and talks to it over stdio; it does not implement any language intelligence itself. That means the emerald executable has to be reachable:

• Build it from the sibling emerald-lang repository (zig build there produces zig-out/bin/emerald) and either put it on your PATH, or
• point the emerald.serverPath setting at it directly (a window reload is needed after changing this setting).

If the server can't be started, the extension shows an error naming the path it tried. emerald.trace.server (off/messages/verbose) logs the JSON-RPC traffic between the extension and the server, in the "Emerald Language Server" output channel, for debugging either side.

Try it locally

The extension needs VS Code 1.91 or newer.

npm install
npm test
npm run package
code --install-extension emerald-vscode-0.2.2.vsix

Open any .em file and select Emerald Lang if VS Code does not choose it automatically. Use Developer: Inspect Editor Tokens and Scopes to inspect the scopes under the cursor.

Development

Open this repository in VS Code and press F5. This builds the extension (via the watch task) and opens the Extension Development Host with it loaded; open examples/sample.em there to inspect the grammar, or any .em file to see live diagnostics and the outline (with emerald on your PATH, or emerald.serverPath set, in that development window).

npm run compile builds once (bundling src/extension.ts with esbuild, then type-checking with tsc --noEmit); npm run watch rebuilds on save. npm run package always rebuilds from a clean dist/ first (vscode:prepublish), so a stray development artifact never ends up in a packaged .vsix.

npm test runs the fast checks (grammar and manifest, test/) with no editor involved. npm run test:integration goes further: it launches a real, downloaded VS Code build with this extension loaded and a real emerald lsp running (via emerald.serverPath, pointed at ../emerald-lang/zig-out/bin/emerald), and exercises diagnostics, document symbols, formatting, hover, go to definition, find references, rename, and completion through it end to end (src/test/extension.test.ts). It launches Electron, which on some Linux setups needs system libraries such as libnspr4/libnss3/libasound2 or a virtual display — see docs/handoff.md if it fails to launch a downloaded VS Code build.