Rook for VS Code

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Support for Rook, a language with the semantics of JavaScript, Go-style syntax and static types, in .rk files: highlighting, errors as you type and completion.

Errors and completion

The extension starts a language server with the Rook compiler. While you type, it underlines the errors and warnings that rook build would print, and it completes:

• names in scope: variables, parameters, functions, classes, components, globals such as document, and keywords;
• members after . and ?., with their types: of classes (private ones only inside the class), interfaces, objects, strings, arrays and the DOM;
• types where a type is written: let user Us|;
• tags and components in markup, <Ca|, and the properties of a component or the attributes and events of an element, <input on|.

The types of the standard library and the DOM come from TypeScript's lib files, which the extension carries. Imports of other .rk files and of packages with types are checked as in rook build. Markup and components are errors unless the nearest package.json turns them on with "rook": { "markup": true }, as for rook build.

Highlighting

It highlights:

• keywords, the declarations func, comp, class, interface, type, state and mount();
• Go-style types: number, []Todo, ?User, names of classes and interfaces;
• strings, template strings with ${...}, numbers, comments;
• markup: tags, components, attributes, on*, bind:value, expressions in {...}, and if, for and switch inside it.

The extension also sets up comments (Cmd+/), closing brackets and quotes, and a 4-space indent.

Installation

Search for "Rook Language" in the Extensions view of VS Code, or install it from the Visual Studio Marketplace. VSCodium, Cursor and other editors that use Open VSX find it there. From the command line:

code --install-extension Qwern9876r.rooklang

The extension carries its own copy of the compiler, so it needs nothing else. To build and run .rk files, install the compiler too: npm install --save-dev rooklang.

Building from source

From the root of the repository:

npm run vscode:install

The command bundles the client and the language server with the compiler into editors/vscode/dist (npm run vscode:build), packs editors/vscode/rooklang.vsix and installs it with code. After changes to the grammar or the compiler, run it again and reload the VS Code window.

For working on the extension, a window with it loaded straight from this folder is handier; build it first:

npm run vscode:build
code --extensionDevelopmentPath="$PWD/editors/vscode"

The sources of the extension are in src/: extension.mts starts the server, server.mts answers VS Code, and completion itself is in the compiler (src/completion.ts and the last layer of the checker, src/checker/completion.ts). They are tested in tests/completion.test.ts and tests/vscode-server.test.ts.

The grammar is checked by the tests in tests/vscode-grammar.test.ts with the same engine that VS Code uses (vscode-textmate). The scopes under the cursor are shown by the command "Developer: Inspect Editor Tokens and Scopes".

Limitations

As with rook build, a file with a syntax error shows only its syntax errors: the types are checked once it parses. A file sees the other .rk files it imports as they are saved on disk.

The highlighting is a TextMate grammar: it looks at the text of a line, not at a syntax tree. So:

• < is taken as the start of markup if there is no value before it (a name, ) or ]) and a tag name right after it. a < b and i<n are comparisons, and return <div> is markup;
• types are recognized by their look: the built-in ones (number, string…) and names with a capital letter. Your own types with a lowercase letter (type id = number) are highlighted as ordinary names.