Candela for Visual Studio Code

Editor support for the Candela language (.cdl files): TextMate syntax highlighting, language configuration (comments, brackets, auto-closing, indentation), snippets, and a language server client (live diagnostics, hover, completion, outline, go-to-definition) backed by candela-lsp.

Candela is the scripting language of the Lumen UI framework. It is a fork of keel by Horace Hoff, renamed and extended for Lumen (source file extension .cdl). See the repository NOTICE for attribution details.

Features

• Syntax highlighting for:
  • Keywords: if, else, match, while, for, in, loop, return, break, continue, try, catch, let, fn, struct, enum, impl, import, as, host, dylib.
  • Built-in types: int, float, bool, string, plus user-defined structs and enums.
  • Constants: true, false, null.
  • Strings with escape sequences (\n, \t, \r, \\, \", \0).
  • Integer and float literals.
  • Operators, including the ... variadic marker in host blocks and the .. range operator.
  • import, host, and dylib constructs, struct declarations and literals, enum and impl declarations, function definitions and calls, method calls, and namespace:: access.
• Language configuration: line comments (//), bracket matching, auto-closing and surrounding pairs, and {} indentation rules.
• Snippets, by prefix: main, fn, struct, let, if, ifelse, for, forin, while, loop, match, host, dylib, import, importlib, and print.
• A language server client that launches candela-lsp over stdio for live diagnostics, hover, completion, document symbols (outline), and go-to-definition. See ../../lsp/README.md for the exact scope of each.

Language facts

• Comments: line comments only (// ...). There is no block comment syntax.
• Strings: double-quoted, with the escapes listed above. No string interpolation.
• Numbers: integers are i32 ([0-9]+); floats are f64 and must be written with a decimal point ([0-9]*.[0-9]+).
• Structs: struct Name { field: type, ... }; instantiated with Name { field: value }; fields accessed with x.field.
• Foreign functions: dylib "path" { rettype name(argtypes); ... } for dynamic libraries and host "namespace" { rettype name(argtypes); ... } for host-registered closures. A trailing ... argument marks a variadic host function.
• Modules: import "file.cdl"; for a file, import "std/list"; for a shipped library. A bare import merges the module's symbols into the file's scope; import "..." as alias; keeps them behind alias::.

Language server

This extension launches candela-lsp (a separate crate at ../../lsp/ in this repo) as a subprocess over stdio, the same transport every LSP client uses. It looks for a candela-lsp (or candela-lsp.exe on Windows) binary on PATH by default; set candela.languageServerPath in your settings to point at a specific binary instead (for example, one built locally with cargo build -p candela-lsp from the repo root; see that crate's README for why to avoid --release).

If candela-lsp cannot be started, the extension shows an error message instead of failing silently; the syntax highlighting/snippets/language configuration above keep working either way, since those do not depend on the server.

Install / development

This extension has one runtime dependency (vscode-languageclient) that must be present in node_modules when packaged, so run npm install before packaging. There is no compile step; src/extension.js is plain CommonJS, not TypeScript.

• Install dependencies: npm install (from this directory).

• Run from source: open this folder (editors/vscode) in VS Code and press F5 to launch an Extension Development Host, then open any .cdl file.

• Package a .vsix:

  npm install
  npx --yes @vscode/vsce package
  

  Install the produced .vsix with code --install-extension candela-0.2.0.vsix.

License

Apache-2.0. See the repository LICENSE and NOTICE.