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Janet language support for Visual Studio Code

This extension adds language support and some IDE-lite editor features for the Janet programming language to VS Code.

Just starting with Janet? See the official language introduction here.

Features

  • .janet file type support and syntax highlighting for Janet files
  • Create a Janet REPL session in the integrated terminal (Janet: Start REPL in the Command Palette)
    • Evaluate expressions from any open .janet file (with alt+e) or load the entire open file into the REPL (with alt+l), creating a new one if none is currently active
  • Auto-format Janet code while typing, or format current form on command (with Tab)
  • Structural editing and navigation using ParEdit-style Sexp commands
    • Ctrl+Left/Right to move cursor by S-Exp
    • Alt+Up/Down to drag S-Exp forward/backward
    • "Slurp" (extend parentheses), "Barf" (shrink parentheses), and other PareEdit commands (see this visual guide to ParEdit on the Calva website for more info, most of which applies without modification to this extension too)
  • Language Server Protocol via embedded Janet LSP
    • Inline compiler error underlining
    • Function and macro symbol autocomplete
    • On-hover symbol definitions
    • Pop-up signature helps
    • Document formatting

More coming soon!

Usage

Janet LSP and startup.janet

Janet LSP works by running a copy of the Janet runtime and flychecking (that is, compiling but not fully evaluating) the code in your active editor window using that runtime instance. This allows for on-hover documentation and compiler warnings to be provided by Janet itself.

Sometimes, you may need to pre-load modules or modify the environment table in other ways in order for the LSP's runtime to correctly recognize the code in your editor. In such cases, you can create a .janet-lsp/ directory in your project's root and add a startup.janet file to that folder. If such a startup script is detected, the LSP will fully execute it prior to initiating the startup handshake with your editor.

The code in startup.janet is normal Janet source code that is executed by the server's runtime. Don't put any code you don't completely trust in startup.janet.

Contributing

Issues and PRs are welcome!

Prior Art

Huge portions of this extension are remixed from other open source projects, including: