Koka Syntax Highlighting and Language Server

Syntax highlighting and language server support for the Koka programming language in Visual Studio Code. Visit https://koka-lang.github.io for more information.

Run and edit the standard examples

Open the command panel in VSCode (Ctrl/Cmd + Shift + P), and run the Koka: Open samples command (when you start typing the command will surface to the top).

You can execute any main, test.., and example.. functions directly in the debug console by clicking on the run debug | optimized code lenses displayed above these functions.

(Re)Install the latest Koka compiler

Open the command panel in VSCode (Ctrl/Cmd + Shift + P) and run the Koka: Download and install the latest compiler command. In the extension settings, you can also set the Koka compiler path and specific compiler flags manually.

Inlay hints

The extension shows inlay hints for inferred types of parameters and local declarations. You can toggle the visibility of inlay hints by pressing and holding ctrl+alt (or ctrl+option on MacOS) to show these inlay hints.

Customization

Supported Language Server Aspects

• Diagnostics (parse and type errors)
• Code completion
• Hover information
• Find definitions
• Inlay hints (shows inferred types)
• Document outline
• Code folding ranges
• Code Lenses (run debug and run optimized)
• Jump to definition

Syntax token classes

• koka.conid: constructors.
• koka.op: operators.
• koka.id: identifiers.
• koka.id.decl(.function|.val|.var): declarations.
• koka.id.library(.resume|.finally|...): control related library identifiers.
• koka.moduleid: module identifiers.
• koka.keyword: keywords.
• koka.keyword.control: control flow keywords.
• koka.special: reserved separators ({};, etc).
• koka.special.dot: the dot separator.
• koka.number: numbers.
• koka.string(.invalid|.escape|.raw): string literals.
• koka.char(.invalid|.escape): character literals.
• koka.type(.kind|.special|.typevar|.typecon): types.
• koka.comment(.line|.block): comments.
• koka.comment.doc(.emph|.pre|.pre.type|.pre.block): documentation inside a comment.

Custom launch

You can create custom launch configurations in your launch.json file. The following settings are available:

{
  "type": "koka",
  "request": "launch",
  "program": "",      // The path to the file you want to run
  "name": "",         // The name as you want it to appear in the run configurations dropdown
  "functionName": "", // optional function name to run
  "programArgs": [],  // optional arguments you want to give to the compiled program
  "compilerArgs": "", // optional arguments you want to give to the compiler (e.g. --verbose or -O2)
}

Compilation progress is shown in the language server terminal window, while the debug console shows the output of the program.

Custom syntax colors

You can customize the Koka syntax highlighting by editing the settings.json file of VS Code (press Ctrl/Cmd+Shift+P and select "Open Settings (JSON)" to open it). Then add a editor.tokenColorCustomizations entry, for example:

"editor.tokenColorCustomizations": {
  "textMateRules": [
    { "scope": "koka.type",
      "settings": { "foreground": "#00B8B8" }
    },
    { "scope": "koka.conid, koka.number",
      "settings": { "foreground": "#a6c2a3" }
    },
    { "scope": "koka.comment.doc.pre",
      "settings": { "foreground": "#91ac91" }
    },
    { "scope": "koka.id.decl.function",
      "settings": { "foreground": "#cac199" }
    },
  ]
}