Simula (sim) — VS Code extension

Production-oriented VS Code / Cursor extension for Simula (.sim).

See docs/LSP.md (server capabilities) and PUBLISH.md (release).

Features

Language registration (simula) with syntax highlighting, indentation rules, and snippets
LSP via sim lsp — diagnostics, hover, completion, rename, format, semantic tokens, type definition, remote-attribute navigation, etc.
Workspace trust — language server starts only in trusted workspaces
Commands: restart server, show output, explain diagnostic, open docs, check/run/compile current file
Tasks: sim task type with $sim problem matcher (ariadne ╭─[file:line:col] output)
Status bar with server state and version tooltip
Get Started walkthrough (Simula: Get Started with Simula in walkthroughs view)

Prerequisites

A sim executable on your PATH (or set simula.languageServerPath).

Build from this repository:

cargo build --release   # from repo root

Then set simula.languageServerPath to target/release/sim, or put that binary on your PATH.

Node.js 20+ for building the extension.

Development

cd editors/vscode
npm install
npm run compile
npm test
npm run lint

Press F5 (or open simula.code-workspace and run the extension host).

End-to-end smoke (downloads VS Code):

npm run test:e2e

Debugging (interpreter)

The extension contributes debugger type sim, backed by sim dap (statement-level interpreter stepping).

Open a .sim file
Set breakpoints in the gutter (optional; default stops on entry)
Run Debug: Start Debugging (F5) and choose Debug Simula (interpreter)

Requires a resolved sim binary (same as the language server).

Native / CodeLLDB (optional)

For AOT binaries compiled with sim compile -g, install CodeLLDB and use a type: lldb launch config (macOS / Linux / Windows DWARF-in-PE) — see docs/DEBUG.md. Prefer the contributed sim debugger for day-to-day Simula stepping. Visual Studio PDB is not emitted yet.

Settings

Setting	Default	Description
`simula.languageServerPath`	`sim`	Executable (`${workspaceFolder}` supported). First run searches `PATH` if missing.
`simula.languageServerArgs`	`["lsp"]`	Arguments passed when starting the language server
`simula.trace.server`	`off`	LSP trace level
`simula.allowSquareBracketSubscripts`	`true`	Passed to LSP (init + live config sync)
`simula.allowDoubleDashComments`	`true`	Passed to LSP (init + live config sync). `--` is a line comment when true.
`simula.checkOn`	`change`	When to diagnose: `open` / `change` / `save`
`simula.debounceMs`	`200`	Debounce for change-triggered analysis
`simula.enableHeadingTypeInlayHints`	`true`	Ghost types next to untyped formals in class/procedure headings

Semantic highlighting

Colors come from the active color theme. Simula classifies tokens with language-specific types (type for integer/procedure, boolean for true, character for 'A', parenthesis/semicolon for punctuation, plus the usual keyword/class/function/variable). Themes color those types; you can override a type for Simula only in settings.json. Reload the extension host after changing the language server if an open .sim file still shows the old classification.

To override a token type for Simula only, add to settings.json:

{
  "editor.semanticTokenColorCustomizations": {
    "[Default Dark+]": {
      "rules": {
        "class.simula": "#4EC9B0",
        "function.simula": "#DCDCAA",
        "variable.simula": "#9CDCFE"
      }
    }
  }
}

Tasks

Example .vscode/tasks.json entry (uses the contributed $sim problem matcher):

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "sim: check current file",
      "type": "shell",
      "command": "sim",
      "args": ["check", "${file}"],
      "group": "build",
      "problemMatcher": ["$sim"]
    },
    {
      "label": "sim: run current file",
      "type": "shell",
      "command": "sim",
      "args": ["run", "${file}"],
      "group": "test",
      "problemMatcher": []
    }
  ]
}

Prefer the language server Problems panel for day-to-day editing. Contributed type: "sim" tasks use the same sim executable as LSP/DAP:

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "sim: check current file",
      "type": "sim",
      "command": "check",
      "args": ["${file}"],
      "group": "build",
      "problemMatcher": ["$sim"]
    }
  ]
}

Package

npm run package

Install the .vsix via Extensions → ... → Install from VSIX.

License

MIT — see LICENSE.

Simula

Eirik Sletteberg