AppliedML LSP for Visual Studio Code

Language support for Applied Meta Language (AppliedML), powered by amlc-lsp. The extension recognizes .aml files, provides basic TextMate highlighting, and exposes the diagnostics and language features advertised by the server.

Server setup

Starting with extension 0.4.3, the client prefers amlcLsp.server.path, then amlc-lsp on PATH or in the active OPAM switch. When none is available, it downloads the matching 0.4.2 server from the official GitHub release. The archive includes the compiler-linked server, GMP, corresponding source and license notices, so no OCaml, OPAM or separate AMLC installation is required. Downloads are SHA-256 verified, bounded, and cached by version and platform in VS Code's extension storage. Completed caches work offline and are reused on restart.

Supported hosts are macOS (Apple Silicon and Intel), Linux (ARM64 and x86_64), and x86_64 Windows. Remote SSH, WSL and Codespaces use the remote host platform. Linux archives target glibc, not Alpine/musl. Unsupported platforms or restricted networks require a local server. Set amlcLsp.server.autoDownload to false to disable automatic downloads. A broken configured or existing server is reported rather than silently replaced; existing local servers require manual upgrades.

For an OPAM-based setup, run AppliedML: Install Language Server with OPAM. After confirmation, the extension installs only amlc-lsp.0.4.2 from its versioned release tag and reconnects automatically. It neither installs nor replaces AMLC.

The installer requires OPAM and AMLC to be available in the same active switch. For 0.4.2, install AMLC from the audited 3a183bc source commit. Older source pins may share the 0.1.0~preview version but expose an incompatible library API. Use the linked manual installation guide to update that pin or an existing server; automatic discovery keeps an existing executable. It stops with guidance when OPAM is unavailable, AMLC is absent, or the AMLC version is incompatible. Set AppliedML › Opam: Path if the OPAM executable is not named opam or is outside Visual Studio Code's PATH.

Nix and manual server installations remain supported. Follow the server installation guide, then set AppliedML › Server: Path to the absolute amlc-lsp executable if Visual Studio Code cannot find it. On Windows, select amlc-lsp.exe. The extension does not bundle the compiler or language server.

Use AppliedML: Show Server Information from the Command Palette to inspect the executable and connected version. The extension warns when the server uses a different major.minor release line.

Features

Compiler-backed diagnostics and completion
Hover, signature help, and symbol navigation
References and guarded rename
Quick fixes and indentation formatting
Semantic tokens, folding, and selection ranges

Exact behavior and cross-file limits are documented in the server README.

Settings

Setting	Purpose
`amlcLsp.server.path`	Explicit server path; empty uses local discovery then download
`amlcLsp.server.autoDownload`	Download a prebuilt server when none is available (default: true)
`amlcLsp.server.arguments`	Additional server arguments
`amlcLsp.server.environment`	Environment variables added to the server process
`amlcLsp.opam.path`	OPAM executable used to find or install the server
`amlcLsp.dialect`	`auto`, `appliedml`, or `legacy` syntax selection
`amlcLsp.trace.server`	LSP message tracing in the AppliedML output channel

Changes to the server or OPAM path, automatic-download setting, arguments, or environment restart the server automatically. The AppliedML: Restart Language Server command remains available for manual recovery.

Privacy and workspace support

Analysis runs locally. This extension does not send source code or telemetry to Arkenstone Labs. Automatic setup contacts GitHub for public release metadata and the platform archive; it does not upload workspace contents. Because it starts a local executable and requires ordinary files, it is disabled for untrusted and virtual workspaces. Remote SSH, WSL, and Codespaces run the extension and server in the remote workspace environment.

Development

cd vscode
npm ci
npm run compile
code --extensionDevelopmentPath="$PWD"

Run npm test for the Extension Host integration test. It downloads VS Code 1.100.0 into the ignored .vscode-test directory and verifies activation, diagnostics, completion, automatic restart, and version compatibility.

For the optional real-download test, run AMLC_PREBUILT_TEST=1 npm test. The runner creates and cleans up a fresh isolated profile. It disables PATH and OPAM discovery, verifies the downloaded compiler-backed server's editor features, and checks cache reuse on restart. The separate downloaded-server CI job runs this test on all five supported host targets and preserves Extension Host logs. It requires public release assets and GitHub connectivity; the regular extension tests continue to use a local fixture server.

GitHub's anonymous API rate limit is shared by clients on the same public IP. CI uses its read-only workflow token for release metadata. On restricted shared networks, optionally set AMLC_LSP_GITHUB_TOKEN in the extension host's environment before launching VS Code. It is used only for this repository's pinned release metadata request, never for archive downloads or asset redirects, and is not passed to the language server. No token is needed for normal setup, and the extension does not request GitHub sign-in.

AppliedML LSP