Expressif.LanguageServer

Language Server Protocol support for Expressif, bringing diagnostics, completion, hover information, signature help, semantic highlighting, formatting, quick fixes and expression evaluation to your editor.

The repository also contains Expressif Language Support, a thin Visual Studio Code client that bundles and connects to the language server.

About | Features | Installing | Using Visual Studio Code | Development

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Expressif.LanguageServer exposes editor-independent language features through the Language Server Protocol.

The language server communicates with editors over standard input and output. Editor-specific behavior belongs in thin clients such as the VS Code extension.

The recommended way to use Expressif.LanguageServer today is through the Expressif Language Support VS Code extension.

Download the .vsix package from the latest GitHub release, then install it from Extensions → … → Install from VSIX….

It can also be installed from the command line:

code --install-extension .\Expressif-LanguageSupport-<version>-win-x64.vsix

The packaged extension contains a self-contained language server. A separate .NET installation or language-server installation is therefore not required.

GitHub releases currently provide Windows x64 packages.

A standalone self-contained server is also available from the GitHub releases.

Download and extract:

Expressif-LanguageServer-<version>-net10.0-win-x64.zip

Then configure an LSP-compatible editor or client to launch:

Expressif-LanguageServer.exe

The process communicates using the Language Server Protocol over standard input and output; it is not an interactive command-line application.

Open a .expressif or .expr file after installing the extension. The language server starts automatically and provides diagnostics, completion, hover information, signature help, semantic highlighting, formatting and quick fixes.

Press Ctrl+Shift+Enter (Cmd+Shift+Enter on macOS), select the play button in the editor title, or run Expressif: Run Expression from the Command Palette to choose the input and output format.

If text is selected, only that selection is evaluated. Otherwise, the complete document is evaluated.

The input picker supports no input, an Expressif literal, a JSON or CSV file, an open JSON/CSV editor, the current selection in such an editor, or the previously used input.

After choosing the input, choose the result representation:

.expressif
.json

Evaluation results open as read-only virtual documents beside the Expressif script. .expressif results use Expressif language mode and .json results use JSON language mode. Re-running the same script with the same output format refreshes the existing result editor.

Press Ctrl+Enter (Cmd+Enter on macOS), or run Expressif: Run Expression with Last Input and Output, to evaluate using the most recently selected input and output format. If either choice is unavailable, only the missing choice is requested.

The VS Code extension exposes these settings:

To change evaluation rendering, open VS Code Settings (Ctrl+, or Cmd+,), search for Expressif Output, and choose compact or pretty. When pretty is selected, set Expressif › Output: Indent to the number of spaces to use at each level. The equivalent settings.json configuration is:

{
  "expressif.output.formatting": "pretty",
  "expressif.output.indent": 4
}

Change pretty to compact for single-line results. The indent setting is ignored in compact mode. Changes apply to the next evaluation without reloading VS Code.

Language-server logs and protocol traces are available from View → Output → Expressif Language Server.

Some pieces of the editor experience are deliberately still evolving.

Evaluation results currently use the Output panel. #115 will move them to a regular read-only editor pane.

The language-server extension currently owns the expressif language registration itself. #117 will make it depend on the dedicated Expressif syntax-highlighting extension instead.

Completion is currently based on the function catalog rather than inferred input types. Type-aware ranking is tracked by #58.

Whole-document formatting is available, while formatting as you type is tracked separately by #67.

Additional semantic validation and editor assistance for tuple-binding shorthands is tracked by #102.

Development requires the .NET 10 SDK, Node.js with npm, and Visual Studio Code.

Build and test the language server from the repository root:

dotnet restore Expressif.LanguageServer.sln
dotnet build Expressif.LanguageServer.sln -c Release -f net10.0
dotnet test Expressif.LanguageServer.sln -c Release -f net10.0

Build the VS Code client with:

cd vscode-extension
npm ci
npm run compile

For a local extension-development session, publish a self-contained server into the extension first:

node ./scripts/publish-server.mjs

Then open the repository in VS Code and press F5 to launch the Extension Development Host.

The VS Code client is intentionally thin: parsing, diagnostics and language semantics remain in Expressif.LanguageServer and its Core project rather than being duplicated in TypeScript.

See CONTRIBUTING.md for contribution guidelines and SECURITY.md for reporting security issues.

Expressif.LanguageServer is licensed under the Apache License 2.0.