Power Automate WDL Expression Tools

Write, understand, validate, and reformat standalone Microsoft Power Automate and Azure Logic Apps Workflow Definition Language (WDL) expressions without leaving Visual Studio Code.

This extension adds a dedicated .wdlexpr language mode with syntax highlighting, AST-aware formatting and minification, function help, completion, signature help, and conservative diagnostics.

Quick start

1. Install Power Automate WDL Expression Tools in Visual Studio Code.
2. Create a file whose name ends in .wdlexpr.
3. Paste or write one Power Automate or Logic Apps expression.

For an unsaved scratch expression, open the Command Palette and run Power Automate: New WDL Expression.

if(equals(toLower(variables('Status')),'approved'),concat('Hello, ',trim(variables('Name'))),'Pending')

Run Format Document or Power Automate: Format WDL Expression to produce:

if(
    equals(
        toLower(
            variables('Status')
        ),
        'approved'
    ),
    concat(
        'Hello, ',
        trim(
            variables('Name')
        )
    ),
    'Pending'
)

Run Power Automate: Minify WDL Expression to return to a compact form.

Features

• Dedicated .wdlexpr files and Power Automate WDL Expression language mode
• Theme-aware syntax highlighting for calls, literals, access chains, and delimiters
• Document and safe-selection formatting driven by the parsed expression tree
• AST-aware minification that preserves WDL string escaping
• Hover documentation for all 137 functions in Microsoft's workflow expression function reference
• Function completion with snippet tab stops
• Signature help that follows nested and incomplete calls
• Problems-panel diagnostics for syntax, unknown functions, argument counts, and provable argument-type errors
• Cached document analysis shared by editor providers

Function metadata ships with the extension. Hover and completion do not fetch documentation while you edit.

Commands

The format and minify commands only change Power Automate WDL Expression editors. Incomplete or unsafe input is left unchanged and VS Code displays an explanation.

VS Code's standard Format Document and Format Selection commands are also supported. A selection must contain one complete expression.

Settings

All settings are resource-scoped, so they can be configured for a user, workspace, folder, or language.

Diagnostics

Diagnostics use stable code families:

Analysis is intentionally conservative. Runtime values from flow variables, actions, triggers, properties, and connectors remain unknown rather than producing speculative errors.

Current limitations

• A .wdlexpr file contains one standalone expression; this is not a complete flow-definition editor.
• The extension does not connect to Power Platform, inspect a flow, or discover action, variable, trigger, or connector schemas.
• The bundled catalog follows Microsoft's workflow expression function reference; availability can still vary by Power Automate or Logic Apps environment.
• No .wdl file association is registered, to avoid claiming unrelated WDL formats.
• Diagnostics are static editor guidance, not a substitute for validating and running the expression in its target flow.

Requirements

• Visual Studio Code 1.125 or newer
• No Power Platform sign-in is required

Development

Install dependencies and run the fast repository checks:

npm ci
npm run validate

Run the Extension Host suite separately, or run every local quality gate:

npm run test:integration
npm run test:all

The integration suite launches a clean VS Code host and reports a named scenario for language registration, commands, formatting, hover, signature help, completion, and diagnostic lifecycle behavior. It runs against the pinned VS Code version configured by the test runner. On headless Linux, use:

xvfb-run -a npm run test:integration

Pull requests and pushes to main run the same locked install, lint, typecheck, unit-test, and build gates in GitHub Actions. A separate Linux job runs the Extension Host suite under xvfb-run, so editor integration failures remain distinct from the fast language-engine checks. Superseded runs on the same branch are cancelled automatically.

Open the repository in VS Code and run the Run Extension launch configuration for manual development. The Run Extension Integration Tests launch configuration supports interactive test debugging.

The reusable engine lives under src/language and never imports vscode. Editor commands, providers, diagnostics, and lifecycle adapters live under src/extension. See Language engine for the detailed boundary.

Privacy

Expression source is analyzed locally. The extension does not send documents to a remote service and does not include telemetry.

Feedback and license

Report defects and feature requests in the GitHub issue tracker.

Licensed under the GNU Affero General Public License v3.0.