packages/labs/vscode-extension/README.md
The Lit VS Code extension adds Lit syntax highlighting, code completion, type-checking, and other IntelliSense features to VS Code and compatible IDEs.
For local development, the extension must be run in its own window. The "Run Lit VS Code Extension" launch will build the extension and open a new VS Code window.
Then you open a project to use the extension with. Make sure you use the File > "Add folder to workspace..." menu so that the folder is opened in the extension development window. Using the "Open Folder" button in the extension development window will unfortunately open the folder in a plain window without the local extension running.
The Lit Extension adds a "Hello Lit" command that you can use to check that the extension is loaded. Running the command should show a "Hello from Lit!" message in a toast and log a nessage to the "Lit" log.
Logs are important for extension development. You can see the logs in the Output tab of the VS Code panel. There's a dropdown with available logs. Useful logs are "Lit", "Extension Host", and "Window". If things aren't working look for exceptions in these logs.
For some reason the build script is not updating the output files when run while the extension is running. This could be a conflict from multiple invocations of Wireit - one via tasks.json and one from a commandline. Unfortunately that means you have to close the extension development window to load a new build.
When this is fixed, then you should be able to run the "Developer: Reload Window" command to load a new build of the extension or its dependencies.
Make that you've read through the extensions guidelines.