- Run the [`Launch Extension`](https://github.com/microsoft/vscode/blob/master/extensions/html-language-features/.vscode/launch.json) debug target in the Debug View. This will:
- Open a `.html` file to activate the extension. The extension will start the HTML language server process.
- Add `"html.trace.server": "verbose"` to the settings to observe the communication between client and server in the `HTML Language Server` output.
- Debug the extension and the language server client by setting breakpoints in`html-language-features/client/`
- Debug the language server process by using `Attach to Node Process` command in the VS Code window opened on `html-language-features`.
- Pick the process that contains `htmlServerMain` in the command line. Hover over `code-insiders` resp `code` processes to see the full process command line.
- Set breakpoints in `html-language-features/server/`
If you want to fix html issues or make improvements, you should make changes at [microsoft/vscode-html-languageservice](https://github.com/microsoft/vscode-html-languageservice).
However, within this extension, you can run a development version of `vscode-html-languageservice` to debug code or test language features interactively:
#### Linking `vscode-html-languageservice` in `html-language-features/server/`
- Open both `vscode-html-languageservice` and this extension in two windows or with a single window with the[multi-root workspace](https://code.visualstudio.com/docs/editor/multi-root-workspaces) feature
- Run `yarn watch` at `html-languagefeatures/server/` to recompile this extension with the linked version of `vscode-html-languageservice`
- Make some changes in `vscode-html-languageservice`
- Now when you run `Launch Extension` debug target, the launched instance will use your development version of `vscode-html-languageservice`. You can interactively test the language features.
