Loading node_modules Resources in VSC WebView

Recently, while developing the gitlink plugin, I encountered an issue loading node_modules resources in WebView. Although CDN resources could be used directly, loading local resources is faster. Here’s how to solve the loading of node_modules resources.

Configuration

1. Install npm dependency

npm install @highlightjs

Note that this should be a dependency, not a dev dependency.

2. Configure localResourceRoots in webview

 const panel = vscode.window.createWebviewPanel(
            'codeImage',
            'Code Snippet Image',
            vscode.ViewColumn.Beside,
 {
                enableScripts: true,
                retainContextWhenHidden: true,
                localResourceRoots: [
                    vscode.Uri.joinPath(extensionContext.extensionUri),
 ]
 }
 );

Here, we use extensionContext.extensionUri as localResourceRoots, allowing us to access node_modules resources within the extension.

3. Load resources in webview

<link rel="stylesheet" href="node_modules/@highlightjs/cdn-assets/styles/github-dark.min.css">

Please note that relative path syntax is preferred over absolute path syntax. Absolute paths are not supported, but web addresses are.

4. Handle HTML href paths

const readHtml = async (htmlPath: string, panel: vscode.WebviewPanel) =>
 (fs.readFileSync(htmlPath, {
        encoding: 'utf8'
 }))
 .replace(/%CSP_SOURCE%/gu, panel.webview.cspSource)
 .replace(
        /(src|href)="([^"]*)"/gu,
 (_, type, src) =>
          `${type}="${panel.webview.asWebviewUri(
            vscode.Uri.file(path.resolve(htmlPath, '../../../', src))
 )}"`
 );


this._panel.webview.html = await this._getHtmlContent(code, language, options);

 let htmlTemplate = await readHtml(
            path.resolve(this._extensionContext.extensionPath, 'resources/webview/index.html'),
            this._panel
 );

This is how I handle it - processing all resources in the HTML based on the HTML’s location to obtain the path relative to the extension for node_modules resources.

Note

• Don’t add the node_modules folder in the .vscodeignore file. Otherwise, the package won’t include node_modules.

At the end

Following these steps solves the issue of loading node_modules resources in WebView. When updates are needed in the future, run the npm update and repackage the extension.