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<h1 id="debugging">Debugging</h1>

<p>Add the options in the <code class="language-plaintext highlighter-rouge">Support for debugging NodeJS tests</code> section from https://github.com/bazelbuild/rules_nodejs/blob/master/common.bazelrc to your project’s <code class="language-plaintext highlighter-rouge">.bazelrc</code> file to add support for debugging NodeJS programs.</p>

<p>Using the <code class="language-plaintext highlighter-rouge">--config=debug</code> command line option with bazel will set a number of flags that are specified there are useful for debugging. See the comments under <code class="language-plaintext highlighter-rouge">Support for debugging NodeJS tests</code> for details on the flags that are set.</p>

<p>Use <code class="language-plaintext highlighter-rouge">--config=debug</code> with <code class="language-plaintext highlighter-rouge">bazel test</code> as follow,</p>

<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>bazel test --config=debug //test:...

</code></pre></div></div>

<p>or with <code class="language-plaintext highlighter-rouge">bazel run</code>,</p>

<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>bazel run --config=debug //test:test1

</code></pre></div></div>

<p>to also turn on the NodeJS inspector agent which will break before any user code starts. You should then see,</p>

<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>Executing tests from //test:test1

-----------------------------------------------------------------------------

Debugger listening on ws://127.0.0.1:9229/3f20777a-242c-4d18-b88b-5ed4b3fed61c

For help, see: https://nodejs.org/en/docs/inspector

</code></pre></div></div>

<p>when the test is run.</p>

<p>To inspect with Chrome DevTools 55+, open <code class="language-plaintext highlighter-rouge">chrome://inspect</code> in a Chromium-based browser and attach to the waiting process.

A Chrome DevTools window should open and you should see <code class="language-plaintext highlighter-rouge">Debugger attached.</code> in the console.</p>

<p>See https://nodejs.org/en/docs/guides/debugging-getting-started/ for more details.</p>

<h2 id="debugging-with-vs-code">Debugging with VS Code</h2>

<p>With the above configuration you can use VS Code as your debugger.

You will first need to configure your <code class="language-plaintext highlighter-rouge">.vscode/launch.json</code>:</p>

<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>{

"type": "node",

"request": "attach",

"name": "Attach nodejs_binary",

"internalConsoleOptions": "neverOpen",

"sourceMapPathOverrides": {

"../*": "${workspaceRoot}/*",

"../../*": "${workspaceRoot}/*",

"../../../*": "${workspaceRoot}/*",

"../../../../*": "${workspaceRoot}/*",

"../../../../../*": "${workspaceRoot}/*",

// do as many levels here as needed for your project

}

</code></pre></div></div>

<p>We use <code class="language-plaintext highlighter-rouge">sourceMapPathOverrides</code> here to rewrite the source maps produced by <code class="language-plaintext highlighter-rouge">ts_library</code> so that breakpoints line up with the source maps.

Once configured start your process with</p>

<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>bazel run --config=debug //test:test1

</code></pre></div></div>

<p>Then hit <code class="language-plaintext highlighter-rouge">F5</code> which will start the VS Code debugger with the <code class="language-plaintext highlighter-rouge">Attach nodejs_binary</code> configuration.

VS Code will immediatenly hit a breakpoint to which you can continue and debug using all the normal debug features provided.</p>

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