test_browser: collect coverage for qunit tests

This will collect coverage data from the test runs and write .lcov files
into `lcov/` with names like `qunit-base1-test-fsinfo-html.info.gz`.
Nothing is done with these files yet, but you can manually inspect them
using `lcov`.

build.js

@@ -37,6 +37,7 @@ const pkgOptions = {
 
 // context options for qunit tests in qunit/
 const qunitOptions = {
+    ...!production ? { sourcemap: "linked" } : {},
     bundle: true,
     minify: false,
     nodePaths,

test/common/lcov.py

@@ -32,6 +32,7 @@ import re
 import shutil
 import subprocess
 import sys
+import urllib.parse
 from bisect import bisect_left
 from typing import Any, Mapping, Sequence
 
@@ -159,6 +160,12 @@ def get_dist_map(package):
 
 
 def get_distfile(url, dist_map):
+    path = urllib.parse.urlparse(url).path
+    if path.startswith('/qunit/'):
+        relpath = path[1:]
+        if os.path.exists(relpath) and os.path.exists(f'{relpath}.map'):
+            return DistFile(path[1:])
+
     parts = url.split("/")
     if len(parts) < 3 or "cockpit" not in parts:
         return None

test/pytest/test_browser.py

@@ -1,9 +1,11 @@
 import contextlib
 import glob
 import os
+import re
 import subprocess
 from typing import AsyncIterator
 
+import lcov
 import pytest
 from webdriver_bidi import ChromiumBidi
 from yarl import URL
@@ -60,6 +62,9 @@ async def test_browser(html: str) -> None:
         spawn_test_server() as base_url,
         ChromiumBidi(headless=os.environ.get('TEST_SHOW_BROWSER', '0') == '0') as browser
     ):
+        await browser.cdp("Profiler.enable")
+        await browser.cdp("Profiler.startPreciseCoverage", callCount=False, detailed=True)
+
         await browser.bidi(
             'browsingContext.navigate',
             context=browser.context,
@@ -101,6 +106,9 @@ async def test_browser(html: str) -> None:
         if error_message is not None:
             pytest.fail(f'Test failed: {error_message}')
 
+        coverage = await browser.cdp("Profiler.takePreciseCoverage")
+        lcov.write_lcov(coverage['result']['result'], outlabel=re.sub(r'[^A-Za-z0-9]+', '-', html))
+
 
 # run test-timeformat.ts in different time zones: west/UTC/east
 @pytest.mark.asyncio