https://github.com/python/cpython/commit/9587726a3ebbcdb780e3f15c9e016e3a28c646e3
commit: 9587726a3ebbcdb780e3f15c9e016e3a28c646e3
branch: main
author: László Kiss Kollár <[email protected]>
committer: pablogsal <[email protected]>
date: 2026-05-09T14:05:46+01:00
summary:
gh-149430: Fix edge-cases in `profiling.sampling` outputs (#149431)
The line highlights on the heatmap are driven by the URL hash and the
`:target` selector. When clicking a caller/callee link for the line that
was already selected, the hash doesn't change, so the browser keeps the
existing target state and doesn't restart the animation. Due to this the
highlight only works the first time.
With this fix, line navigation goes through JavaScript. If the target
URL already points to the current location, the highlight is replayed by
clearing the animation, forcing style recalculation, and restoring it.
The `baseline_self` variable isn't initialized for structural elided
roots. This variable is accessed later unconditionally and leads to a
crash.
The child process ends up being invoked with `--diff_flamegraph` instead
of the correct argument.
files:
M Lib/profiling/sampling/_heatmap_assets/heatmap.js
M Lib/profiling/sampling/cli.py
M Lib/profiling/sampling/stack_collector.py
M Lib/test/test_profiling/test_sampling_profiler/test_children.py
M Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
diff --git a/Lib/profiling/sampling/_heatmap_assets/heatmap.js
b/Lib/profiling/sampling/_heatmap_assets/heatmap.js
index 2da1103b82a52a..1f698779f3a46e 100644
--- a/Lib/profiling/sampling/_heatmap_assets/heatmap.js
+++ b/Lib/profiling/sampling/_heatmap_assets/heatmap.js
@@ -84,7 +84,7 @@ function showNavigationMenu(button, items, title) {
item.appendChild(funcDiv);
item.appendChild(createElement('div', 'callee-menu-file',
linkData.file));
- item.addEventListener('click', () => window.location.href =
linkData.link);
+ item.addEventListener('click', () => navigateToLine(linkData.link));
menu.appendChild(item);
});
@@ -105,7 +105,7 @@ function handleNavigationClick(button, e) {
const navData = button.getAttribute('data-nav');
if (navData) {
- window.location.href = JSON.parse(navData).link;
+ navigateToLine(JSON.parse(navData).link);
return;
}
@@ -117,11 +117,29 @@ function handleNavigationClick(button, e) {
}
}
+function restartLineHighlight(target) {
+ target.style.animation = 'none';
+ // Force style recalculation so restoring the animation restarts it.
+ void target.offsetWidth;
+ target.style.animation = '';
+}
+
+function navigateToLine(link) {
+ const url = new URL(link, window.location.href);
+
+ if (url.href === window.location.href) {
+ scrollToTargetLine();
+ } else {
+ window.location.href = link;
+ }
+}
+
function scrollToTargetLine() {
if (!window.location.hash) return;
const target = document.querySelector(window.location.hash);
if (target) {
target.scrollIntoView({ behavior: 'smooth', block: 'start' });
+ restartLineHighlight(target);
}
}
diff --git a/Lib/profiling/sampling/cli.py b/Lib/profiling/sampling/cli.py
index 0648713edc52af..a5d9573ae6b6dd 100644
--- a/Lib/profiling/sampling/cli.py
+++ b/Lib/profiling/sampling/cli.py
@@ -167,7 +167,9 @@ def _build_child_profiler_args(args):
child_args.extend(["--mode", mode])
# Format options (skip pstats as it's the default)
- if args.format != "pstats":
+ if args.format == "diff_flamegraph":
+ child_args.extend(["--diff-flamegraph", args.diff_baseline])
+ elif args.format != "pstats":
child_args.append(f"--{args.format}")
return child_args
diff --git a/Lib/profiling/sampling/stack_collector.py
b/Lib/profiling/sampling/stack_collector.py
index 04622a8c1e89ef..60df026ed76a6c 100644
--- a/Lib/profiling/sampling/stack_collector.py
+++ b/Lib/profiling/sampling/stack_collector.py
@@ -698,6 +698,8 @@ def _add_elided_metadata(self, node, baseline_stats, scale,
path):
func_key = self._extract_func_key(node,
self._baseline_collector._string_table)
current_path = path + (func_key,) if func_key else path
+ baseline_self = 0
+ baseline_total = 0
if func_key and current_path in baseline_stats:
baseline_data = baseline_stats[current_path]
baseline_self = baseline_data["self"] * scale
diff --git a/Lib/test/test_profiling/test_sampling_profiler/test_children.py
b/Lib/test/test_profiling/test_sampling_profiler/test_children.py
index bb49faa890f348..e64d917eedde56 100644
--- a/Lib/test/test_profiling/test_sampling_profiler/test_children.py
+++ b/Lib/test/test_profiling/test_sampling_profiler/test_children.py
@@ -109,6 +109,39 @@ def _wait_for_process_ready(proc, timeout):
return proc.poll() is None
[email protected](
+ _build_child_profiler_args is None,
+ "profiling.sampling.cli unavailable",
+)
+class TestChildProfilerArgBuilder(unittest.TestCase):
+ """Tests for child profiler CLI argument construction."""
+
+ def test_build_child_profiler_args_diff_flamegraph(self):
+ """Test child args use the real --diff-flamegraph flag."""
+ args = argparse.Namespace(
+ sample_interval_usec=1000,
+ duration=None,
+ all_threads=False,
+ realtime_stats=False,
+ native=False,
+ gc=True,
+ opcodes=False,
+ async_aware=False,
+ mode="wall",
+ format="diff_flamegraph",
+ diff_baseline="baseline.bin",
+ )
+
+ child_args = _build_child_profiler_args(args)
+
+ self.assertIn("--diff-flamegraph", child_args)
+ self.assertNotIn("--diff_flamegraph", child_args)
+
+ flag_index = child_args.index("--diff-flamegraph")
+ self.assertGreater(len(child_args), flag_index + 1)
+ self.assertEqual(child_args[flag_index + 1], "baseline.bin")
+
+
@requires_remote_subprocess_debugging()
class TestGetChildPids(unittest.TestCase):
"""Tests for the get_child_pids function."""
diff --git a/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
b/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
index b42e7aa579f40c..390a1479fdd297 100644
--- a/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
+++ b/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
@@ -18,6 +18,7 @@
)
from profiling.sampling.jsonl_collector import JsonlCollector
from profiling.sampling.gecko_collector import GeckoCollector
+ from profiling.sampling.heatmap_collector import _TemplateLoader
from profiling.sampling.collector import extract_lineno, normalize_location
from profiling.sampling.opcode_utils import get_opcode_info, format_opcode
from profiling.sampling.constants import (
@@ -82,6 +83,18 @@ def test_mock_frame_info_with_empty_and_unicode_values(self):
self.assertEqual(frame.location.lineno, 999999)
self.assertEqual(frame.funcname, long_funcname)
+ def test_heatmap_navigation_restarts_line_highlight(self):
+ """Test heatmap navigation can replay target line highlights."""
+ loader = _TemplateLoader()
+
+ self.assertIn(".code-line:target", loader.file_css)
+ self.assertIn("function restartLineHighlight(target)", loader.file_js)
+ self.assertIn("target.style.animation = 'none'", loader.file_js)
+ self.assertIn("void target.offsetWidth", loader.file_js)
+ self.assertIn("url.href === window.location.href", loader.file_js)
+ self.assertIn("navigateToLine(JSON.parse(navData).link)",
loader.file_js)
+ self.assertIn("navigateToLine(linkData.link)", loader.file_js)
+
def test_pstats_collector_with_extreme_intervals_and_empty_data(self):
"""Test PstatsCollector handles zero/large intervals, empty frames,
None thread IDs, and duplicate frames."""
# Test with zero interval
@@ -1403,6 +1416,39 @@ def test_diff_flamegraph_elided_stacks(self):
self.assertGreater(child["baseline"], 0)
self.assertAlmostEqual(child["diff"], -child["baseline"])
+ def test_diff_flamegraph_elided_top_level_root(self):
+ """Elided top-level roots do not crash metadata generation."""
+ baseline_frames_1 = [
+ MockInterpreterInfo(0, [
+ MockThreadInfo(1, [
+ MockFrameInfo("file.py", 10, "kept_leaf"),
+ MockFrameInfo("file.py", 20, "kept_root"),
+ ])
+ ])
+ ]
+ baseline_frames_2 = [
+ MockInterpreterInfo(0, [
+ MockThreadInfo(1, [
+ MockFrameInfo("file.py", 30, "old_leaf"),
+ MockFrameInfo("file.py", 40, "old_root"),
+ ])
+ ])
+ ]
+
+ diff = make_diff_collector_with_mock_baseline([
+ baseline_frames_1,
+ baseline_frames_2,
+ ])
+ diff.collect(baseline_frames_1)
+
+ data = diff._convert_to_flamegraph_format()
+ elided = data["stats"]["elided_flamegraph"]
+ elided_strings = elided.get("strings", [])
+ children = elided.get("children", [])
+
+ self.assertEqual(len(children), 1)
+ self.assertIn("old_root", resolve_name(children[0], elided_strings))
+
def test_diff_flamegraph_function_matched_despite_line_change(self):
"""Functions match by (filename, funcname), ignoring lineno."""
baseline_frames = [
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