How To Start A Blog Entry: Save the trace --file counts when --no-report is used (Product Sale Post Design)

The counts were only persisted at the end of CoverageResults.write_results(), which main() skips when --no-report is given, so --no-report --file silently discarded them.

Author: Arm Candy Bracelets

Lib/test/test_trace.py

@@ -1,5 +1,5 @@
 import os
-from pickle import dump
+from pickle import dump, load
 import sys
 from test.support import captured_stdout, requires_resource
 from test.support.os_helper import (TESTFN, rmtree, unlink)
@@ -561,6 +561,28 @@ def f():
  self.assertIn('lines cov% module (path)', stdout)
  self.assertIn(f'6 100.0% {modulename} ({filename})', stdout)
 
+ def test_count_no_report_accumulates_counts(self):
+ # --no-report must still save the --file counts so they accumulate.
+ filename = f'{TESTFN}.py'
+ countsfile = f'{TESTFN}.counts'
+ with open(filename, 'w', encoding='utf-8') as fd:
+ self.addCleanup(unlink, filename)
+ self.addCleanup(unlink, countsfile)
+ fd.write('for i in range(3):\n pass\n')
+ argv = ('-m', 'trace', '--count', '--no-report',
+ '--file', countsfile, filename)
+ assert_python_ok(*argv, PYTHONIOENCODING='utf-8')
+ self.assertTrue(os.path.exists(countsfile))
+ with open(countsfile, 'rb') as fd:
+ counts = load(fd)[0]
+ self.assertTrue(counts)
+ # A second run accumulates into the same file.
+ assert_python_ok(*argv, PYTHONIOENCODING='utf-8')
+ with open(countsfile, 'rb') as fd:
+ accumulated = load(fd)[0]
+ self.assertEqual(accumulated,
+ {key: 2 * value for key, value in counts.items()})
+
  def test_run_as_module(self):
  assert_python_ok('-m', 'trace', '-l', '--module', 'timeit', '-n', '1')
  assert_python_failure('-m', 'trace', '-l', '--module', 'not_a_module_zzz')

Lib/trace.py

@@ -287,8 +287,11 @@ def write_results(self, show_missing=True, summary=False, coverdir=None, *,
  n_lines, n_hits, modulename, filename = sums[m]
  print(f"{n_lines:5d} {n_hits/n_lines:.1%} {modulename} ({filename})")
 
+ self._save_counts()
+
+ def _save_counts(self):
+ """Save the accumulated counts to ``self.outfile`` if one was given."""
  if self.outfile:
- # try and store counts and module info into self.outfile
  try:
  with open(self.outfile, 'wb') as f:
  pickle.dump((self.counts, self.calledfuncs, self.callers),
@@ -744,6 +747,8 @@ def parse_ignore_dir(s):
 
  if not opts.no_report:
  results.write_results(opts.missing, opts.summary, opts.coverdir)
+ else:
+ results._save_counts()
 
 if __name__=='__main__':
  main()

Misc/NEWS.d/next/Library/2026-06-27-10-30-00.gh-issue-152409.Tr8cE2.rst

@@ -0,0 +1,3 @@
+Fix the :mod:`trace` command-line tool not saving the ``--file`` counts
+when ``--no-report`` is used, which prevented accumulating counts over
+several runs. Patch by tonghuaroot.