gh-110722: Make `-m test -T -j` use sys.monitoring (GH-111710)

Now all results from worker processes are aggregated and
displayed together as a summary at the end of a regrtest run.

The traditional trace is left in place for use with sequential
in-process test runs but now raises a warning that those
numbers are not precise.

`-T -j` requires `--with-pydebug` as it relies on `-Xpresite=`.

1 files changed, 8 insertions, 2 deletions

diff --git a/Lib/trace.py b/Lib/trace.py
index fb9a423..7cb6f89 100755
--- a/Lib/trace.py
+++ b/Lib/trace.py
@@ -202,7 +202,8 @@ class CoverageResults:
         for key in other_callers:
             callers[key] = 1
 
-    def write_results(self, show_missing=True, summary=False, coverdir=None):
+    def write_results(self, show_missing=True, summary=False, coverdir=None, *,
+                      ignore_missing_files=False):
         """
         Write the coverage results.
 
@@ -211,6 +212,9 @@ class CoverageResults:
         :param coverdir: If None, the results of each module are placed in its
                          directory, otherwise it is included in the directory
                          specified.
+        :param ignore_missing_files: If True, counts for files that no longer
+                         exist are silently ignored. Otherwise, a missing file
+                         will raise a FileNotFoundError.
         """
         if self.calledfuncs:
             print()
@@ -253,6 +257,9 @@ class CoverageResults:
             if filename.endswith(".pyc"):
                 filename = filename[:-1]
 
+            if ignore_missing_files and not os.path.isfile(filename):
+                continue
+
             if coverdir is None:
                 dir = os.path.dirname(os.path.abspath(filename))
                 modulename = _modname(filename)
@@ -278,7 +285,6 @@ class CoverageResults:
                 percent = int(100 * n_hits / n_lines)
                 sums[modulename] = n_lines, percent, modulename, filename
 
-
         if summary and sums:
             print("lines   cov%   module   (path)")
             for m in sorted(sums):