fix: prevent ghost local events in sysmon

python/cpython#111963

Author: nedbat

coverage/collector.py

@@ -21,7 +21,7 @@
 from coverage.disposition import FileDisposition
 from coverage.exceptions import ConfigError
 from coverage.misc import human_sorted_items, isolate_module
-from coverage.pep669_tracer import Pep669Tracer
+from coverage.pep669_monitor import Pep669Monitor
 from coverage.plugin import CoveragePlugin
 from coverage.pytracer import PyTracer
 from coverage.types import (
@@ -130,6 +130,8 @@ def __init__(
         self.concurrency = concurrency
         assert isinstance(self.concurrency, list), f"Expected a list: {self.concurrency!r}"
 
+        self.pid = os.getpid()
+
         self.covdata: CoverageData
         self.threading = None
         self.static_context: Optional[str] = None
@@ -153,7 +155,7 @@ def __init__(
                     core = "ctrace"
 
         if core == "sysmon":
-            self._trace_class = Pep669Tracer
+            self._trace_class = Pep669Monitor
             self.file_disposition_class = FileDisposition
             self.supports_plugins = False
             self.packed_arcs = False
@@ -343,6 +345,11 @@ def _installation_trace(self, frame: FrameType, event: str, arg: Any) -> Optiona
 
     def start(self) -> None:
         """Start collecting trace information."""
+        # We may be a new collector in a forked process.  The old process' 
+        # collectors will be in self._collectors, but they won't be usable.
+        # Find them and discard them.
+        #self.__class__._collectors = [c for c in self._collectors if c.pid == self.pid]
+
         if self._collectors:
             self._collectors[-1].pause()
 
@@ -360,6 +367,10 @@ def start(self) -> None:
         # stack of collectors.
         self._collectors.append(self)
 
+        with open("/tmp/foo.out", "a") as f:
+            print(f"pid={os.getpid()} start: {self._collectors = }", file=f)
+            print(f"start stack:\n{short_stack()}", file=f)
+
         # Install our installation tracer in threading, to jump-start other
         # threads.
         if self.systrace and self.threading:
@@ -380,6 +391,9 @@ def stop(self) -> None:
 
         # Remove this Collector from the stack, and resume the one underneath
         # (if any).
+        with open("/tmp/foo.out", "a") as f:
+            print(f"pid={os.getpid()} stop: {self._collectors = }", file=f)
+            print(f"stop stack:\n{short_stack()}", file=f)
         self._collectors.pop()
         if self._collectors:
             self._collectors[-1].resume()

coverage/control.py

@@ -1,7 +1,7 @@
 # Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
-"""Core control stuff for coverage.py."""
+"""Central control stuff for coverage.py."""
 
 from __future__ import annotations
 

coverage/debug.py

@@ -192,7 +192,7 @@ def short_filename(filename: None) -> None:
     pass
 
 def short_filename(filename: Optional[str]) -> Optional[str]:
-    """shorten a file name. Directories are replaced by prefixes like 'syspath:'"""
+    """Shorten a file name. Directories are replaced by prefixes like 'syspath:'"""
     if not _FILENAME_SUBS:
         for pathdir in sys.path:
             _FILENAME_SUBS.append((pathdir, "syspath:"))

coverage/multiproc.py

@@ -37,7 +37,9 @@ def _bootstrap(self, *args, **kwargs):          # type: ignore[no-untyped-def]
             assert debug is not None
             if debug.should("multiproc"):
                 debug.write("Calling multiprocessing bootstrap")
-        except Exception:
+        except Exception as exc:
+            with open("/tmp/foo.out", "a") as f:
+                print(f"Exception during multiprocessing bootstrap init: {exc.__class__.__name__}: {exc}", file=f)
             print("Exception during multiprocessing bootstrap init:")
             traceback.print_exc(file=sys.stdout)
             sys.stdout.flush()
@@ -47,8 +49,18 @@ def _bootstrap(self, *args, **kwargs):          # type: ignore[no-untyped-def]
         finally:
             if debug.should("multiproc"):
                 debug.write("Finished multiprocessing bootstrap")
-            cov.stop()
-            cov.save()
+            try:
+                cov.stop()
+            except Exception as exc:
+                with open("/tmp/foo.out", "a") as f:
+                    print(f"Exception during multiprocessing bootstrap finally stop: {exc = }", file=f)
+                raise
+            try:
+                cov.save()
+            except Exception as exc:
+                with open("/tmp/foo.out", "a") as f:
+                    print(f"Exception during multiprocessing bootstrap finally save: {exc = }", file=f)
+                raise
             if debug.should("multiproc"):
                 debug.write("Saved multiprocessing data")
 
@@ -86,7 +98,7 @@ def patch_multiprocessing(rcfile: str) -> None:
     # When spawning processes rather than forking them, we have no state in the
     # new process.  We sneak in there with a Stowaway: we stuff one of our own
     # objects into the data that gets pickled and sent to the sub-process. When
-    # the Stowaway is unpickled, it's __setstate__ method is called, which
+    # the Stowaway is unpickled, its __setstate__ method is called, which
     # re-applies the monkey-patch.
     # Windows only spawns, so this is needed to keep Windows working.
     try: