wip

coverage/core.py

@@ -61,6 +61,10 @@ def __init__(self, warn: TWarnFn, config: CoverageConfig, metacov: bool) -> None
                 warn("sys.monitoring isn't available, using default core", slug="no-sysmon")
                 core_name = None
 
+            if core_name == "sysmon" and config.branch and not env.PYBEHAVIOR.branch_taken:
+                warn("sys.monitoring can't yet measure branches well, using default core", slug="no-sysmon")
+                core_name = None
+
             if not core_name:
                 # Once we're comfortable with sysmon as a default:
                 # if env.PYBEHAVIOR.pep669 and self.should_start_context is None:

coverage/env.py

@@ -115,7 +115,7 @@ class PYBEHAVIOR:
     # Does sys.monitoring support BRANCH_TAKEN?
     branch_taken = (
         pep669 and
-        hasattr(sys.monitoring.events, "BRANCH_TAKEN") # type:ignore[attr-defined]
+        hasattr(sys.monitoring.events, "BRANCH_TAKEN") # type:ignore[attr-defined,unused-ignore]
     )
 
 

coverage/sysmon.py

@@ -49,8 +49,8 @@
 if TYPE_CHECKING:
     assert sys_monitoring is not None
     # I want to say this but it's not allowed:
-    #   MonitorReturn = Literal[sys.monitoring.DISABLE] | None
-    MonitorReturn = Any
+    MonitorReturn = Literal[sys.monitoring.DISABLE] | None
+    #MonitorReturn = Any
 
 
 if LOG:  # pragma: debugging
@@ -73,7 +73,10 @@ def _wrapped(*args: Any, **kwargs: Any) -> Any:
     assert sys_monitoring is not None
 
     short_stack = functools.partial(
-        short_stack, full=True, short_filenames=True, frame_ids=True,
+        short_stack,
+        full=True,
+        short_filenames=True,
+        frame_ids=True,
     )
     seen_threads: set[int] = set()
 
@@ -127,7 +130,9 @@ def _wrapped(self: Any, *args: Any) -> Any:
                     return ret
                 except Exception as exc:
                     log(f"!!{exc.__class__.__name__}: {exc}")
-                    log("".join(traceback.format_exception(exc))) # pylint: disable=[no-value-for-parameter]
+                    if 1:
+                        # pylint: disable=no-value-for-parameter
+                        log("".join(traceback.format_exception(exc)))
                     try:
                         assert sys_monitoring is not None
                         sys_monitoring.set_events(sys.monitoring.COVERAGE_ID, 0)
@@ -201,7 +206,6 @@ def __init__(self, tool_id: int) -> None:
         # A list of code_objects, just to keep them alive so that id's are
         # useful as identity.
         self.code_objects: list[CodeType] = []
-        self.last_lines: dict[FrameType, int] = {}
         # Map id(code_object) -> code_object
         self.local_event_codes: dict[int, CodeType] = {}
         self.sysmon_on = False
@@ -346,38 +350,38 @@ def sysmon_py_start(self, code: CodeType, instruction_offset: int) -> MonitorRet
                 with self.lock:
                     if self.sysmon_on:
                         assert sys_monitoring is not None
-                        sys_monitoring.set_local_events(
-                            self.myid,
-                            code,
+                        local_events = (
                             events.PY_RETURN
                             #
                             | events.PY_RESUME
                             # | events.PY_YIELD
                             | events.LINE
-                            | events.BRANCH_TAKEN
-                            | events.BRANCH_NOT_TAKEN
                             # | events.JUMP
                         )
+                        if self.trace_arcs:
+                            assert env.PYBEHAVIOR.branch_taken
+                            local_events |= events.BRANCH_TAKEN | events.BRANCH_NOT_TAKEN
+                        sys_monitoring.set_local_events(self.myid, code, local_events)
                         self.local_event_codes[id(code)] = code
 
-        if tracing_code and self.trace_arcs:
-            frame = self.callers_frame()
-            self.last_lines[frame] = -code.co_firstlineno
-            return None
-        else:
-            return sys.monitoring.DISABLE
+        return sys.monitoring.DISABLE
 
     @panopticon("code", "@")
     def sysmon_py_resume_arcs(
-        self, code: CodeType, instruction_offset: int,
+        self,
+        code: CodeType,
+        instruction_offset: int,
     ) -> MonitorReturn:
         """Handle sys.monitoring.events.PY_RESUME events for branch coverage."""
         frame = self.callers_frame()
         self.last_lines[frame] = frame.f_lineno
 
     @panopticon("code", "@", None)
     def sysmon_py_return_arcs(
-        self, code: CodeType, instruction_offset: int, retval: object,
+        self,
+        code: CodeType,
+        instruction_offset: int,
+        retval: object,
     ) -> MonitorReturn:
         """Handle sys.monitoring.events.PY_RETURN events for branch coverage."""
         frame = self.callers_frame()
@@ -394,7 +398,10 @@ def sysmon_py_return_arcs(
 
     @panopticon("code", "@", "exc")
     def sysmon_py_unwind_arcs(
-        self, code: CodeType, instruction_offset: int, exception: BaseException,
+        self,
+        code: CodeType,
+        instruction_offset: int,
+        exception: BaseException,
     ) -> MonitorReturn:
         """Handle sys.monitoring.events.PY_UNWIND events for branch coverage."""
         frame = self.callers_frame()
@@ -410,7 +417,6 @@ def sysmon_py_unwind_arcs(
                 # log(f"adding {arc=}")
                 cast(Set[TArc], code_info.file_data).add(arc)
 
-
     @panopticon("code", "line")
     def sysmon_line_lines(self, code: CodeType, line_number: int) -> MonitorReturn:
         """Handle sys.monitoring.events.LINE events for line coverage."""

tests/test_concurrency.py

@@ -554,13 +554,19 @@ def test_multiprocessing_with_branching(self, start_method: str) -> None:
         code = (SQUARE_OR_CUBE_WORK + MULTI_CODE).format(NPROCS=nprocs, UPTO=upto)
         total = sum(x*x if x%2 else x*x*x for x in range(upto))
         expected_out = f"{nprocs} pids, total = {total}"
+        expect_warn = (
+            env.PYBEHAVIOR.pep669
+            and (not env.PYBEHAVIOR.branch_taken)
+            and testenv.SYS_MON
+        )
         self.make_file("multi.py", code)
         self.make_file("multi.rc", """\
             [run]
             concurrency = multiprocessing
             branch = True
             omit = */site-packages/*
-            """)
+            """ + ("disable_warnings = no-sysmon" if expect_warn else "")
+            )
 
         out = self.run_command(f"coverage run --rcfile=multi.rc multi.py {start_method}")
         assert out.rstrip() == expected_out