wip: no stack, works better

coverage/collector.py

@@ -21,6 +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.plugin import CoveragePlugin
 from coverage.pytracer import PyTracer
 from coverage.types import (
@@ -144,17 +145,24 @@ def __init__(
         if HAS_CTRACER and not timid:
             use_ctracer = True
 
-        #if HAS_CTRACER and self._trace_class is CTracer:
-        if use_ctracer:
+        if env.PYBEHAVIOR.pep669 and self.should_start_context is None:
+            self._trace_class = Pep669Tracer
+            self.file_disposition_class = FileDisposition
+            self.supports_plugins = False
+            self.packed_arcs = False
+            self.systrace = False
+        elif use_ctracer:
             self._trace_class = CTracer
             self.file_disposition_class = CFileDisposition
             self.supports_plugins = True
             self.packed_arcs = True
+            self.systrace = True
         else:
             self._trace_class = PyTracer
             self.file_disposition_class = FileDisposition
             self.supports_plugins = False
             self.packed_arcs = False
+            self.systrace = True
 
         # We can handle a few concurrency options here, but only one at a time.
         concurrencies = set(self.concurrency)
@@ -275,6 +283,7 @@ def reset(self) -> None:
 
     def _start_tracer(self) -> TTraceFn:
         """Start a new Tracer object, and store it in self.tracers."""
+        # TODO: for pep669, this doesn't return a TTraceFn
         tracer = self._trace_class()
         tracer.data = self.data
         tracer.trace_arcs = self.branch
@@ -344,7 +353,7 @@ def start(self) -> None:
 
         # Install our installation tracer in threading, to jump-start other
         # threads.
-        if self.threading:
+        if self.systrace and self.threading:
             self.threading.settrace(self._installation_trace)
 
     def stop(self) -> None:

coverage/debug.py

@@ -181,7 +181,7 @@ def exc_one_line(exc: Exception) -> str:
     return "|".join(l.rstrip() for l in lines)
 
 
-def short_stack(limit: Optional[int] = None, skip: int = 0) -> str:
+def short_stack(limit: Optional[int] = None, skip: int = 0, full: bool = False) -> str:
     """Return a string summarizing the call stack.
 
     The string is multi-line, with one line per stack frame. Each line shows
@@ -209,11 +209,12 @@ def short_stack(limit: Optional[int] = None, skip: int = 0) -> str:
     ]
 
     stack: Iterable[inspect.FrameInfo] = inspect.stack()[limit:skip:-1]
-    for pat in BORING_PRELUDE:
-        stack = itertools.dropwhile(
-            (lambda fi, pat=pat: re.search(pat, fi.filename)),  # type: ignore[misc]
-            stack
-        )
+    if not full:
+        for pat in BORING_PRELUDE:
+            stack = itertools.dropwhile(
+                (lambda fi, pat=pat: re.search(pat, fi.filename)),  # type: ignore[misc]
+                stack
+            )
     return "\n".join(f"{fi.function:>30s} : {fi.filename}:{fi.lineno}" for fi in stack)
 
 

coverage/env.py

@@ -113,6 +113,10 @@ class PYBEHAVIOR:
     # Changed in https://github.com/python/cpython/pull/101441
     comprehensions_are_functions = (PYVERSION <= (3, 12, 0, "alpha", 7, 0))
 
+    # PEP669 Low Impact Monitoring: https://peps.python.org/pep-0669/
+    pep669 = bool(getattr(sys, "monitoring", None))
+
+
 # Coverage.py specifics.
 
 # Are we using the C-implemented trace function?