fix: revert an illusory performance gain that broke debuggers. #1420

Author: nedbat

CHANGES.rst

@@ -27,10 +27,17 @@ Unreleased
   constructs) could cause incorrect claims of missing branches with the
   sys.monitoring core, as described in `issue 2070`_. This is now fixed.
 
+- Fix: when running in pytest under coverage, a ``breakpoint()`` would stop in
+  the wrong frame, one level down from where it should, as described in `issue
+  1420`_. This was due to a coverage change in v6.4.1 that seemed to give a
+  slight performance improvement, but I couldn't reproduce the performance
+  gain, so it's been reverted, fixing the debugger problem.
+
 - Split ``sqlite`` debugging information out of the ``sys`` :ref:`coverage
   debug <cmd_debug>` and :ref:`cmd_run_debug` options since it's bulky and not
   very useful.
 
+.. _issue 1420: https://github.com/nedbat/coveragepy/issues/1420
 .. _issue 2070: https://github.com/nedbat/coveragepy/issues/2070
 
 

coverage/ctracer/tracer.c

@@ -545,7 +545,6 @@ CTracer_handle_call(CTracer *self, PyFrameObject *frame)
         Py_XDECREF(self->pcur_entry->file_data);
         self->pcur_entry->file_data = NULL;
         self->pcur_entry->file_tracer = Py_None;
-        MyFrame_NoTraceLines(frame);
         SHOWLOG(PyFrame_GetLineNumber(frame), filename, "skipped");
     }
 

coverage/ctracer/util.h

@@ -33,10 +33,8 @@
 #endif
 
 #if PY_VERSION_HEX >= 0x030D0000
-#define MyFrame_NoTraceLines(f) (PyObject_SetAttrString((PyObject*)(f), "f_trace_lines", Py_False))
 #define MyFrame_SetTrace(f, obj)    (PyObject_SetAttrString((PyObject*)(f), "f_trace", (PyObject*)(obj)))
 #else
-#define MyFrame_NoTraceLines(f) ((f)->f_trace_lines = 0)
 #define MyFrame_SetTrace(f, obj)    {Py_INCREF(obj); Py_XSETREF((f)->f_trace, (PyObject*)(obj));}
 #endif