don't run metacov on 3.12/3.13 sysmon since it can't do branches

Author: nedbat

igor.py

@@ -126,14 +126,17 @@ def label_for_core(core):
         raise ValueError(f"Bad core: {core!r}")
 
 
-def should_skip(core):
+def should_skip(core, metacov):
     """Is there a reason to skip these tests?
 
     Return empty string to run tests, or a message about why we are skipping
     the tests.
     """
     skipper = ""
 
+    if metacov and core == "sysmon" and ((3, 12) <= sys.version_info < (3, 14)):
+        skipper = "sysmon can't measure branches in Python 3.12-3.13"
+
     # $set_env.py: COVERAGE_TEST_CORES - List of cores to run: ctrace, pytrace, sysmon
     test_cores = os.getenv("COVERAGE_TEST_CORES")
     if test_cores:
@@ -154,7 +157,8 @@ def should_skip(core):
                     skipper = f"No C core for {platform.python_implementation()}"
 
     if skipper:
-        return f"Skipping tests {label_for_core(core)}: {skipper}"
+        what = "metacov" if metacov else "tests"
+        return f"Skipping {what} {label_for_core(core)}: {skipper}"
     else:
         return ""
 
@@ -226,11 +230,6 @@ def run_tests_with_coverage(core, *runner_args):
                     del sys.modules[name]
         remove_extension(core)
 
-        # Remove the reference to metacov.ini.
-        del os.environ["COVERAGE_PROCESS_START"]
-        os.environ["COVERAGE_DEBUG"] = "sys,config,trace"
-        os.environ["COVERAGE_DEBUG_FILE"] = "/tmp/foo.out"
-
         import coverage  # pylint: disable=reimported
 
         sys.modules.update(covmods)
@@ -268,15 +267,17 @@ def do_combine_html():
 
 def do_test_with_core(core, *runner_args):
     """Run tests with a particular core."""
+    metacov = os.getenv("COVERAGE_COVERAGE", "no") == "yes"
+
     # If we should skip these tests, skip them.
-    skip_msg = should_skip(core)
+    skip_msg = should_skip(core, metacov)
     if skip_msg:
         if VERBOSITY > 0:
             print(skip_msg)
         return None
 
     os.environ["COVERAGE_CORE"] = core
-    if os.getenv("COVERAGE_COVERAGE", "no") == "yes":
+    if metacov:
         return run_tests_with_coverage(core, *runner_args)
     else:
         return run_tests(core, *runner_args)