From a28e79f9463c6c227403a13abd9f50fb6715c21a Mon Sep 17 00:00:00 2001
From: "Aryan Singh K." <70511529+aryansk@users.noreply.github.com>
Date: Tue, 18 Aug 2026 16:57:36 +0530
Subject: [PATCH] fix: force trace core when dynamic contexts are requested
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When --cov-context=test is used, force the trace core instead of
sysmon (the default on Python 3.14+) because sysmon does not support
dynamic contexts and coveragepy >= 7.15.3 emits a warning:

    Dynamic contexts aren't supported with core=sysmon; context data
    may be incomplete (no-sysmon-context)

The _coverage_core property returns 'trace' when cov_context == 'test',
and None otherwise (preserving the default core selection). This is
applied to all three Coverage() constructor call sites (Central,
DistMaster, DistWorker).

Fixes #755

🤖 Generated with Codebuff
Co-Authored-By: Codebuff <noreply@codebuff.com>
---
 src/pytest_cov/engine.py | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/pytest_cov/engine.py b/src/pytest_cov/engine.py
index a6a465fa..8db9ecad 100644
--- a/src/pytest_cov/engine.py
+++ b/src/pytest_cov/engine.py
@@ -60,6 +60,7 @@ def __init__(self, options: argparse.Namespace, config: Union[None, object], nod
         self.cov_append = options.cov_append
         self.cov_branch = options.cov_branch
         self.cov_precision = options.cov_precision
+        self.cov_context = getattr(options, 'cov_context', None)
         self.config = config
         self.nodeid = nodeid
 
@@ -72,6 +73,19 @@ def __init__(self, options: argparse.Namespace, config: Union[None, object], nod
         self.is_collocated = None
         self.started = False
 
+    @property
+    def _coverage_core(self):
+        """Return the coverage core to use.
+
+        When dynamic contexts are requested (--cov-context=test),
+        force the ``trace`` core because ``sysmon`` (the default on
+        Python 3.14+) does not support them and coveragepy >= 7.15.3
+        emits a warning.  (#755)
+        """
+        if self.cov_context == 'test':
+            return 'trace'
+        return None
+
     @contextlib.contextmanager
     def ensure_topdir(self):
         original_cwd = Path.cwd()
@@ -234,12 +248,15 @@ class Central(CovController):
 
     @_ensure_topdir
     def start(self):
-        self.cov = coverage.Coverage(
+        cov_kwargs = dict(
             source=self.cov_source,
             branch=self.cov_branch,
             data_suffix=True,
             config_file=self.cov_config,
         )
+        if self._coverage_core is not None:
+            cov_kwargs['core'] = self._coverage_core
+        self.cov = coverage.Coverage(**cov_kwargs)
         if self.cov.config.dynamic_context == 'test_function':
             message = (
                 'Detected dynamic_context=test_function in coverage configuration. '
@@ -284,12 +301,15 @@ class DistMaster(CovController):
 
     @_ensure_topdir
     def start(self):
-        self.cov = coverage.Coverage(
+        cov_kwargs = dict(
             source=self.cov_source,
             branch=self.cov_branch,
             data_suffix=True,
             config_file=self.cov_config,
         )
+        if self._coverage_core is not None:
+            cov_kwargs['core'] = self._coverage_core
+        self.cov = coverage.Coverage(**cov_kwargs)
         if self.cov.config.dynamic_context == 'test_function':
             raise DistCovError(
                 'Detected dynamic_context=test_function in coverage configuration. '
@@ -387,12 +407,15 @@ def start(self):
             self.cov_config = self.cov_config.replace(master_topdir, worker_topdir)
 
         # Erase any previous data and start coverage.
-        self.cov = coverage.Coverage(
+        cov_kwargs = dict(
             source=self.cov_source,
             branch=self.cov_branch,
             data_suffix=True,
             config_file=self.cov_config,
         )
+        if self._coverage_core is not None:
+            cov_kwargs['core'] = self._coverage_core
+        self.cov = coverage.Coverage(**cov_kwargs)
         # Prevent workers from issuing module-not-measured type of warnings (expected for a workers to not have coverage in all the files).
         self.cov._warn_unimported_source = False
         self.cov.start()