WIP: L2SS-938: add coverage trace wrapper

Closes L2SS-938

tangostationcontrol/tangostationcontrol/common/coverage.py

+# Copyright (C) 2022 ASTRON (Netherlands Institute for Radio Astronomy)
+# SPDX-License-Identifier: Apache-2.0
+
+# Code coverage tools 'coverage' and 'pytest-cov' don't seem to correctly trace
+# code which is inside methods called from within QThreads, see
+# https://github.com/nedbat/coveragepy/issues/686
+# To mitigate this problem, I use a custom decorator '@coverage_resolve_trace'
+# to be hung onto those method definitions. This will prepend the decorated
+# method code with 'sys.settrace(threading._trace_hook)' when a code
+# coverage test is detected. When no coverage test is detected, it will just
+# pass the original method untouched.
+import sys
+import threading
+from functools import wraps
+
+__all__ = ["coverage_resolve_trace"]
+
+
+def coverage_resolve_trace(fn):
+    """Wrapper to trace code coverage in Tango devices"""
+
+    @wraps(fn)
+    def wrapped(*args, **kwargs):
+        if "coverage" in sys.modules:
+            sys.settrace(threading._trace_hook)
+        return fn(*args, **kwargs)
+
+    return wrapped