Fix flaky coverage for Pandas

Author: Zac-HD

hypothesis-python/src/hypothesis/internal/coverage.py

@@ -48,6 +48,7 @@ def pretty_file_name(f):
 
 
 IN_COVERAGE_TESTS = os.getenv("HYPOTHESIS_INTERNAL_COVERAGE") == "true"
+description_stack = []
 
 
 if IN_COVERAGE_TESTS:
@@ -64,8 +65,6 @@ def record_branch(name, value):
         with open(f"branch-check-{os.getpid()}", mode="a", encoding="utf-8") as log:
             log.write(json.dumps({"name": name, "value": value}) + "\n")
 
-    description_stack = []
-
     @contextmanager
     def check_block(name, depth):
         # We add an extra two callers to the stack: One for the contextmanager

hypothesis-python/src/hypothesis/strategies/_internal/core.py

@@ -83,6 +83,7 @@
     is_typed_named_tuple,
 )
 from hypothesis.internal.conjecture.utils import calc_label_from_cls, check_sample
+from hypothesis.internal.coverage import IN_COVERAGE_TESTS, description_stack
 from hypothesis.internal.entropy import get_seeder_and_restorer
 from hypothesis.internal.floats import float_of
 from hypothesis.internal.observability import TESTCASE_CALLBACKS
@@ -1757,8 +1758,22 @@ def __init__(self, definition, args, kwargs):
         self.args = args
         self.kwargs = kwargs
 
-    def do_draw(self, data):
-        return self.definition(data.draw, *self.args, **self.kwargs)
+    if IN_COVERAGE_TESTS:
+        # We do a bit of a dance here to ensure that whatever 'outer' description
+        # stack we might have, doesn't affect the validation code internal to the
+        # strategy we're drawing from.  Otherwise, we'd get flaky fails like #3968.
+        def do_draw(self, data):
+            prev = description_stack[:]
+            try:
+                description_stack.clear()
+                return self.definition(data.draw, *self.args, **self.kwargs)
+            finally:
+                description_stack[:] = prev
+
+    else:  # pragma: no cover
+
+        def do_draw(self, data):
+            return self.definition(data.draw, *self.args, **self.kwargs)
 
     def calc_label(self):
         return calc_label_from_cls(self.definition)