fix: ignore deferred annotation code. #1908

Author: nedbat

CHANGES.rst

@@ -23,12 +23,19 @@ upgrading your version of coverage.py.
 Unreleased
 ----------
 
+- Fix: Python 3.14 `defers evaluation of annotations <pep649_>`_ by moving them
+  into separate code objects.  That code is rarely executed, so coverage.py
+  would mark them as missing, as reported in `issue 1908`_.  Now they are
+  ignored by coverage automatically.
+
 - Fixed an obscure and mysterious problem on PyPy 3.10 seemingly involving
   mocks, imports, and trace functions: `issue 1902`_.  To be honest, I don't
   understand the problem or the solution, but ``git bisect`` helped find it,
   and now it's fixed.
 
 .. _issue 1902: https://github.com/nedbat/coveragepy/issues/1902
+.. _issue 1908: https://github.com/nedbat/coveragepy/issues/1908
+.. _pep649: https://docs.python.org/3.14/whatsnew/3.14.html#pep-649-deferred-evaluation-of-annotations
 
 
 .. start-releases

coverage/env.py

@@ -100,6 +100,9 @@ class PYBEHAVIOR:
     # https://github.com/python/cpython/issues/113728
     lasti_is_yield = (PYVERSION[:2] != (3, 13))
 
+    # PEP649 and PEP749: Deferred annotations
+    deferred_annotations = (PYVERSION >= (3, 14))
+
 
 # Coverage.py specifics, about testing scenarios. See tests/testenv.py also.
 

coverage/parser.py

@@ -413,8 +413,17 @@ def child_parsers(self) -> Iterable[ByteParser]:
 
         The iteration includes `self` as its first value.
 
+        We skip code objects named `__annotate__` since they are deferred
+        annotations that usually are never run.  If there are errors in the
+        annotations, they will be caught by type checkers or other tools that
+        use annotations.
+
         """
-        return (ByteParser(self.text, code=c) for c in code_objects(self.code))
+        return (
+            ByteParser(self.text, code=c)
+            for c in code_objects(self.code)
+            if c.co_name != "__annotate__"
+        )
 
     def _line_numbers(self) -> Iterable[TLineNo]:
         """Yield the line numbers possible in this code object.

tests/test_coverage.py

@@ -1290,6 +1290,35 @@ def foo(self):
         )
 
 
+class AnnotationTest(CoverageTest):
+    """Tests specific to annotations."""
+
+    def test_attribute_annotation(self) -> None:
+        if env.PYBEHAVIOR.deferred_annotations:
+            lines = [1, 3]
+        else:
+            lines = [1, 2, 3]
+        self.check_coverage("""\
+            class X:
+                x: int
+                y = 1
+            """,
+            lines=lines,
+            missing="",
+        )
+
+    def test_attribute_annotation_from_future(self) -> None:
+        self.check_coverage("""\
+            from __future__ import annotations
+            class X:
+                x: int
+                y = 1
+            """,
+            lines=[1, 2, 3, 4],
+            missing="",
+        )
+
+
 class ExcludeTest(CoverageTest):
     """Tests of the exclusion feature to mark lines as not covered."""