Allow forward-references on 3.14 (#1451)

* Request stringified annotations

* Add test

* ruff: mark test_forward_references as 3.14

* Use FORWARDREF instead

See
https://github.com/python/cpython/blob/9d3b53c47fab9ebf1f40d6f21b7d1ad391c14cd7/Lib/dataclasses.py#L989-L990

* Fix comment

* Apply docstring standard

* Add news fragment

Unite with the other one to avoid confusion.

* Temporal form

* Flesh out test

---------

Co-authored-by: Hynek Schlawack <[email protected]>

Author: Tinche

changelog.d/1446.change.md

@@ -1,2 +1 @@
-On 3.14, the cycles in slotted classes are now manually broken.
-An explicit call to `gc.collect()` is still necessary, unfortunately.
+Added support for Python 3.14.

changelog.d/1451.change.md

@@ -0,0 +1 @@
+Added support for Python 3.14.

pyproject.toml

@@ -196,6 +196,7 @@ line-length = 79
 
 [tool.ruff.per-file-target-version]
 "tests/test_pattern_matching.py" = "py310"
+"tests/test_forward_references.py" = "py314"
 
 [tool.ruff.lint]
 select = ["ALL"]

src/attr/_compat.py

@@ -17,10 +17,16 @@
 PY_3_14_PLUS = sys.version_info[:2] >= (3, 14)
 
 
-if PY_3_14_PLUS:  # pragma: no cover
+if PY_3_14_PLUS:
     import annotationlib
 
-    _get_annotations = annotationlib.get_annotations
+    # We request forward-ref annotations to not break in the presence of
+    # forward references.
+
+    def _get_annotations(cls):
+        return annotationlib.get_annotations(
+            cls, format=annotationlib.Format.FORWARDREF
+        )
 
 else:
 

conftest.py renamed to tests/conftest.py

@@ -6,7 +6,7 @@
 
 from hypothesis import HealthCheck, settings
 
-from attr._compat import PY_3_10_PLUS
+from attr._compat import PY_3_10_PLUS, PY_3_14_PLUS
 
 
 @pytest.fixture(name="slots", params=(True, False))
@@ -33,4 +33,6 @@ def pytest_configure(config):
 
 collect_ignore = []
 if not PY_3_10_PLUS:
-    collect_ignore.extend(["tests/test_pattern_matching.py"])
+    collect_ignore.extend(["test_pattern_matching.py"])
+if not PY_3_14_PLUS:
+    collect_ignore.extend(["test_forward_references.py"])

tests/test_forward_references.py

@@ -0,0 +1,22 @@
+"""
+Tests for behavior specific to forward references via PEP 749.
+"""
+
+from attrs import define, fields, resolve_types
+
+
+def test_forward_class_reference():
+    """
+    Class A can reference B even though it is defined later.
+    """
+
+    @define
+    class A:
+        b: B
+
+    class B:
+        pass
+
+    resolve_types(A)
+
+    assert fields(A).b.type is B