lib.{data,wiring}: add Python 3.14 annotation support.

Author: whitequark

amaranth/lib/data.py

@@ -2,6 +2,10 @@
 from collections.abc import Mapping, Sequence
 import warnings
 import operator
+try:
+    import annotationlib # py3.14+
+except ImportError:
+    annotationlib = None # py3.13-
 
 from amaranth._utils import final
 from amaranth.hdl import *
@@ -1208,22 +1212,29 @@ def __repr__(self):
 
 class _AggregateMeta(ShapeCastable, type):
     def __new__(metacls, name, bases, namespace):
-        if "__annotations__" not in namespace:
+        if "__annotations__" not in namespace and "__annotate_func__" not in namespace:
             # This is a base class without its own layout. It is not shape-castable, and cannot
             # be instantiated. It can be used to share behavior.
             return type.__new__(metacls, name, bases, namespace)
         elif all(not hasattr(base, "_AggregateMeta__layout") for base in bases):
+            annotations = None
+            if annotationlib is not None:
+                if annotate := annotationlib.get_annotate_from_class_namespace(namespace):
+                    annotations = annotationlib.call_annotate_function(
+                        annotate, format=annotationlib.Format.VALUE)
+            if annotations is None:
+                annotations = namespace.get("__annotations__", {})
             # This is a leaf class with its own layout. It is shape-castable and can
             # be instantiated. It can also be subclassed, and used to share layout and behavior.
             layout  = dict()
             default = dict()
-            for field_name in {**namespace["__annotations__"]}:
+            for field_name in {**annotations}:
                 try:
-                    Shape.cast(namespace["__annotations__"][field_name])
+                    Shape.cast(annotations[field_name])
                 except TypeError:
                     # Not a shape-castable annotation; leave as-is.
                     continue
-                layout[field_name] = namespace["__annotations__"].pop(field_name)
+                layout[field_name] = annotations.pop(field_name)
                 if field_name in namespace:
                     default[field_name] = namespace.pop(field_name)
             cls = type.__new__(metacls, name, bases, namespace)

amaranth/lib/wiring.py

@@ -2,6 +2,10 @@
 import enum
 import re
 import warnings
+try:
+    import annotationlib # py3.14+
+except ImportError:
+    annotationlib = None # py3.13-
 
 from .. import tracer
 from ..hdl._ast import Shape, ShapeCastable, Const, Signal, Value
@@ -1669,7 +1673,14 @@ def __init__(self, signature=None, *, src_loc_at=0):
         cls = type(self)
         members = {}
         for base in reversed(cls.mro()[:cls.mro().index(Component)]):
-            for name, annot in base.__dict__.get("__annotations__", {}).items():
+            annotations = None
+            if annotationlib is not None:
+                if annotate := annotationlib.get_annotate_from_class_namespace(base.__dict__):
+                    annotations = annotationlib.call_annotate_function(
+                        annotate, format=annotationlib.Format.VALUE)
+            if annotations is None:
+                annotations = base.__dict__.get("__annotations__", {})
+            for name, annot in annotations.items():
                 if name.startswith("_"):
                     continue
                 if type(annot) is Member:

tests/test_lib_data.py

@@ -1,6 +1,7 @@
 from enum import Enum
+import sys
 import operator
-from unittest import TestCase
+from unittest import TestCase, skipIf
 
 from amaranth.hdl import *
 from amaranth.lib import data
@@ -1312,6 +1313,8 @@ class Sb(data.Struct):
             class Sd(Sb):
                 b: 1
 
+    @skipIf(sys.version_info >= (3, 14),
+        "unclear what the __annotations__ contract is going forward")
     def test_typing_annotation_coexistence(self):
         class S(data.Struct):
             a: unsigned(1)