tests/cpydiff/core_class: Document limitations of __init_subclass__.

AJMansfield · AJMansfield · commit aebeeb840341 · 2024-07-20T11:32:56.000-04:00
Signed-off-by: Anson Mansfield &lt;amansfield@mantaro.com&gt;
diff --git a/tests/cpydiff/core_class_initsubclass_kw.py b/tests/cpydiff/core_class_initsubclass_kw.py
@@ -0,0 +1,19 @@
+"""
+categories: Core,Classes
+description: Keyword arguments are not passed to __init_subclass__.
+cause: Micropython doesn't allow kwargs in a base class list.
+workaround: Unknown
+"""
+
+
+class Philosopher:
+    def __init_subclass__(cls, default_name, **kwargs):
+        super().__init_subclass__(**kwargs)
+        cls.default_name = default_name
+
+
+class AustralianPhilosopher(Philosopher, default_name="Bruce"):
+    pass
+
+
+print(AustralianPhilosopher.default_name)
diff --git a/tests/cpydiff/core_class_initsubclass_multi.py b/tests/cpydiff/core_class_initsubclass_multi.py
@@ -0,0 +1,77 @@
+"""
+categories: Core,Classes
+description: Micropython calls __init_subclass__ directly for all direct base classes.
+cause: Micropython can't rely on __init_subclass__ implementations calling super().__init_subclass__() to recurse through ancestor classes like CPython.
+workaround: Omit calling super().__init_subclass__() in __init_subclass__ implementations.
+"""
+
+
+# In CPython, only the first base__init_subclass__
+class A1:
+    a = "A1"
+
+    def __init_subclass__(cls):
+        print("A1 init_subclass", cls.__name__)
+        cls.aa = "AA"
+
+    print("class A1")
+
+
+class B1:
+    b = "B1"
+
+    def __init_subclass__(cls):
+        print("B1 init_subclass", cls.__name__)
+        cls.bb = "BB"
+
+    print("class B1")
+
+
+class C1(A1, B1):
+    c = "C1"
+    print("class C1")
+
+
+# In CPython it's specified to call super().__init_subclass__() in __init_subclass__.
+# But the presence of super() makes the invocation of __init_subclass__ fail.
+class A2:
+    a = "A2"
+
+    @classmethod
+    def __init_subclass__(cls):
+        super().__init_subclass__()
+        print("A2 init_subclass", cls.__name__)
+        cls.aa = "AA"
+
+    print("class A2")
+
+
+class B2:
+    b = "B2"
+
+    @classmethod
+    def __init_subclass__(cls):
+        super().__init_subclass__()
+        print("B2 init_subclass", cls.__name__)
+        cls.bb = "BB"
+
+    print("class B2")
+
+
+class C2(A2, B2):
+    c = "C2"
+    print("class C2")
+
+
+def print_check_all_attrs(obj, name: str, attrs: "list[str]"):
+    for attr in attrs:
+        print(name, attr, getattr(obj, attr, "missing"))
+
+
+print_check_all_attrs(A1, "A1", ["a", "aa", "b", "bb", "c"])
+print_check_all_attrs(B1, "B1", ["a", "aa", "b", "bb", "c"])
+print_check_all_attrs(C1, "C1", ["a", "aa", "b", "bb", "c"])
+
+print_check_all_attrs(A2, "A2", ["a", "aa", "b", "bb", "c"])
+print_check_all_attrs(B2, "B2", ["a", "aa", "b", "bb", "c"])
+print_check_all_attrs(C2, "C2", ["a", "aa", "b", "bb", "c"])
diff --git a/tests/cpydiff/core_class_initsubclass_recursive.py b/tests/cpydiff/core_class_initsubclass_recursive.py
@@ -0,0 +1,42 @@
+"""
+categories: Core,Classes
+description: Micropython can't recurse through base classes for __init_subclass__.
+cause: Micropython doesn't support super() inside classmethods.
+workaround: Unknown
+"""
+
+
+class A:
+    a = "A"
+
+    def __init_subclass__(cls):
+        print("A init_subclass", cls.__name__)
+        cls.aa = "AA"
+
+    print("class A")
+
+
+class B(A):
+    b = "B"
+
+    def __init_subclass__(cls):
+        super().__init_subclass__()
+        print("B init_subclass", cls.__name__)
+        cls.bb = "BB"
+
+    print("class B")
+
+
+class C(B):
+    c = "C"
+    print("class C")
+
+
+def print_check_all_attrs(obj, name: str, attrs: "list[str]"):
+    for attr in attrs:
+        print(name, attr, getattr(obj, attr, "missing"))
+
+
+print_check_all_attrs(A, "A", ["a", "aa", "b", "bb", "c"])
+print_check_all_attrs(B, "B", ["a", "aa", "b", "bb", "c"])
+print_check_all_attrs(C, "C", ["a", "aa", "b", "bb", "c"])
