tests/cpydiff: Add initial set of tests for uPy-CPython differences.

These tests are intended to fail, as they provide a programatic record of
differences between uPy and CPython.  They also contain a special comment
at the start of the file which has meta-data describing the difference,
including known causes and known workarounds.

tests/cpydiff/core_arguments.py

+"""
+categories: Core
+description: Error messages may display incorrect argument counts
+cause: Unknown
+workaround: Unknown
+"""
+try:
+    [].append()
+except Exception as e:
+    print(e)

tests/cpydiff/core_class_delnotimpl.py

+"""
+categories: Core,Classes
+description: Special method __del__ not implemented for user-defined classes
+cause: Unknown
+workaround: Unknown
+"""
+import gc
+
+class Foo():
+    def __del__(self):
+        print('__del__')
+
+f = Foo()
+del f
+
+gc.collect()

tests/cpydiff/core_class_superaslocal.py

+"""
+categories: Core,Classes
+description: Bug when using "super" as a local
+cause: Unknown
+workaround: Unknown
+"""
+class A:
+    def foo(self):
+        super = [1]
+        super.pop()
+        print(super)
+
+A().foo()

tests/cpydiff/core_class_supermultiple.py

+"""
+categories: Core,Classes
+description: When inheriting from multiple classes super() only calls one class
+cause: Depth first non-exhaustive method resolution order
+workaround: Unknown
+"""
+class A:
+    def __init__(self):
+        print("A.__init__")
+
+class B(A):
+    def __init__(self):
+        print("B.__init__")
+        super().__init__()
+
+class C(A):
+    def __init__(self):
+        print("C.__init__")
+        super().__init__()
+
+
+class D(B,C):
+    def __init__(self):
+        print("D.__init__")
+        super().__init__()
+
+D()

tests/cpydiff/core_class_superproperty.py

+"""
+categories: Core,Classes
+description: Calling super() getter property in subclass will return a property object, not the value
+cause: Unknown
+workaround: Unknown
+"""
+class A:
+    @property
+    def p(self):
+        return {"a":10}
+
+class AA(A):
+    @property
+    def p(self):
+        return super().p
+
+a = AA()
+print(a.p)

tests/cpydiff/core_function_instancevar.py

+"""
+categories: Core,Functions
+description: Assign instance variable to function
+cause: Unknown
+workaround: Unknown
+"""
+def f():
+    pass
+
+f.x = 0
+print(f.x)

tests/cpydiff/core_function_unpacking.py

+"""
+categories: Core,Functions
+description: Unpacking function arguments in non-last position gives incorrect result
+cause: Unknown
+workaround: Unknown
+"""
+print(*(1, 2), 3)

tests/cpydiff/core_generator_noexit.py

+"""
+categories: Core,Generator
+description: Context manager __exit__() not called in a generator which does not run to completion
+cause: Unknown
+workaround: Unknown
+"""
+class foo(object):
+    def __enter__(self):
+        print('Enter')
+    def __exit__(self, *args):
+        print('Exit')
+
+def bar(x):
+    with foo():
+        while True:
+            x += 1
+            yield x
+
+def func():
+    g = bar(0)
+    for _ in range(3):
+        print(next(g))
+
+func()

tests/cpydiff/core_import_prereg.py

+"""
+categories: Core,import
+description: Failed to load modules are still registered as loaded
+cause: Unknown
+workaround: Unknown
+"""
+import sys
+
+try:
+    from modules import foo
+except NameError as e:
+    print(e)
+try:
+    from modules import foo
+    print('Should not get here')
+except NameError as e:
+    print(e)

tests/cpydiff/core_mro.py

+"""
+categories: Core
+description: Method Resolution Order (MRO) is not compliant with CPython
+cause: Unknown
+workaround: Unknown
+"""
+class Foo:
+    def __str__(self):
+        return "Foo"
+
+class C(tuple, Foo):
+    pass
+
+t = C((1, 2, 3))
+print(t)

tests/cpydiff/modules/foo.py

+print('foo')
+xxx

tests/cpydiff/modules_array_containment.py

+"""
+categories: Modules,array
+description: Looking for integer not implemented
+cause: Unknown
+workaround: Unknown
+"""
+import array
+print(1 in array.array('B', b'12'))

tests/cpydiff/modules_array_deletion.py

+"""
+categories: Modules,array
+description: Array deletion not implemented
+cause: Unknown
+workaround: Unknown
+"""
+import array
+a = array.array('b', (1, 2, 3))
+del a[1]
+print(a)

tests/cpydiff/modules_array_subscrstep.py

+"""
+categories: Modules,array
+description: Subscript with step != 1 is not yet implemented
+cause: Unknown
+workaround: Unknown
+"""
+import array
+a = array.array('b', (1, 2, 3))
+print(a[3:2:2])

tests/cpydiff/modules_deque.py

+"""
+categories: Modules,deque
+description: Deque not implemented
+cause: Unknown
+workaround: Use regular queues or lists creatively
+"""
+import collections
+D = collections.deque()
+print(D)

tests/cpydiff/modules_json_nonserializable.py

+"""
+categories: Modules,json
+description: JSON module does not throw exception when object is not serialisable
+cause: Unknown
+workaround: Unknown
+"""
+import json
+a = bytes(x for x in range(256))
+try:
+    z = json.dumps(a)
+    x = json.loads(z)
+    print('Should not get here')
+except TypeError:
+    print('TypeError')

tests/cpydiff/modules_struct_fewargs.py

+"""
+categories: Modules,struct
+description: Struct pack with too few args, not checked by uPy
+cause: Unknown
+workaround: Unknown
+"""
+import struct
+try:
+    print(struct.pack('bb', 1))
+    print('Should not get here')
+except:
+    print('struct.error')

tests/cpydiff/modules_struct_manyargs.py

+"""
+categories: Modules,struct
+description: Struct pack with too many args, not checked by uPy
+cause: Unknown
+workaround: Unknown
+"""
+import struct
+try:
+    print(struct.pack('bb', 1, 2, 3))
+    print('Should not get here')
+except:
+    print('struct.error')

tests/cpydiff/modules_sys_stdassign.py

+"""
+categories: Modules,sys
+description: Override sys.stdin, sys.stdout and sys.stderr. Impossible as they are stored in read-only memory.
+cause: Unknown
+workaround: Unknown
+"""
+import sys
+sys.stdin = None
+print(sys.stdin)