Merge branch 'release-0.2.2'

CHANGES.md

@@ -1,5 +1,12 @@
 # Release notes
 
+## 0.2.2 (2016-05-15)
+
+- fields with default values are properly passed to __new__()/__init__()
+- added support for coercion of tuples for Struct-typed fields
+- added support for `__getitem__` and `__setitem__`
+- testing a Struct for equality with itself succeeds quickly
+
 ## 0.2.1 (2014-12-20)
 
 - changed type checking keyword argument names: `opt` -> `or_none`

CONTRIBUTORS.md

@@ -0,0 +1,2 @@
+- Jon Brandvein - Author, maintainer
+- Bo Lin - Struct indexing, tuple coercion for Struct-typed fields

LICENSE

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2013-2014 Jonathan Brandvein
+Copyright (c) 2013-2015 Jonathan Brandvein
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the "Software"), to deal in

README.md

@@ -1,4 +1,4 @@
-# SimpleStruct
+# SimpleStruct #
 
 *(Supports Python 3.3 and up)*
 
@@ -9,7 +9,7 @@ inheritance-based approach instead of `eval()`ing a code template. If
 you like using `namedtuple` classes but wish they were more composable
 and extensible, this project is for you.
 
-## Example
+## Example ##
 
 Writing struct classes by hand is tedious and error prone. Consider a
 simple point class. The bare minimum we can write in Python is
@@ -93,7 +93,7 @@ File | Purpose
 [vector.py](examples/vector.py) | advanced features
 [abstract.py](examples/abstract.py) | mixing structs and metaclasses
 
-## Comparison and feature matrix
+## Comparison and feature matrix ##
 
 The most important problems mentioned above are solved by using
 `namedtuple`, but this approach begins to break down when you
@@ -114,7 +114,7 @@ the boilerplate methods so they recognize the new fields. This can be
 done using multiple inheritance:
 
 ```python
-BaseEmployee = namedtuple('BaseEmployee', Employee._fields + ('salary',))
+BaseEmployee = namedtuple('BaseEmployee', BasePerson._fields + ('salary',))
 class Employee(BaseEmployee, Person):
     pass
 ```
@@ -138,16 +138,17 @@ optional mutability | | ✗
 hashing (if immutable) | `__hash__()` | ✓
 pickling / deep-copying |  | ✓
 tuple decomposition | `__len__`, `__iter__` | ✓
+indexing | `__getitem__`, `__setitem__` | `__getitem__` only
 optional type checking | `__init__()`, `@property` | ✗
 `_asdict()` / `_replace()` | | ✓
 
-[MacroPy][2]'s case classes provide similar functionality, but is
+[MacroPy][2]'s "case classes" provide similar functionality, but are
 implemented in a very different way. Instead of metaclass hacking
-or source code templating, it relies on syntactic transformation
+or source code templating, MacroPy relies on syntactic transformation
 of the module's AST. This allows for a syntax that's very different
 from what we've seen above. So different, in fact, that we might view
 MacroPy as an extension to the Python language rather than as just
-a library. MacroPy case classes are subject to limitations on
+a library. Case classes are subject to limitations on
 inheritance and class members.
 
 ## Installation ##

TODO.md

@@ -1,3 +1,19 @@
+# Bugs #
+- equality testing of cyclic objects can cause infinite recursion.
+
+```python
+class A(Struct):
+    x = Field()
+a1 = A(None)
+a2 = A(None)
+a1.x = a2
+a2.x = a1
+a1 == a2
+```
+The proper behavior in this case should probably be to allow `a1 == a2`
+to return `False` for simplicity, even though `a1` and `a2` are actually
+isomorphic.
+
 # Wishlist #
 - add support for `__slots__`
 - make exceptions appear to be raised from the stack frame of user code

examples/typed.py

@@ -108,3 +108,14 @@ class NullablePoint(Struct):
     z = myfield
 
 p = NullablePoint(1, 2.0, None)
+
+
+# Struct-typed fields can be coerced from tuple values.
+
+class Line(Struct):
+    a = TypedField(TypedPoint)
+    b = TypedField(TypedPoint)
+
+line1 = Line(TypedPoint(1, 2), TypedPoint(3, 4))
+line2 = Line((1, 2), (3, 4))
+assert line1 == line2

examples/vector.py

@@ -83,18 +83,19 @@ class MutablePoint(Struct):
 # The arguments are the declared fields, in order of their declaration.
 #
 # Fields are initialized in __new__(). A subclass that overrides
-# __new__() must call super.__new__() (not type.__new__()).
+# __new__() must call super().__new__() (not type.__new__()).
 # __init__() does not need to call super().__init__() or do any work
 # on behalf of the Struct system.
 #
 # If the fields have default values, these are substituted in before
 # calling the constructor. Thus providing default parameter values
-# in the constructor argument list is meaningless.
+# in the constructor argument list is meaningless, as they will always
+# be overridden by the defaults from the field's declaration.
 
 class DoublingVector2D(Struct):
 
-    x = Field
-    y = Field
+    x = Field(default=0)
+    y = Field(default=0)
 
     def __new__(cls, x, y):
         print('Vector2D.__new__() has been called')

setup.py

@@ -2,7 +2,7 @@
 
 setup(
     name =          'SimpleStruct',
-    version =       '0.2.1',
+    version =       '0.2.2',
     url =           '/~https://github.com/brandjon/simplestruct',
 
     author =        'Jon Brandvein',

simplestruct/__init__.py

@@ -3,7 +3,7 @@
 checking, mutability, and inheritance.
 """
 
-__version__ = '0.2.1'
+__version__ = '0.2.2'
 
 from .struct import *
 from .fields import *

simplestruct/fields.py

@@ -6,7 +6,7 @@
 ]
 
 
-from .struct import Field
+from .struct import Field, Struct
 from .type import TypeChecker
 
 
@@ -22,6 +22,9 @@ class TypedField(Field, TypeChecker):
     determined by kind.__eq__()).
     
     If or_none is True, None is a valid value.
+    
+    If the kind is a Struct and seq is False, allow the value to
+    be a tuple and coerce it to an instance of the Struct.
     """
 
     def __init__(self, kind, *,
@@ -64,6 +67,15 @@ def normalize(self, inst, value):
         return value
 
     def __set__(self, inst, value):
+        # Special case: If our type is a non-sequence Struct, allow
+        # coercion of a tuple value to the Struct. This is done
+        # prior to the type check and normalization.
+        if (not self.seq and len(self.kind) == 1 and
+                isinstance(self.kind[0], type) and
+                issubclass(self.kind[0], Struct) and
+                isinstance(value, tuple)):
+            value = self.kind[0](*value)
+
         self.check(inst, value)
         value = self.normalize(inst, value)
         super().__set__(inst, value)

simplestruct/struct.py

@@ -95,11 +95,12 @@ class MetaStruct(type):
     
     Upon instantiation of a Struct subtype, set the instance's
     _initialized attribute to True after __init__() returns.
+    Preprocess its __new__/__init__() arguments as well.
     """
 
     # Use OrderedDict to preserve Field declaration order.
     @classmethod
-    def __prepare__(mcls, name, bases, **kargs):
+    def __prepare__(cls, name, bases, **kargs):
         return OrderedDict()
 
     # Construct the _struct attribute on the new class.
@@ -144,9 +145,23 @@ def __new__(mcls, clsname, bases, namespace, **kargs):
 
         return cls
 
+    def get_boundargs(cls, *args, **kargs):
+        """Return an inspect.BoundArguments object for the application
+        of this Struct's signature to its arguments. Add missing values
+        for default fields as keyword arguments.
+        """
+        boundargs = cls._signature.bind(*args, **kargs)
+        # Include default arguments.
+        for param in cls._signature.parameters.values():
+            if (param.name not in boundargs.arguments and
+                param.default is not param.empty):
+                boundargs.arguments[param.name] = param.default
+        return boundargs
+
     # Mark the class as _initialized after construction.
-    def __call__(mcls, *args, **kargs):
-        inst = super().__call__(*args, **kargs)
+    def __call__(cls, *args, **kargs):
+        boundargs = cls.get_boundargs(*args, **kargs)
+        inst = super().__call__(*boundargs.args, **boundargs.kwargs)
         inst._initialized = True
         return inst
 
@@ -193,12 +208,7 @@ def __new__(cls, *args, **kargs):
 
         f = None
         try:
-            boundargs = cls._signature.bind(*args, **kargs)
-            # Include default arguments.
-            for param in cls._signature.parameters.values():
-                if (param.name not in boundargs.arguments and
-                    param.default is not param.empty):
-                    boundargs.arguments[param.name] = param.default
+            boundargs = cls.get_boundargs(*args, **kargs)
             for f in cls._struct:
                 setattr(inst, f.name, boundargs.arguments[f.name])
             f = None
@@ -231,6 +241,13 @@ def __repr__(self):
         return self._fmt_helper(repr)
 
     def __eq__(self, other):
+        # Succeed immediately if we're being tested against ourselves
+        # (identical object in memory). This avoids an unnecessary
+        # walk over the fields, which can be expensive if the field
+        # values are themselves Structs, and so on.
+        if self is other:
+            return True
+
         # Two struct instances are equal if they have the same
         # type and same field values.
         if type(self) != type(other):
@@ -257,6 +274,26 @@ def __len__(self):
     def __iter__(self):
         return (getattr(self, f.name) for f in self._struct)
 
+    def __getitem__(self, index):
+        # Index may also be a slice.
+        return tuple(getattr(self, f.name) for f in self._struct)[index]
+
+    def __setitem__(self, index, value):
+        if isinstance(index, slice):
+            fnames = [f.name for f in self._struct][index]
+            values = list(value)
+            if len(values) < len(fnames):
+                word = 'value' if len(values) == 1 else 'values'
+                raise ValueError('need more than {} {} to '
+                                 'unpack'.format(len(fnames), word))
+            elif len(values) > len(fnames):
+                raise ValueError('too many values to unpack (expected '
+                                 '{})'.format(len(fnames)))
+            for fname, v in zip(fnames, values):
+                setattr(self, fname, v)
+        else:
+            setattr(self, self._struct[index].name, value)
+
     def __reduce_ex__(self, protocol):
         # We use __reduce_ex__() rather than __getnewargs__() so that
         # the metaclass's __call__() will still run. This is needed to

tests/test_fields.py

@@ -40,5 +40,19 @@ class Foo(Struct):
             bar = TypedField(int, or_none=True)
         f1 = Foo(None)
 
+    def test_nestedstructs(self):
+        class Bar(Struct):
+            a = Field
+        class Foo(Struct):
+            b = Field
+            c = TypedField(Bar)
+        f = Foo(1, (2,))
+        self.assertEqual(f.c.a, 2)
+        self.assertEqual(f.b, 1)
+        with self.assertRaises(TypeError):
+            f = Foo(1, 2)
+        with self.assertRaises(TypeError):
+            f = Foo(1, (2, 3))
+
 if __name__ == '__main__':
     unittest.main()

tests/test_struct.py

@@ -84,6 +84,38 @@ class Foo(Struct):
         self.assertEqual(len(f), 2)
         self.assertEqual((a, b), (1, 2))
 
+    def test_indexing(self):
+        class Bar(Struct):
+            a = Field
+            b = Field
+        f = Bar(5, 6)
+        self.assertEqual(f[0], 5)
+        self.assertEqual(f[1], 6)
+        self.assertEqual(f[0:2], (5, 6))
+        self.assertEqual(f[0:0], ())
+        self.assertEqual(f[0:2:2], (5,))
+        self.assertEqual(f[1:-1], ())
+        self.assertEqual(f[-1:10], (6,))
+        with self.assertRaises(IndexError):
+            f[2]
+        with self.assertRaises(AttributeError):
+            f[0] = 4
+
+        class Bar(Struct):
+            _immutable = False
+            a = Field()
+            b = Field()
+        f = Bar(5, 6)
+        f[0] = 4
+        self.assertEqual(f.a, 4)
+        f[::-1] = (1, 2)
+        self.assertEqual(f.a, 2)
+        self.assertEqual(f.b, 1)
+        with self.assertRaises(ValueError):
+            f[:] = (1,)
+        with self.assertRaises(ValueError):
+            f[:] = (1, 2, 3)
+
     def test_construct(self):
         # Construction by keyword.
         class Foo(Struct):
@@ -101,10 +133,13 @@ class Foo(Struct):
         class Foo(Struct):
             a = Field()
             b = Field(default='b')
+            # Make sure default field values are passed to __init__() too.
+            def __init__(self, a, b):
+                self.c = b
         f = Foo(1, 2)
-        self.assertEqual((f.a, f.b), (1, 2))
+        self.assertEqual((f.a, f.b, f.c), (1, 2, 2))
         f = Foo(1)
-        self.assertEqual((f.a, f.b), (1, 'b'))
+        self.assertEqual((f.a, f.b, f.c), (1, 'b', 'b'))
 
         # Parentheses-less shorthand.
         class Foo(Struct):