Add test_decorators

Author: palaviv

Lib/test/test_decorators.py

@@ -0,0 +1,304 @@
+import unittest
+
+def funcattrs(**kwds):
+    def decorate(func):
+        func.__dict__.update(kwds)
+        return func
+    return decorate
+
+class MiscDecorators (object):
+    @staticmethod
+    def author(name):
+        def decorate(func):
+            func.__dict__['author'] = name
+            return func
+        return decorate
+
+# -----------------------------------------------
+
+class DbcheckError (Exception):
+    def __init__(self, exprstr, func, args, kwds):
+        # A real version of this would set attributes here
+        Exception.__init__(self, "dbcheck %r failed (func=%s args=%s kwds=%s)" %
+                           (exprstr, func, args, kwds))
+
+
+def dbcheck(exprstr, globals=None, locals=None):
+    "Decorator to implement debugging assertions"
+    def decorate(func):
+        expr = compile(exprstr, "dbcheck-%s" % func.__name__, "eval")
+        def check(*args, **kwds):
+            if not eval(expr, globals, locals):
+                raise DbcheckError(exprstr, func, args, kwds)
+            return func(*args, **kwds)
+        return check
+    return decorate
+
+# -----------------------------------------------
+
+def countcalls(counts):
+    "Decorator to count calls to a function"
+    def decorate(func):
+        func_name = func.__name__
+        counts[func_name] = 0
+        def call(*args, **kwds):
+            counts[func_name] += 1
+            return func(*args, **kwds)
+        call.__name__ = func_name
+        return call
+    return decorate
+
+# -----------------------------------------------
+
+def memoize(func):
+    saved = {}
+    def call(*args):
+        try:
+            return saved[args]
+        except KeyError:
+            res = func(*args)
+            saved[args] = res
+            return res
+        except TypeError:
+            # Unhashable argument
+            return func(*args)
+    call.__name__ = func.__name__
+    return call
+
+# -----------------------------------------------
+
+class TestDecorators(unittest.TestCase):
+
+    def test_single(self):
+        class C(object):
+            @staticmethod
+            def foo(): return 42
+        self.assertEqual(C.foo(), 42)
+        self.assertEqual(C().foo(), 42)
+
+    def test_staticmethod_function(self):
+        @staticmethod
+        def notamethod(x):
+            return x
+        self.assertRaises(TypeError, notamethod, 1)
+
+    def test_dotted(self):
+        decorators = MiscDecorators()
+        @decorators.author('Cleese')
+        def foo(): return 42
+        self.assertEqual(foo(), 42)
+        self.assertEqual(foo.author, 'Cleese')
+
+    def test_argforms(self):
+        # A few tests of argument passing, as we use restricted form
+        # of expressions for decorators.
+
+        def noteargs(*args, **kwds):
+            def decorate(func):
+                setattr(func, 'dbval', (args, kwds))
+                return func
+            return decorate
+
+        args = ( 'Now', 'is', 'the', 'time' )
+        kwds = dict(one=1, two=2)
+        @noteargs(*args, **kwds)
+        def f1(): return 42
+        self.assertEqual(f1(), 42)
+        self.assertEqual(f1.dbval, (args, kwds))
+
+        @noteargs('terry', 'gilliam', eric='idle', john='cleese')
+        def f2(): return 84
+        self.assertEqual(f2(), 84)
+        self.assertEqual(f2.dbval, (('terry', 'gilliam'),
+                                     dict(eric='idle', john='cleese')))
+
+        @noteargs(1, 2,)
+        def f3(): pass
+        self.assertEqual(f3.dbval, ((1, 2), {}))
+
+    def test_dbcheck(self):
+        @dbcheck('args[1] is not None')
+        def f(a, b):
+            return a + b
+        self.assertEqual(f(1, 2), 3)
+        self.assertRaises(DbcheckError, f, 1, None)
+
+    def test_memoize(self):
+        counts = {}
+
+        @memoize
+        @countcalls(counts)
+        def double(x):
+            return x * 2
+        self.assertEqual(double.__name__, 'double')
+
+        self.assertEqual(counts, dict(double=0))
+
+        # Only the first call with a given argument bumps the call count:
+        #
+        self.assertEqual(double(2), 4)
+        self.assertEqual(counts['double'], 1)
+        self.assertEqual(double(2), 4)
+        self.assertEqual(counts['double'], 1)
+        self.assertEqual(double(3), 6)
+        self.assertEqual(counts['double'], 2)
+
+        # Unhashable arguments do not get memoized:
+        #
+        self.assertEqual(double([10]), [10, 10])
+        self.assertEqual(counts['double'], 3)
+        self.assertEqual(double([10]), [10, 10])
+        self.assertEqual(counts['double'], 4)
+
+    def test_errors(self):
+        # Test syntax restrictions - these are all compile-time errors:
+        #
+        for expr in [ "1+2", "x[3]", "(1, 2)" ]:
+            # Sanity check: is expr is a valid expression by itself?
+            compile(expr, "testexpr", "exec")
+
+            codestr = "@%s\ndef f(): pass" % expr
+            self.assertRaises(SyntaxError, compile, codestr, "test", "exec")
+
+        # You can't put multiple decorators on a single line:
+        #
+        self.assertRaises(SyntaxError, compile,
+                          "@f1 @f2\ndef f(): pass", "test", "exec")
+
+        # Test runtime errors
+
+        def unimp(func):
+            raise NotImplementedError
+        context = dict(nullval=None, unimp=unimp)
+
+        for expr, exc in [ ("undef", NameError),
+                           ("nullval", TypeError),
+                           ("nullval.attr", AttributeError),
+                           ("unimp", NotImplementedError)]:
+            codestr = "@%s\ndef f(): pass\nassert f() is None" % expr
+            code = compile(codestr, "test", "exec")
+            self.assertRaises(exc, eval, code, context)
+
+    def test_double(self):
+        class C(object):
+            @funcattrs(abc=1, xyz="haha")
+            @funcattrs(booh=42)
+            def foo(self): return 42
+        self.assertEqual(C().foo(), 42)
+        self.assertEqual(C.foo.abc, 1)
+        self.assertEqual(C.foo.xyz, "haha")
+        self.assertEqual(C.foo.booh, 42)
+
+    def test_order(self):
+        # Test that decorators are applied in the proper order to the function
+        # they are decorating.
+        def callnum(num):
+            """Decorator factory that returns a decorator that replaces the
+            passed-in function with one that returns the value of 'num'"""
+            def deco(func):
+                return lambda: num
+            return deco
+        @callnum(2)
+        @callnum(1)
+        def foo(): return 42
+        self.assertEqual(foo(), 2,
+                            "Application order of decorators is incorrect")
+
+    def test_eval_order(self):
+        # Evaluating a decorated function involves four steps for each
+        # decorator-maker (the function that returns a decorator):
+        #
+        #    1: Evaluate the decorator-maker name
+        #    2: Evaluate the decorator-maker arguments (if any)
+        #    3: Call the decorator-maker to make a decorator
+        #    4: Call the decorator
+        #
+        # When there are multiple decorators, these steps should be
+        # performed in the above order for each decorator, but we should
+        # iterate through the decorators in the reverse of the order they
+        # appear in the source.
+
+        actions = []
+
+        def make_decorator(tag):
+            actions.append('makedec' + tag)
+            def decorate(func):
+                actions.append('calldec' + tag)
+                return func
+            return decorate
+
+        class NameLookupTracer (object):
+            def __init__(self, index):
+                self.index = index
+
+            def __getattr__(self, fname):
+                if fname == 'make_decorator':
+                    opname, res = ('evalname', make_decorator)
+                elif fname == 'arg':
+                    opname, res = ('evalargs', str(self.index))
+                else:
+                    assert False, "Unknown attrname %s" % fname
+                actions.append('%s%d' % (opname, self.index))
+                return res
+
+        c1, c2, c3 = map(NameLookupTracer, [ 1, 2, 3 ])
+
+        expected_actions = [ 'evalname1', 'evalargs1', 'makedec1',
+                             'evalname2', 'evalargs2', 'makedec2',
+                             'evalname3', 'evalargs3', 'makedec3',
+                             'calldec3', 'calldec2', 'calldec1' ]
+
+        actions = []
+        @c1.make_decorator(c1.arg)
+        @c2.make_decorator(c2.arg)
+        @c3.make_decorator(c3.arg)
+        def foo(): return 42
+        self.assertEqual(foo(), 42)
+
+        self.assertEqual(actions, expected_actions)
+
+        # Test the equivalence claim in chapter 7 of the reference manual.
+        #
+        actions = []
+        def bar(): return 42
+        bar = c1.make_decorator(c1.arg)(c2.make_decorator(c2.arg)(c3.make_decorator(c3.arg)(bar)))
+        self.assertEqual(bar(), 42)
+        self.assertEqual(actions, expected_actions)
+
+class TestClassDecorators(unittest.TestCase):
+
+    def test_simple(self):
+        def plain(x):
+            x.extra = 'Hello'
+            return x
+        @plain
+        class C(object): pass
+        self.assertEqual(C.extra, 'Hello')
+
+    def test_double(self):
+        def ten(x):
+            x.extra = 10
+            return x
+        def add_five(x):
+            x.extra += 5
+            return x
+
+        @add_five
+        @ten
+        class C(object): pass
+        self.assertEqual(C.extra, 15)
+
+    def test_order(self):
+        def applied_first(x):
+            x.extra = 'first'
+            return x
+        def applied_second(x):
+            x.extra = 'second'
+            return x
+        @applied_second
+        @applied_first
+        class C(object): pass
+        self.assertEqual(C.extra, 'second')
+
+if __name__ == "__main__":
+    unittest.main()