Lib/test/test_decorators.py

   1 import unittest
   2 from test import test_support
   3
   4 def funcattrs(**kwds):
   5     def decorate(func):
   6         func.__dict__.update(kwds)
   7         return func
   8     return decorate
   9
  10 class MiscDecorators (object):
  11     @staticmethod
  12     def author(name):
  13         def decorate(func):
  14             func.__dict__['author'] = name
  15             return func
  16         return decorate
  17
  18 # -----------------------------------------------
  19
  20 class DbcheckError (Exception):
  21     def __init__(self, exprstr, func, args, kwds):
  22         # A real version of this would set attributes here
  23         Exception.__init__(self, "dbcheck %r failed (func=%s args=%s kwds=%s)" %
  24                            (exprstr, func, args, kwds))
  25
  26
  27 def dbcheck(exprstr, globals=None, locals=None):
  28     "Decorator to implement debugging assertions"
  29     def decorate(func):
  30         expr = compile(exprstr, "dbcheck-%s" % func.func_name, "eval")
  31         def check(*args, **kwds):
  32             if not eval(expr, globals, locals):
  33                 raise DbcheckError(exprstr, func, args, kwds)
  34             return func(*args, **kwds)
  35         return check
  36     return decorate
  37
  38 # -----------------------------------------------
  39
  40 def countcalls(counts):
  41     "Decorator to count calls to a function"
  42     def decorate(func):
  43         func_name = func.func_name
  44         counts[func_name] = 0
  45         def call(*args, **kwds):
  46             counts[func_name] += 1
  47             return func(*args, **kwds)
  48         call.func_name = func_name
  49         return call
  50     return decorate
  51
  52 # -----------------------------------------------
  53
  54 def memoize(func):
  55     saved = {}
  56     def call(*args):
  57         try:
  58             return saved[args]
  59         except KeyError:
  60             res = func(*args)
  61             saved[args] = res
  62             return res
  63         except TypeError:
  64             # Unhashable argument
  65             return func(*args)
  66     call.func_name = func.func_name
  67     return call
  68
  69 # -----------------------------------------------
  70
  71 class TestDecorators(unittest.TestCase):
  72
  73     def test_single(self):
  74         class C(object):
  75             @staticmethod
  76             def foo(): return 42
  77         self.assertEqual(C.foo(), 42)
  78         self.assertEqual(C().foo(), 42)
  79
  80     def test_staticmethod_function(self):
  81         @staticmethod
  82         def notamethod(x):
  83             return x
  84         self.assertRaises(TypeError, notamethod, 1)
  85
  86     def test_dotted(self):
  87         decorators = MiscDecorators()
  88         @decorators.author('Cleese')
  89         def foo(): return 42
  90         self.assertEqual(foo(), 42)
  91         self.assertEqual(foo.author, 'Cleese')
  92
  93     def test_argforms(self):
  94         # A few tests of argument passing, as we use restricted form
  95         # of expressions for decorators.
  96
  97         def noteargs(*args, **kwds):
  98             def decorate(func):
  99                 setattr(func, 'dbval', (args, kwds))
 100                 return func
 101             return decorate
 102
 103         args = ( 'Now', 'is', 'the', 'time' )
 104         kwds = dict(one=1, two=2)
 105         @noteargs(*args, **kwds)
 106         def f1(): return 42
 107         self.assertEqual(f1(), 42)
 108         self.assertEqual(f1.dbval, (args, kwds))
 109
 110         @noteargs('terry', 'gilliam', eric='idle', john='cleese')
 111         def f2(): return 84
 112         self.assertEqual(f2(), 84)
 113         self.assertEqual(f2.dbval, (('terry', 'gilliam'),
 114                                      dict(eric='idle', john='cleese')))
 115
 116         @noteargs(1, 2,)
 117         def f3(): pass
 118         self.assertEqual(f3.dbval, ((1, 2), {}))
 119
 120     def test_dbcheck(self):
 121         @dbcheck('args[1] is not None')
 122         def f(a, b):
 123             return a + b
 124         self.assertEqual(f(1, 2), 3)
 125         self.assertRaises(DbcheckError, f, 1, None)
 126
 127     def test_memoize(self):
 128         counts = {}
 129
 130         @memoize
 131         @countcalls(counts)
 132         def double(x):
 133             return x * 2
 134         self.assertEqual(double.func_name, 'double')
 135
 136         self.assertEqual(counts, dict(double=0))
 137
 138         # Only the first call with a given argument bumps the call count:
 139         #
 140         self.assertEqual(double(2), 4)
 141         self.assertEqual(counts['double'], 1)
 142         self.assertEqual(double(2), 4)
 143         self.assertEqual(counts['double'], 1)
 144         self.assertEqual(double(3), 6)
 145         self.assertEqual(counts['double'], 2)
 146
 147         # Unhashable arguments do not get memoized:
 148         #
 149         self.assertEqual(double([10]), [10, 10])
 150         self.assertEqual(counts['double'], 3)
 151         self.assertEqual(double([10]), [10, 10])
 152         self.assertEqual(counts['double'], 4)
 153
 154     def test_errors(self):
 155         # Test syntax restrictions - these are all compile-time errors:
 156         #
 157         for expr in [ "1+2", "x[3]", "(1, 2)" ]:
 158             # Sanity check: is expr is a valid expression by itself?
 159             compile(expr, "testexpr", "exec")
 160
 161             codestr = "@%s\ndef f(): pass" % expr
 162             self.assertRaises(SyntaxError, compile, codestr, "test", "exec")
 163
 164         # You can't put multiple decorators on a single line:
 165         #
 166         self.assertRaises(SyntaxError, compile,
 167                           "@f1 @f2\ndef f(): pass", "test", "exec")
 168
 169         # Test runtime errors
 170
 171         def unimp(func):
 172             raise NotImplementedError
 173         context = dict(nullval=None, unimp=unimp)
 174
 175         for expr, exc in [ ("undef", NameError),
 176                            ("nullval", TypeError),
 177                            ("nullval.attr", AttributeError),
 178                            ("unimp", NotImplementedError)]:
 179             codestr = "@%s\ndef f(): pass\nassert f() is None" % expr
 180             code = compile(codestr, "test", "exec")
 181             self.assertRaises(exc, eval, code, context)
 182
 183     def test_double(self):
 184         class C(object):
 185             @funcattrs(abc=1, xyz="haha")
 186             @funcattrs(booh=42)
 187             def foo(self): return 42
 188         self.assertEqual(C().foo(), 42)
 189         self.assertEqual(C.foo.abc, 1)
 190         self.assertEqual(C.foo.xyz, "haha")
 191         self.assertEqual(C.foo.booh, 42)
 192
 193     def test_order(self):
 194         # Test that decorators are applied in the proper order to the function
 195         # they are decorating.
 196         def callnum(num):
 197             """Decorator factory that returns a decorator that replaces the
 198             passed-in function with one that returns the value of 'num'"""
 199             def deco(func):
 200                 return lambda: num
 201             return deco
 202         @callnum(2)
 203         @callnum(1)
 204         def foo(): return 42
 205         self.assertEqual(foo(), 2,
 206                             "Application order of decorators is incorrect")
 207
 208     def test_eval_order(self):
 209         # Evaluating a decorated function involves four steps for each
 210         # decorator-maker (the function that returns a decorator):
 211         #
 212         #    1: Evaluate the decorator-maker name
 213         #    2: Evaluate the decorator-maker arguments (if any)
 214         #    3: Call the decorator-maker to make a decorator
 215         #    4: Call the decorator
 216         #
 217         # When there are multiple decorators, these steps should be
 218         # performed in the above order for each decorator, but we should
 219         # iterate through the decorators in the reverse of the order they
 220         # appear in the source.
 221
 222         actions = []
 223
 224         def make_decorator(tag):
 225             actions.append('makedec' + tag)
 226             def decorate(func):
 227                 actions.append('calldec' + tag)
 228                 return func
 229             return decorate
 230
 231         class NameLookupTracer (object):
 232             def __init__(self, index):
 233                 self.index = index
 234
 235             def __getattr__(self, fname):
 236                 if fname == 'make_decorator':
 237                     opname, res = ('evalname', make_decorator)
 238                 elif fname == 'arg':
 239                     opname, res = ('evalargs', str(self.index))
 240                 else:
 241                     assert False, "Unknown attrname %s" % fname
 242                 actions.append('%s%d' % (opname, self.index))
 243                 return res
 244
 245         c1, c2, c3 = map(NameLookupTracer, [ 1, 2, 3 ])
 246
 247         expected_actions = [ 'evalname1', 'evalargs1', 'makedec1',
 248                              'evalname2', 'evalargs2', 'makedec2',
 249                              'evalname3', 'evalargs3', 'makedec3',
 250                              'calldec3', 'calldec2', 'calldec1' ]
 251
 252         actions = []
 253         @c1.make_decorator(c1.arg)
 254         @c2.make_decorator(c2.arg)
 255         @c3.make_decorator(c3.arg)
 256         def foo(): return 42
 257         self.assertEqual(foo(), 42)
 258
 259         self.assertEqual(actions, expected_actions)
 260
 261         # Test the equivalence claim in chapter 7 of the reference manual.
 262         #
 263         actions = []
 264         def bar(): return 42
 265         bar = c1.make_decorator(c1.arg)(c2.make_decorator(c2.arg)(c3.make_decorator(c3.arg)(bar)))
 266         self.assertEqual(bar(), 42)
 267         self.assertEqual(actions, expected_actions)
 268
 269 class TestClassDecorators(unittest.TestCase):
 270
 271     def test_simple(self):
 272         def plain(x):
 273             x.extra = 'Hello'
 274             return x
 275         @plain
 276         class C(object): pass
 277         self.assertEqual(C.extra, 'Hello')
 278
 279     def test_double(self):
 280         def ten(x):
 281             x.extra = 10
 282             return x
 283         def add_five(x):
 284             x.extra += 5
 285             return x
 286
 287         @add_five
 288         @ten
 289         class C(object): pass
 290         self.assertEqual(C.extra, 15)
 291
 292     def test_order(self):
 293         def applied_first(x):
 294             x.extra = 'first'
 295             return x
 296         def applied_second(x):
 297             x.extra = 'second'
 298             return x
 299         @applied_second
 300         @applied_first
 301         class C(object): pass
 302         self.assertEqual(C.extra, 'second')
 303
 304 def test_main():
 305     test_support.run_unittest(TestDecorators)
 306     test_support.run_unittest(TestClassDecorators)
 307
 308 if __name__=="__main__":
 309     test_main()