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| 1 #!/usr/bin/env python | |
| 2 # | |
| 3 # Copyright 2014 Google Inc. All rights reserved. | |
| 4 # | |
| 5 # Licensed under the Apache License, Version 2.0 (the "License"); | |
| 6 # you may not use this file except in compliance with the License. | |
| 7 # You may obtain a copy of the License at | |
| 8 # | |
| 9 # http://www.apache.org/licenses/LICENSE-2.0 | |
| 10 # | |
| 11 # Unless required by applicable law or agreed to in writing, software | |
| 12 # distributed under the License is distributed on an "AS IS" BASIS, | |
| 13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
| 14 # See the License for the specific language governing permissions and | |
| 15 # limitations under the License. | |
| 16 # | |
| 17 | |
| 18 """Common utility library.""" | |
| 19 | |
| 20 __author__ = [ | |
| 21 'rafek@google.com (Rafe Kaplan)', | |
| 22 'guido@google.com (Guido van Rossum)', | |
| 23 ] | |
| 24 | |
| 25 __all__ = [ | |
| 26 'positional', | |
| 27 'POSITIONAL_WARNING', | |
| 28 'POSITIONAL_EXCEPTION', | |
| 29 'POSITIONAL_IGNORE', | |
| 30 ] | |
| 31 | |
| 32 import inspect | |
| 33 import logging | |
| 34 import sys | |
| 35 import types | |
| 36 | |
| 37 import six | |
| 38 from six.moves import urllib | |
| 39 | |
| 40 | |
| 41 logger = logging.getLogger(__name__) | |
| 42 | |
| 43 POSITIONAL_WARNING = 'WARNING' | |
| 44 POSITIONAL_EXCEPTION = 'EXCEPTION' | |
| 45 POSITIONAL_IGNORE = 'IGNORE' | |
| 46 POSITIONAL_SET = frozenset([POSITIONAL_WARNING, POSITIONAL_EXCEPTION, | |
| 47 POSITIONAL_IGNORE]) | |
| 48 | |
| 49 positional_parameters_enforcement = POSITIONAL_WARNING | |
| 50 | |
| 51 def positional(max_positional_args): | |
| 52 """A decorator to declare that only the first N arguments my be positional. | |
| 53 | |
| 54 This decorator makes it easy to support Python 3 style key-word only | |
| 55 parameters. For example, in Python 3 it is possible to write: | |
| 56 | |
| 57 def fn(pos1, *, kwonly1=None, kwonly1=None): | |
| 58 ... | |
| 59 | |
| 60 All named parameters after * must be a keyword: | |
| 61 | |
| 62 fn(10, 'kw1', 'kw2') # Raises exception. | |
| 63 fn(10, kwonly1='kw1') # Ok. | |
| 64 | |
| 65 Example: | |
| 66 To define a function like above, do: | |
| 67 | |
| 68 @positional(1) | |
| 69 def fn(pos1, kwonly1=None, kwonly2=None): | |
| 70 ... | |
| 71 | |
| 72 If no default value is provided to a keyword argument, it becomes a required | |
| 73 keyword argument: | |
| 74 | |
| 75 @positional(0) | |
| 76 def fn(required_kw): | |
| 77 ... | |
| 78 | |
| 79 This must be called with the keyword parameter: | |
| 80 | |
| 81 fn() # Raises exception. | |
| 82 fn(10) # Raises exception. | |
| 83 fn(required_kw=10) # Ok. | |
| 84 | |
| 85 When defining instance or class methods always remember to account for | |
| 86 'self' and 'cls': | |
| 87 | |
| 88 class MyClass(object): | |
| 89 | |
| 90 @positional(2) | |
| 91 def my_method(self, pos1, kwonly1=None): | |
| 92 ... | |
| 93 | |
| 94 @classmethod | |
| 95 @positional(2) | |
| 96 def my_method(cls, pos1, kwonly1=None): | |
| 97 ... | |
| 98 | |
| 99 The positional decorator behavior is controlled by | |
| 100 util.positional_parameters_enforcement, which may be set to | |
| 101 POSITIONAL_EXCEPTION, POSITIONAL_WARNING or POSITIONAL_IGNORE to raise an | |
| 102 exception, log a warning, or do nothing, respectively, if a declaration is | |
| 103 violated. | |
| 104 | |
| 105 Args: | |
| 106 max_positional_arguments: Maximum number of positional arguments. All | |
| 107 parameters after the this index must be keyword only. | |
| 108 | |
| 109 Returns: | |
| 110 A decorator that prevents using arguments after max_positional_args from | |
| 111 being used as positional parameters. | |
| 112 | |
| 113 Raises: | |
| 114 TypeError if a key-word only argument is provided as a positional | |
| 115 parameter, but only if util.positional_parameters_enforcement is set to | |
| 116 POSITIONAL_EXCEPTION. | |
| 117 """ | |
| 118 def positional_decorator(wrapped): | |
| 119 def positional_wrapper(*args, **kwargs): | |
| 120 if len(args) > max_positional_args: | |
| 121 plural_s = '' | |
| 122 if max_positional_args != 1: | |
| 123 plural_s = 's' | |
| 124 message = '%s() takes at most %d positional argument%s (%d given)' % ( | |
| 125 wrapped.__name__, max_positional_args, plural_s, len(args)) | |
| 126 if positional_parameters_enforcement == POSITIONAL_EXCEPTION: | |
| 127 raise TypeError(message) | |
| 128 elif positional_parameters_enforcement == POSITIONAL_WARNING: | |
| 129 logger.warning(message) | |
| 130 else: # IGNORE | |
| 131 pass | |
| 132 return wrapped(*args, **kwargs) | |
| 133 return positional_wrapper | |
| 134 | |
| 135 if isinstance(max_positional_args, six.integer_types): | |
| 136 return positional_decorator | |
| 137 else: | |
| 138 args, _, _, defaults = inspect.getargspec(max_positional_args) | |
| 139 return positional(len(args) - len(defaults))(max_positional_args) | |
| 140 | |
| 141 | |
| 142 def scopes_to_string(scopes): | |
| 143 """Converts scope value to a string. | |
| 144 | |
| 145 If scopes is a string then it is simply passed through. If scopes is an | |
| 146 iterable then a string is returned that is all the individual scopes | |
| 147 concatenated with spaces. | |
| 148 | |
| 149 Args: | |
| 150 scopes: string or iterable of strings, the scopes. | |
| 151 | |
| 152 Returns: | |
| 153 The scopes formatted as a single string. | |
| 154 """ | |
| 155 if isinstance(scopes, six.string_types): | |
| 156 return scopes | |
| 157 else: | |
| 158 return ' '.join(scopes) | |
| 159 | |
| 160 | |
| 161 def dict_to_tuple_key(dictionary): | |
| 162 """Converts a dictionary to a tuple that can be used as an immutable key. | |
| 163 | |
| 164 The resulting key is always sorted so that logically equivalent dictionaries | |
| 165 always produce an identical tuple for a key. | |
| 166 | |
| 167 Args: | |
| 168 dictionary: the dictionary to use as the key. | |
| 169 | |
| 170 Returns: | |
| 171 A tuple representing the dictionary in it's naturally sorted ordering. | |
| 172 """ | |
| 173 return tuple(sorted(dictionary.items())) | |
| 174 | |
| 175 | |
| 176 def _add_query_parameter(url, name, value): | |
| 177 """Adds a query parameter to a url. | |
| 178 | |
| 179 Replaces the current value if it already exists in the URL. | |
| 180 | |
| 181 Args: | |
| 182 url: string, url to add the query parameter to. | |
| 183 name: string, query parameter name. | |
| 184 value: string, query parameter value. | |
| 185 | |
| 186 Returns: | |
| 187 Updated query parameter. Does not update the url if value is None. | |
| 188 """ | |
| 189 if value is None: | |
| 190 return url | |
| 191 else: | |
| 192 parsed = list(urllib.parse.urlparse(url)) | |
| 193 q = dict(urllib.parse.parse_qsl(parsed[4])) | |
| 194 q[name] = value | |
| 195 parsed[4] = urllib.parse.urlencode(q) | |
| 196 return urllib.parse.urlunparse(parsed) | |
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