Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 1 | #!/usr/bin/env python |
| 2 | # |
| 3 | # Copyright 2010 Google Inc. |
| 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__ = ['rafek@google.com (Rafe Kaplan)', |
| 21 | 'guido@google.com (Guido van Rossum)', |
| 22 | ] |
| 23 | __all__ = [ |
| 24 | 'positional', |
Joe Gregorio | 79daca0 | 2013-03-29 16:25:52 -0400 | [diff] [blame] | 25 | 'POSITIONAL_WARNING', |
| 26 | 'POSITIONAL_EXCEPTION', |
| 27 | 'POSITIONAL_IGNORE', |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 28 | ] |
| 29 | |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 30 | import inspect |
| 31 | import logging |
Joe Gregorio | 5cf5d12 | 2012-11-16 16:36:12 -0500 | [diff] [blame] | 32 | import types |
Joe Gregorio | 1024403 | 2013-03-06 09:48:04 -0500 | [diff] [blame] | 33 | import urllib |
| 34 | import urlparse |
| 35 | |
| 36 | try: |
| 37 | from urlparse import parse_qsl |
| 38 | except ImportError: |
| 39 | from cgi import parse_qsl |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 40 | |
| 41 | logger = logging.getLogger(__name__) |
| 42 | |
Joe Gregorio | 79daca0 | 2013-03-29 16:25:52 -0400 | [diff] [blame] | 43 | POSITIONAL_WARNING = 'WARNING' |
| 44 | POSITIONAL_EXCEPTION = 'EXCEPTION' |
| 45 | POSITIONAL_IGNORE = 'IGNORE' |
| 46 | POSITIONAL_SET = frozenset([POSITIONAL_WARNING, POSITIONAL_EXCEPTION, |
| 47 | POSITIONAL_IGNORE]) |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 48 | |
Joe Gregorio | 79daca0 | 2013-03-29 16:25:52 -0400 | [diff] [blame] | 49 | positional_parameters_enforcement = POSITIONAL_WARNING |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 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 |
Joe Gregorio | e2233cd | 2013-01-24 15:46:23 -0500 | [diff] [blame] | 55 | parameters. For example, in Python 3 it is possible to write: |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 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 | |
Joe Gregorio | 79daca0 | 2013-03-29 16:25:52 -0400 | [diff] [blame] | 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. |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 104 | |
| 105 | Args: |
Joe Gregorio | e2233cd | 2013-01-24 15:46:23 -0500 | [diff] [blame] | 106 | max_positional_arguments: Maximum number of positional arguments. All |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 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: |
Joe Gregorio | 79daca0 | 2013-03-29 16:25:52 -0400 | [diff] [blame] | 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. |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 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)) |
Joe Gregorio | 79daca0 | 2013-03-29 16:25:52 -0400 | [diff] [blame] | 126 | if positional_parameters_enforcement == POSITIONAL_EXCEPTION: |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 127 | raise TypeError(message) |
Joe Gregorio | 79daca0 | 2013-03-29 16:25:52 -0400 | [diff] [blame] | 128 | elif positional_parameters_enforcement == POSITIONAL_WARNING: |
Joe Gregorio | 68a8cfe | 2012-08-03 16:17:40 -0400 | [diff] [blame] | 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, (int, long)): |
| 136 | return positional_decorator |
| 137 | else: |
| 138 | args, _, _, defaults = inspect.getargspec(max_positional_args) |
| 139 | return positional(len(args) - len(defaults))(max_positional_args) |
Joe Gregorio | 5cf5d12 | 2012-11-16 16:36:12 -0500 | [diff] [blame] | 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, types.StringTypes): |
| 156 | return scopes |
| 157 | else: |
| 158 | return ' '.join(scopes) |
Joe Gregorio | e2233cd | 2013-01-24 15:46:23 -0500 | [diff] [blame] | 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())) |
Joe Gregorio | 1024403 | 2013-03-06 09:48:04 -0500 | [diff] [blame] | 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(urlparse.urlparse(url)) |
| 193 | q = dict(parse_qsl(parsed[4])) |
| 194 | q[name] = value |
| 195 | parsed[4] = urllib.urlencode(q) |
| 196 | return urlparse.urlunparse(parsed) |