Lib/warnings.py

   1 """Python part of the warnings subsystem."""
   2
   3 # Note: function level imports should *not* be used
   4 # in this module as it may cause import lock deadlock.
   5 # See bug 683658.
   6 import linecache
   7 import sys
   8 import types
   9
  10 __all__ = ["warn", "showwarning", "formatwarning", "filterwarnings",
  11            "resetwarnings", "catch_warnings"]
  12
  13
  14 def warnpy3k(message, category=None, stacklevel=1):
  15     """Issue a deprecation warning for Python 3.x related changes.
  16
  17     Warnings are omitted unless Python is started with the -3 option.
  18     """
  19     if sys.py3kwarning:
  20         if category is None:
  21             category = DeprecationWarning
  22         warn(message, category, stacklevel+1)
  23
  24 def _show_warning(message, category, filename, lineno, file=None, line=None):
  25     """Hook to write a warning to a file; replace if you like."""
  26     if file is None:
  27         file = sys.stderr
  28     try:
  29         file.write(formatwarning(message, category, filename, lineno, line))
  30     except IOError:
  31         pass # the file (probably stderr) is invalid - this warning gets lost.
  32 # Keep a worrking version around in case the deprecation of the old API is
  33 # triggered.
  34 showwarning = _show_warning
  35
  36 def formatwarning(message, category, filename, lineno, line=None):
  37     """Function to format a warning the standard way."""
  38     s =  "%s:%s: %s: %s\n" % (filename, lineno, category.__name__, message)
  39     line = linecache.getline(filename, lineno) if line is None else line
  40     if line:
  41         line = line.strip()
  42         s += "  %s\n" % line
  43     return s
  44
  45 def filterwarnings(action, message="", category=Warning, module="", lineno=0,
  46                    append=0):
  47     """Insert an entry into the list of warnings filters (at the front).
  48
  49     Use assertions to check that all arguments have the right type."""
  50     import re
  51     assert action in ("error", "ignore", "always", "default", "module",
  52                       "once"), "invalid action: %r" % (action,)
  53     assert isinstance(message, basestring), "message must be a string"
  54     assert isinstance(category, (type, types.ClassType)), \
  55            "category must be a class"
  56     assert issubclass(category, Warning), "category must be a Warning subclass"
  57     assert isinstance(module, basestring), "module must be a string"
  58     assert isinstance(lineno, int) and lineno >= 0, \
  59            "lineno must be an int >= 0"
  60     item = (action, re.compile(message, re.I), category,
  61             re.compile(module), lineno)
  62     if append:
  63         filters.append(item)
  64     else:
  65         filters.insert(0, item)
  66
  67 def simplefilter(action, category=Warning, lineno=0, append=0):
  68     """Insert a simple entry into the list of warnings filters (at the front).
  69
  70     A simple filter matches all modules and messages.
  71     """
  72     assert action in ("error", "ignore", "always", "default", "module",
  73                       "once"), "invalid action: %r" % (action,)
  74     assert isinstance(lineno, int) and lineno >= 0, \
  75            "lineno must be an int >= 0"
  76     item = (action, None, category, None, lineno)
  77     if append:
  78         filters.append(item)
  79     else:
  80         filters.insert(0, item)
  81
  82 def resetwarnings():
  83     """Clear the list of warning filters, so that no filters are active."""
  84     filters[:] = []
  85
  86 class _OptionError(Exception):
  87     """Exception used by option processing helpers."""
  88     pass
  89
  90 # Helper to process -W options passed via sys.warnoptions
  91 def _processoptions(args):
  92     for arg in args:
  93         try:
  94             _setoption(arg)
  95         except _OptionError, msg:
  96             print >>sys.stderr, "Invalid -W option ignored:", msg
  97
  98 # Helper for _processoptions()
  99 def _setoption(arg):
 100     import re
 101     parts = arg.split(':')
 102     if len(parts) > 5:
 103         raise _OptionError("too many fields (max 5): %r" % (arg,))
 104     while len(parts) < 5:
 105         parts.append('')
 106     action, message, category, module, lineno = [s.strip()
 107                                                  for s in parts]
 108     action = _getaction(action)
 109     message = re.escape(message)
 110     category = _getcategory(category)
 111     module = re.escape(module)
 112     if module:
 113         module = module + '$'
 114     if lineno:
 115         try:
 116             lineno = int(lineno)
 117             if lineno < 0:
 118                 raise ValueError
 119         except (ValueError, OverflowError):
 120             raise _OptionError("invalid lineno %r" % (lineno,))
 121     else:
 122         lineno = 0
 123     filterwarnings(action, message, category, module, lineno)
 124
 125 # Helper for _setoption()
 126 def _getaction(action):
 127     if not action:
 128         return "default"
 129     if action == "all": return "always" # Alias
 130     for a in ('default', 'always', 'ignore', 'module', 'once', 'error'):
 131         if a.startswith(action):
 132             return a
 133     raise _OptionError("invalid action: %r" % (action,))
 134
 135 # Helper for _setoption()
 136 def _getcategory(category):
 137     import re
 138     if not category:
 139         return Warning
 140     if re.match("^[a-zA-Z0-9_]+$", category):
 141         try:
 142             cat = eval(category)
 143         except NameError:
 144             raise _OptionError("unknown warning category: %r" % (category,))
 145     else:
 146         i = category.rfind(".")
 147         module = category[:i]
 148         klass = category[i+1:]
 149         try:
 150             m = __import__(module, None, None, [klass])
 151         except ImportError:
 152             raise _OptionError("invalid module name: %r" % (module,))
 153         try:
 154             cat = getattr(m, klass)
 155         except AttributeError:
 156             raise _OptionError("unknown warning category: %r" % (category,))
 157     if not issubclass(cat, Warning):
 158         raise _OptionError("invalid warning category: %r" % (category,))
 159     return cat
 160
 161
 162 # Code typically replaced by _warnings
 163 def warn(message, category=None, stacklevel=1):
 164     """Issue a warning, or maybe ignore it or raise an exception."""
 165     # Check if message is already a Warning object
 166     if isinstance(message, Warning):
 167         category = message.__class__
 168     # Check category argument
 169     if category is None:
 170         category = UserWarning
 171     assert issubclass(category, Warning)
 172     # Get context information
 173     try:
 174         caller = sys._getframe(stacklevel)
 175     except ValueError:
 176         globals = sys.__dict__
 177         lineno = 1
 178     else:
 179         globals = caller.f_globals
 180         lineno = caller.f_lineno
 181     if '__name__' in globals:
 182         module = globals['__name__']
 183     else:
 184         module = "<string>"
 185     filename = globals.get('__file__')
 186     if filename:
 187         fnl = filename.lower()
 188         if fnl.endswith((".pyc", ".pyo")):
 189             filename = filename[:-1]
 190     else:
 191         if module == "__main__":
 192             try:
 193                 filename = sys.argv[0]
 194             except AttributeError:
 195                 # embedded interpreters don't have sys.argv, see bug #839151
 196                 filename = '__main__'
 197         if not filename:
 198             filename = module
 199     registry = globals.setdefault("__warningregistry__", {})
 200     warn_explicit(message, category, filename, lineno, module, registry,
 201                   globals)
 202
 203 def warn_explicit(message, category, filename, lineno,
 204                   module=None, registry=None, module_globals=None):
 205     lineno = int(lineno)
 206     if module is None:
 207         module = filename or "<unknown>"
 208         if module[-3:].lower() == ".py":
 209             module = module[:-3] # XXX What about leading pathname?
 210     if registry is None:
 211         registry = {}
 212     if isinstance(message, Warning):
 213         text = str(message)
 214         category = message.__class__
 215     else:
 216         text = message
 217         message = category(message)
 218     key = (text, category, lineno)
 219     # Quick test for common case
 220     if registry.get(key):
 221         return
 222     # Search the filters
 223     for item in filters:
 224         action, msg, cat, mod, ln = item
 225         if ((msg is None or msg.match(text)) and
 226             issubclass(category, cat) and
 227             (mod is None or mod.match(module)) and
 228             (ln == 0 or lineno == ln)):
 229             break
 230     else:
 231         action = defaultaction
 232     # Early exit actions
 233     if action == "ignore":
 234         registry[key] = 1
 235         return
 236
 237     # Prime the linecache for formatting, in case the
 238     # "file" is actually in a zipfile or something.
 239     linecache.getlines(filename, module_globals)
 240
 241     if action == "error":
 242         raise message
 243     # Other actions
 244     if action == "once":
 245         registry[key] = 1
 246         oncekey = (text, category)
 247         if onceregistry.get(oncekey):
 248             return
 249         onceregistry[oncekey] = 1
 250     elif action == "always":
 251         pass
 252     elif action == "module":
 253         registry[key] = 1
 254         altkey = (text, category, 0)
 255         if registry.get(altkey):
 256             return
 257         registry[altkey] = 1
 258     elif action == "default":
 259         registry[key] = 1
 260     else:
 261         # Unrecognized actions are errors
 262         raise RuntimeError(
 263               "Unrecognized action (%r) in warnings.filters:\n %s" %
 264               (action, item))
 265     # Print message and context
 266     showwarning(message, category, filename, lineno)
 267
 268
 269 class WarningMessage(object):
 270
 271     """Holds the result of a single showwarning() call."""
 272
 273     _WARNING_DETAILS = ("message", "category", "filename", "lineno", "file",
 274                         "line")
 275
 276     def __init__(self, message, category, filename, lineno, file=None,
 277                     line=None):
 278         local_values = locals()
 279         for attr in self._WARNING_DETAILS:
 280             setattr(self, attr, local_values[attr])
 281         self._category_name = category.__name__ if category else None
 282
 283     def __str__(self):
 284         return ("{message : %r, category : %r, filename : %r, lineno : %s, "
 285                     "line : %r}" % (self.message, self._category_name,
 286                                     self.filename, self.lineno, self.line))
 287
 288
 289 class catch_warnings(object):
 290
 291     """A context manager that copies and restores the warnings filter upon
 292     exiting the context.
 293
 294     The 'record' argument specifies whether warnings should be captured by a
 295     custom implementation of warnings.showwarning() and be appended to a list
 296     returned by the context manager. Otherwise None is returned by the context
 297     manager. The objects appended to the list are arguments whose attributes
 298     mirror the arguments to showwarning().
 299
 300     The 'module' argument is to specify an alternative module to the module
 301     named 'warnings' and imported under that name. This argument is only useful
 302     when testing the warnings module itself.
 303
 304     """
 305
 306     def __init__(self, record=False, module=None):
 307         """Specify whether to record warnings and if an alternative module
 308         should be used other than sys.modules['warnings'].
 309
 310         For compatibility with Python 3.0, please consider all arguments to be
 311         keyword-only.
 312
 313         """
 314         self._record = record
 315         self._module = sys.modules['warnings'] if module is None else module
 316         self._entered = False
 317
 318     def __repr__(self):
 319         args = []
 320         if self._record:
 321             args.append("record=True")
 322         if self._module is not sys.modules['warnings']:
 323             args.append("module=%r" % self._module)
 324         name = type(self).__name__
 325         return "%s(%s)" % (name, ", ".join(args))
 326
 327     def __enter__(self):
 328         if self._entered:
 329             raise RuntimeError("Cannot enter %r twice" % self)
 330         self._entered = True
 331         self._filters = self._module.filters
 332         self._module.filters = self._filters[:]
 333         self._showwarning = self._module.showwarning
 334         if self._record:
 335             log = []
 336             def showwarning(*args, **kwargs):
 337                 log.append(WarningMessage(*args, **kwargs))
 338             self._module.showwarning = showwarning
 339             return log
 340         else:
 341             return None
 342
 343     def __exit__(self, *exc_info):
 344         if not self._entered:
 345             raise RuntimeError("Cannot exit %r without entering first" % self)
 346         self._module.filters = self._filters
 347         self._module.showwarning = self._showwarning
 348
 349
 350 # filters contains a sequence of filter 5-tuples
 351 # The components of the 5-tuple are:
 352 # - an action: error, ignore, always, default, module, or once
 353 # - a compiled regex that must match the warning message
 354 # - a class representing the warning category
 355 # - a compiled regex that must match the module that is being warned
 356 # - a line number for the line being warning, or 0 to mean any line
 357 # If either if the compiled regexs are None, match anything.
 358 _warnings_defaults = False
 359 try:
 360     from _warnings import (filters, default_action, once_registry,
 361                             warn, warn_explicit)
 362     defaultaction = default_action
 363     onceregistry = once_registry
 364     _warnings_defaults = True
 365 except ImportError:
 366     filters = []
 367     defaultaction = "default"
 368     onceregistry = {}
 369
 370
 371 # Module initialization
 372 _processoptions(sys.warnoptions)
 373 if not _warnings_defaults:
 374     simplefilter("ignore", category=PendingDeprecationWarning, append=1)
 375     simplefilter("ignore", category=ImportWarning, append=1)
 376     bytes_warning = sys.flags.bytes_warning
 377     if bytes_warning > 1:
 378         bytes_action = "error"
 379     elif bytes_warning:
 380         bytes_action = "default"
 381     else:
 382         bytes_action = "ignore"
 383     simplefilter(bytes_action, category=BytesWarning, append=1)
 384 del _warnings_defaults