michael@0: # This Source Code Form is subject to the terms of the Mozilla Public
michael@0: # License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0: # file, You can obtain one at http://mozilla.org/MPL/2.0/.
michael@0: 
michael@0: import sys
michael@0: from contextlib import contextmanager
michael@0: 
michael@0: 
michael@0: class ErrorMessage(Exception):
michael@0:     '''Exception type raised from errors.error() and errors.fatal()'''
michael@0: 
michael@0: 
michael@0: class AccumulatedErrors(Exception):
michael@0:     '''Exception type raised from errors.accumulate()'''
michael@0: 
michael@0: 
michael@0: class ErrorCollector(object):
michael@0:     '''
michael@0:     Error handling/logging class. A global instance, errors, is provided for
michael@0:     convenience.
michael@0: 
michael@0:     Warnings, errors and fatal errors may be logged by calls to the following
michael@0:     functions:
michael@0:         errors.warn(message)
michael@0:         errors.error(message)
michael@0:         errors.fatal(message)
michael@0: 
michael@0:     Warnings only send the message on the logging output, while errors and
michael@0:     fatal errors send the message and throw an ErrorMessage exception. The
michael@0:     exception, however, may be deferred. See further below.
michael@0: 
michael@0:     Errors may be ignored by calling:
michael@0:         errors.ignore_errors()
michael@0: 
michael@0:     After calling that function, only fatal errors throw an exception.
michael@0: 
michael@0:     The warnings, errors or fatal errors messages may be augmented with context
michael@0:     information when a context is provided. Context is defined by a pair
michael@0:     (filename, linenumber), and may be set with errors.context() used as a
michael@0:     context manager:
michael@0:         with errors.context(filename, linenumber):
michael@0:             errors.warn(message)
michael@0: 
michael@0:     Arbitrary nesting is supported, both for errors.context calls:
michael@0:         with errors.context(filename1, linenumber1):
michael@0:             errors.warn(message)
michael@0:             with errors.context(filename2, linenumber2):
michael@0:                 errors.warn(message)
michael@0: 
michael@0:     as well as for function calls:
michael@0:         def func():
michael@0:             errors.warn(message)
michael@0:         with errors.context(filename, linenumber):
michael@0:             func()
michael@0: 
michael@0:     Errors and fatal errors can have their exception thrown at a later time,
michael@0:     allowing for several different errors to be reported at once before
michael@0:     throwing. This is achieved with errors.accumulate() as a context manager:
michael@0:         with errors.accumulate():
michael@0:             if test1:
michael@0:                 errors.error(message1)
michael@0:             if test2:
michael@0:                 errors.error(message2)
michael@0: 
michael@0:     In such cases, a single AccumulatedErrors exception is thrown, but doesn't
michael@0:     contain information about the exceptions. The logged messages do.
michael@0:     '''
michael@0:     out = sys.stderr
michael@0:     WARN = 1
michael@0:     ERROR = 2
michael@0:     FATAL = 3
michael@0:     _level = ERROR
michael@0:     _context = []
michael@0:     _count = None
michael@0: 
michael@0:     def ignore_errors(self, ignore=True):
michael@0:         if ignore:
michael@0:             self._level = self.FATAL
michael@0:         else:
michael@0:             self._level = self.ERROR
michael@0: 
michael@0:     def _full_message(self, level, msg):
michael@0:         if level >= self._level:
michael@0:             level = 'Error'
michael@0:         else:
michael@0:             level = 'Warning'
michael@0:         if self._context:
michael@0:             file, line = self._context[-1]
michael@0:             return "%s: %s:%d: %s" % (level, file, line, msg)
michael@0:         return "%s: %s" % (level, msg)
michael@0: 
michael@0:     def _handle(self, level, msg):
michael@0:         msg = self._full_message(level, msg)
michael@0:         if level >= self._level:
michael@0:             if self._count is None:
michael@0:                 raise ErrorMessage(msg)
michael@0:             self._count += 1
michael@0:         print >>self.out, msg
michael@0: 
michael@0:     def fatal(self, msg):
michael@0:         self._handle(self.FATAL, msg)
michael@0: 
michael@0:     def error(self, msg):
michael@0:         self._handle(self.ERROR, msg)
michael@0: 
michael@0:     def warn(self, msg):
michael@0:         self._handle(self.WARN, msg)
michael@0: 
michael@0:     def get_context(self):
michael@0:         if self._context:
michael@0:             return self._context[-1]
michael@0: 
michael@0:     @contextmanager
michael@0:     def context(self, file, line):
michael@0:         if file and line:
michael@0:             self._context.append((file, line))
michael@0:         yield
michael@0:         if file and line:
michael@0:             self._context.pop()
michael@0: 
michael@0:     @contextmanager
michael@0:     def accumulate(self):
michael@0:         assert self._count is None
michael@0:         self._count = 0
michael@0:         yield
michael@0:         count = self._count
michael@0:         self._count = None
michael@0:         if count:
michael@0:             raise AccumulatedErrors()
michael@0: 
michael@0:     @property
michael@0:     def count(self):
michael@0:         # _count can be None.
michael@0:         return self._count if self._count else 0
michael@0: 
michael@0: 
michael@0: errors = ErrorCollector()