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380 lines
11 KiB
380 lines
11 KiB
4 years ago
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#!/usr/bin/env python
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# Copyright 2003 Google Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS-IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Generic entry point for Google applications.
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To use this module, simply define a 'main' function with a single
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'argv' argument and add the following to the end of your source file:
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if __name__ == '__main__':
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app.run()
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TODO(user): Remove silly main-detection logic, and force all clients
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of this module to check __name__ explicitly. Fix all current clients
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that don't check __name__.
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"""
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import errno
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import os
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import pdb
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import socket
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import stat
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import struct
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import sys
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import time
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import traceback
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import gflags as flags
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FLAGS = flags.FLAGS
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flags.DEFINE_boolean('run_with_pdb', 0, 'Set to true for PDB debug mode')
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flags.DEFINE_boolean('pdb_post_mortem', 0,
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'Set to true to handle uncaught exceptions with PDB '
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'post mortem.')
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flags.DEFINE_boolean('run_with_profiling', 0,
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'Set to true for profiling the script. '
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'Execution will be slower, and the output format might '
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'change over time.')
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flags.DEFINE_string('profile_file', None,
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'Dump profile information to a file (for python -m '
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'pstats). Implies --run_with_profiling.')
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flags.DEFINE_boolean('use_cprofile_for_profiling', True,
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'Use cProfile instead of the profile module for '
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'profiling. This has no effect unless '
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'--run_with_profiling is set.')
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# If main() exits via an abnormal exception, call into these
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# handlers before exiting.
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EXCEPTION_HANDLERS = []
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help_text_wrap = False # Whether to enable TextWrap in help output
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class Error(Exception):
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pass
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class UsageError(Error):
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"""The arguments supplied by the user are invalid.
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Raise this when the arguments supplied are invalid from the point of
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view of the application. For example when two mutually exclusive
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flags have been supplied or when there are not enough non-flag
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arguments. It is distinct from flags.FlagsError which covers the lower
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level of parsing and validating individual flags.
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"""
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def __init__(self, message, exitcode=1):
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Error.__init__(self, message)
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self.exitcode = exitcode
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class HelpFlag(flags.BooleanFlag):
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"""Special boolean flag that displays usage and raises SystemExit."""
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NAME = 'help'
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def __init__(self):
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flags.BooleanFlag.__init__(self, self.NAME, 0, 'show this help',
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short_name='?', allow_override=1)
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def Parse(self, arg):
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if arg:
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usage(shorthelp=1, writeto_stdout=1)
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# Advertise --helpfull on stdout, since usage() was on stdout.
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print
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print 'Try --helpfull to get a list of all flags.'
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sys.exit(1)
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class HelpshortFlag(HelpFlag):
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"""--helpshort is an alias for --help."""
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NAME = 'helpshort'
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class HelpfullFlag(flags.BooleanFlag):
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"""Display help for flags in this module and all dependent modules."""
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def __init__(self):
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flags.BooleanFlag.__init__(self, 'helpfull', 0, 'show full help',
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allow_override=1)
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def Parse(self, arg):
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if arg:
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usage(writeto_stdout=1)
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sys.exit(1)
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class HelpXMLFlag(flags.BooleanFlag):
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"""Similar to HelpfullFlag, but generates output in XML format."""
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def __init__(self):
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flags.BooleanFlag.__init__(self, 'helpxml', False,
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'like --helpfull, but generates XML output',
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allow_override=1)
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def Parse(self, arg):
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if arg:
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flags.FLAGS.WriteHelpInXMLFormat(sys.stdout)
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sys.exit(1)
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class BuildDataFlag(flags.BooleanFlag):
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"""Boolean flag that writes build data to stdout and exits."""
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def __init__(self):
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flags.BooleanFlag.__init__(self, 'show_build_data', 0,
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'show build data and exit')
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def Parse(self, arg):
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if arg:
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sys.stdout.write(build_data.BuildData())
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sys.exit(0)
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def parse_flags_with_usage(args):
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"""Try parsing the flags, printing usage and exiting if unparseable."""
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try:
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argv = FLAGS(args)
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return argv
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except flags.FlagsError, error:
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sys.stderr.write('FATAL Flags parsing error: %s\n' % error)
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sys.stderr.write('Pass --helpshort or --helpfull to see help on flags.\n')
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sys.exit(1)
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_define_help_flags_called = False
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def DefineHelpFlags():
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"""Register help flags. Idempotent."""
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# Use a global to ensure idempotence.
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# pylint: disable=global-statement
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global _define_help_flags_called
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if not _define_help_flags_called:
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flags.DEFINE_flag(HelpFlag())
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flags.DEFINE_flag(HelpshortFlag()) # alias for --help
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flags.DEFINE_flag(HelpfullFlag())
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flags.DEFINE_flag(HelpXMLFlag())
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flags.DEFINE_flag(BuildDataFlag())
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_define_help_flags_called = True
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def RegisterAndParseFlagsWithUsage():
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"""Register help flags, parse arguments and show usage if appropriate.
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Returns:
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remaining arguments after flags parsing
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"""
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DefineHelpFlags()
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argv = parse_flags_with_usage(sys.argv)
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return argv
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def really_start(main=None):
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"""Initializes flag values, and calls main with non-flag arguments.
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Only non-flag arguments are passed to main(). The return value of main() is
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used as the exit status.
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Args:
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main: Main function to run with the list of non-flag arguments, or None
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so that sys.modules['__main__'].main is to be used.
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"""
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argv = RegisterAndParseFlagsWithUsage()
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if main is None:
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main = sys.modules['__main__'].main
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try:
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if FLAGS.run_with_pdb:
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sys.exit(pdb.runcall(main, argv))
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else:
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if FLAGS.run_with_profiling or FLAGS.profile_file:
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# Avoid import overhead since most apps (including performance-sensitive
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# ones) won't be run with profiling.
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import atexit
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if FLAGS.use_cprofile_for_profiling:
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import cProfile as profile
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else:
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import profile
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profiler = profile.Profile()
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if FLAGS.profile_file:
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atexit.register(profiler.dump_stats, FLAGS.profile_file)
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else:
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atexit.register(profiler.print_stats)
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retval = profiler.runcall(main, argv)
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sys.exit(retval)
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else:
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sys.exit(main(argv))
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except UsageError, error:
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usage(shorthelp=1, detailed_error=error, exitcode=error.exitcode)
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except:
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if FLAGS.pdb_post_mortem:
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traceback.print_exc()
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pdb.post_mortem()
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raise
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def run():
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"""Begin executing the program.
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- Parses command line flags with the flag module.
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- If there are any errors, print usage().
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- Calls main() with the remaining arguments.
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- If main() raises a UsageError, print usage and the error message.
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"""
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return _actual_start()
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def _actual_start():
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"""Another layer in the starting stack."""
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# Get raw traceback
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tb = None
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try:
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raise ZeroDivisionError('')
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except ZeroDivisionError:
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tb = sys.exc_info()[2]
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assert tb
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# Look at previous stack frame's previous stack frame (previous
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# frame is run() or start(); the frame before that should be the
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# frame of the original caller, which should be __main__ or appcommands
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prev_prev_frame = tb.tb_frame.f_back.f_back
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if not prev_prev_frame:
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return
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prev_prev_name = prev_prev_frame.f_globals.get('__name__', None)
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if (prev_prev_name != '__main__'
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and not prev_prev_name.endswith('.appcommands')):
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return
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# just in case there's non-trivial stuff happening in __main__
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del tb
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if hasattr(sys, 'exc_clear'):
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sys.exc_clear() # This functionality is gone in Python 3.
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try:
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really_start()
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except SystemExit, e:
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raise
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except Exception, e:
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# Call any installed exception handlers which may, for example,
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# log to a file or send email.
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for handler in EXCEPTION_HANDLERS:
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try:
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if handler.Wants(e):
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handler.Handle(e)
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except:
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# We don't want to stop for exceptions in the exception handlers but
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# we shouldn't hide them either.
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sys.stderr.write(traceback.format_exc())
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raise
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# All handlers have had their chance, now die as we would have normally.
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raise
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def usage(shorthelp=0, writeto_stdout=0, detailed_error=None, exitcode=None):
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"""Write __main__'s docstring to stderr with some help text.
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Args:
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shorthelp: print only flags from this module, rather than all flags.
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writeto_stdout: write help message to stdout, rather than to stderr.
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detailed_error: additional detail about why usage info was presented.
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exitcode: if set, exit with this status code after writing help.
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"""
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if writeto_stdout:
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stdfile = sys.stdout
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else:
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stdfile = sys.stderr
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doc = sys.modules['__main__'].__doc__
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if not doc:
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doc = '\nUSAGE: %s [flags]\n' % sys.argv[0]
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doc = flags.TextWrap(doc, indent=' ', firstline_indent='')
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else:
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# Replace all '%s' with sys.argv[0], and all '%%' with '%'.
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num_specifiers = doc.count('%') - 2 * doc.count('%%')
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try:
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doc %= (sys.argv[0],) * num_specifiers
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except (OverflowError, TypeError, ValueError):
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# Just display the docstring as-is.
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pass
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if help_text_wrap:
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doc = flags.TextWrap(flags.DocToHelp(doc))
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if shorthelp:
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flag_str = FLAGS.MainModuleHelp()
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else:
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flag_str = str(FLAGS)
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try:
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stdfile.write(doc)
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if flag_str:
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stdfile.write('\nflags:\n')
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stdfile.write(flag_str)
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stdfile.write('\n')
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if detailed_error is not None:
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stdfile.write('\n%s\n' % detailed_error)
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except IOError, e:
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# We avoid printing a huge backtrace if we get EPIPE, because
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# "foo.par --help | less" is a frequent use case.
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if e.errno != errno.EPIPE:
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raise
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if exitcode is not None:
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sys.exit(exitcode)
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class ExceptionHandler(object):
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"""Base exception handler from which other may inherit."""
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def Wants(self, unused_exc):
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"""Check if this exception handler want to handle this exception.
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Args:
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unused_exc: Exception, the current exception
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Returns:
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boolean
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This base handler wants to handle all exceptions, override this
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method if you want to be more selective.
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"""
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return True
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def Handle(self, exc):
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"""Do something with the current exception.
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Args:
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exc: Exception, the current exception
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This method must be overridden.
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"""
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raise NotImplementedError()
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def InstallExceptionHandler(handler):
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"""Install an exception handler.
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Args:
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handler: an object conforming to the interface defined in ExceptionHandler
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Raises:
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TypeError: handler was not of the correct type
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All installed exception handlers will be called if main() exits via
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an abnormal exception, i.e. not one of SystemExit, KeyboardInterrupt,
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FlagsError or UsageError.
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"""
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if not isinstance(handler, ExceptionHandler):
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raise TypeError('handler of type %s does not inherit from ExceptionHandler'
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% type(handler))
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EXCEPTION_HANDLERS.append(handler)
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