# vim: set et sts=4 sw=4 encoding=utf-8 :
-r"""
-Command dispatcher.
+r"""Command dispatcher.
This module provides a convenient and extensible command dispatching mechanism.
It's based on Zope or Cherrypy dispatching (but implemented from the scratch)
and translates commands to functions/objects/methods.
"""
+__ALL__ = ('Error', 'HandlerError', 'CommandNotFoundError', 'Handler',
+ 'Dispatcher', 'handler', 'is_handler', 'get_help')
+
class Error(RuntimeError):
- r"""
- Error(command) -> Error instance :: Base dispatching exceptions class.
+ r"""Error(command) -> Error instance :: Base dispatching exceptions class.
All exceptions raised by the Dispatcher inherits from this one, so you can
easily catch any dispatching exception.
command - is the command that raised the exception, expressed as a list of
paths (or subcommands).
"""
+ pass
+
+class HandlerError(Error):
+ r"""HandlerError(command) -> HandlerError instance :: Base handlers error.
+
+ All exceptions raised by the handlers should inherit from this one, so
+ dispatching errors could be separated from real programming errors (bugs).
+ """
+ pass
+
+class CommandError(Error):
+ r"""CommandError(command) -> CommandError instance :: Base command error.
+
+ This exception is raised when there's a problem with the command itself.
+ It's the base class for all command (as a string) related error.
+ """
def __init__(self, command):
- r"""Initialize the Error object.
+ r"""Initialize the object.
- See Error class documentation for more info.
+ See class documentation for more info.
"""
self.command = command
def __str__(self):
- return ' '.join(self.command)
+ return 'Command error: "%s"' % self.command
-class CommandNotFoundError(Error):
- r"""
- CommandNotFoundError(command) -> CommandNotFoundError instance
+class CommandNotFoundError(CommandError):
+ r"""CommandNotFoundError(command) -> CommandNotFoundError instance.
This exception is raised when the command received can't be dispatched
because there is no handlers to process it.
"""
- pass
-def handler(f):
- f._dispatcher_handler = True
- return f
+ def __str__(self):
+ return 'Command not found: "%s"' % ' '.join(
+ repr(c) for c in self.command)
+
+class ParseError(CommandError):
+ r"""ParseError(command[, desc]) -> ParseError instance
+
+ This exception is raised when there is an error parsing a command.
+
+ command - Command that can't be parsed.
+
+ desc - Description of the error.
+ """
+
+ def __init__(self, command, desc="can't parse"):
+ r"""Initialize the object.
+
+ See class documentation for more info.
+ """
+ self.command = command
+ self.desc = desc
+
+ def __str__(self):
+ return 'Syntax error, %s: %s' % (self.desc, self.command)
+
+def handler(help):
+ r"""handler(help) -> function wrapper :: Mark a callable as a handler.
+
+ This is a decorator to mark a callable object as a dispatcher handler.
+
+ help - Help string for the handler.
+ """
+ def wrapper(f):
+ if not help:
+ raise TypeError("'help' should not be empty")
+ f._dispatcher_help = help
+ return f
+ return wrapper
def is_handler(handler):
- return callable(handler) and hasattr(handler, '_dispatcher_handler') \
- and handler._dispatcher_handler
+ r"is_handler(handler) -> bool :: Tell if a object is a handler."
+ return callable(handler) and hasattr(handler, '_dispatcher_help')
+
+def get_help(handler):
+ r"get_help(handler) -> unicode :: Get a handler's help string."
+ if not is_handler(handler):
+ raise TypeError("'%s' should be a handler" % handler.__name__)
+ return handler._dispatcher_help
+
+class Handler:
+ r"""Handler() -> Handler instance :: Base class for all dispatcher handlers.
+
+ All dispatcher handlers should inherit from this class to have some extra
+ commands, like help.
+ """
+
+ @handler(u'List available commands.')
+ def commands(self):
+ r"""commands() -> generator :: List the available commands."""
+ return (a for a in dir(self) if is_handler(getattr(self, a)))
+
+ @handler(u'Show available commands with their help.')
+ def help(self, command=None):
+ r"""help([command]) -> unicode/dict :: Show help on available commands.
+
+ If command is specified, it returns the help of that particular command.
+ If not, it returns a dictionary which keys are the available commands
+ and values are the help strings.
+ """
+ if command is None:
+ return dict((a, get_help(getattr(self, a)))
+ for a in dir(self) if is_handler(getattr(self, a)))
+ if not hasattr(self, command):
+ raise CommandNotFoundError(command)
+ handler = getattr(self, command)
+ if not is_handler(handler):
+ raise CommandNotFoundError(command)
+ return get_help(handler)
+
+def parse_command(command):
+ r"""parse_command(command) -> (args, kwargs) :: Parse a command.
+
+ This function parses a command and split it into a list of parameters. It
+ has a similar to bash commandline parser. Spaces are the basic token
+ separator but you can group several tokens into one by using (single or
+ double) quotes. You can escape the quotes with a backslash (\' and \"),
+ express a backslash literal using a double backslash (\\), use special
+ meaning escaped sequences (like \a, \n, \r, \b, \v) and use unescaped
+ single quotes inside a double quoted token or vice-versa. A special escape
+ sequence is provided to express a NULL/None value: \N and it should appear
+ always as a separated token.
+
+ Additionally it accepts keyword arguments. When an (not-escaped) equal
+ sign (=) is found, the argument is considered a keyword, and the next
+ argument it's interpreted as its value.
+
+ This function returns a tuple containing a list and a dictionary. The
+ first has the positional arguments, the second, the keyword arguments.
+
+ There is no restriction about the order, a keyword argument can be
+ followed by a positional argument and vice-versa. All type of arguments
+ are grouped in the list/dict returned. The order of the positional
+ arguments is preserved and if there are multiple keyword arguments with
+ the same key, the last value is the winner (all other values are lost).
+
+ Examples:
+
+ >>> parse_command('hello world')
+ ([u'hello', u'world'], {})
+ >>> parse_command('hello planet=earth')
+ ([u'hello'], {'planet': u'earth'})
+ >>> parse_command('hello planet="third rock from the sun"')
+ ([u'hello'], {'planet': u'third rock from the sun'})
+ >>> parse_command(u' planet="third rock from the sun" hello ')
+ ([u'hello'], {'planet': u'third rock from the sun'})
+ >>> parse_command(u' planet="third rock from the sun" "hi, hello"'
+ '"how are you" ')
+ ([u'hi, hello', u'how are you'], {'planet': u'third rock from the sun'})
+ >>> parse_command(u'one two three "fourth number"=four')
+ ([u'one', u'two', u'three'], {'fourth number': u'four'})
+ >>> parse_command(u'one two three "fourth number=four"')
+ ([u'one', u'two', u'three', u'fourth number=four'], {})
+ >>> parse_command(u'one two three fourth\=four')
+ ([u'one', u'two', u'three', u'fourth=four'], {})
+ >>> parse_command(u'one two three fourth=four=five')
+ ([u'one', u'two', u'three'], {'fourth': u'four=five'})
+ >>> parse_command(ur'nice\nlong\n\ttext')
+ ([u'nice\nlong\n\ttext'], {})
+ >>> parse_command('=hello')
+ ([u'=hello'], {})
+ >>> parse_command(r'\thello')
+ ([u'\thello'], {})
+ >>> parse_command(r'\N')
+ ([None], {})
+ >>> parse_command(r'none=\N')
+ ([], {'none': None})
+ >>> parse_command(r'\N=none')
+ ([], {'\\N': 'none'})
+ >>> parse_command(r'Not\N')
+ ([u'Not\\N'], {})
+ >>> parse_command(r'\None')
+ ([u'\\None'], {})
+
+ This examples are syntax errors:
+ Missing quote: "hello world
+ Missing value: hello=
+ """
+ SEP, TOKEN, DQUOTE, SQUOTE, EQUAL = u' ', None, u'"', u"'", u'=' # states
+ separators = (u' ', u'\t', u'\v', u'\n') # token separators
+ escaped_chars = (u'a', u'n', u'r', u'b', u'v', u't') # escaped sequences
+ seq = []
+ dic = {}
+ buff = u''
+ escape = False
+ keyword = None
+ state = SEP
+ for n, c in enumerate(command):
+ # Escaped character
+ if escape:
+ for e in escaped_chars:
+ if c == e:
+ buff += eval(u'"\\' + e + u'"')
+ break
+ else:
+ if c == 'N':
+ buff += r'\N'
+ else:
+ buff += c
+ escape = False
+ continue
+ # Escaped sequence start
+ if c == u'\\':
+ escape = True
+ continue
+ # Looking for spaces
+ if state == SEP:
+ if c in separators:
+ continue
+ if buff and n != 2: # Not the first item (even if was a escape seq)
+ if c == EQUAL: # Keyword found
+ keyword = buff
+ buff = u''
+ continue
+ if buff == r'\N':
+ buff = None
+ if keyword is not None: # Value found
+ dic[str(keyword)] = buff
+ keyword = None
+ else: # Normal parameter found
+ seq.append(buff)
+ buff = u''
+ state = TOKEN
+ # Getting a token
+ if state == TOKEN:
+ if c == DQUOTE:
+ state = DQUOTE
+ continue
+ if c == SQUOTE:
+ state = SQUOTE
+ continue
+ # Check if a keyword is added
+ if c == EQUAL and keyword is None and buff:
+ keyword = buff
+ buff = u''
+ state = SEP
+ continue
+ if c in separators:
+ state = SEP
+ continue
+ buff += c
+ continue
+ # Inside a double quote
+ if state == DQUOTE:
+ if c == DQUOTE:
+ state = TOKEN
+ continue
+ buff += c
+ continue
+ # Inside a single quote
+ if state == SQUOTE:
+ if c == SQUOTE:
+ state = TOKEN
+ continue
+ buff += c
+ continue
+ assert 0, u'Unexpected state'
+ if state == DQUOTE or state == SQUOTE:
+ raise ParseError(command, u'missing closing quote (%s)' % state)
+ if not buff and keyword is not None:
+ raise ParseError(command,
+ u'keyword argument (%s) without value' % keyword)
+ if buff:
+ if buff == r'\N':
+ buff = None
+ if keyword is not None:
+ dic[str(keyword)] = buff
+ else:
+ seq.append(buff)
+ return (seq, dic)
class Dispatcher:
r"""Dispatcher([routes]) -> Dispatcher instance :: Command dispatcher
Example:
>>> d = Dispatcher(dict(handler=some_handler))
- >>> d.dispatch('handler attribute method arg1 arg2')
+ >>> d.dispatch('handler attribute method arg1 arg2 "third argument"')
If 'some_handler' is an object with an 'attribute' that is another
object which has a method named 'method', then
can't be dispatched.
"""
command = list()
- route = route.split() # TODO support "" and keyword arguments
+ (route, kwargs) = parse_command(route)
if not route:
raise CommandNotFoundError(command)
command.append(route[0])
raise CommandNotFoundError(command)
handler = getattr(handler, route[0])
route = route[1:]
- handler(*route)
+ return handler(*route, **kwargs)
if __name__ == '__main__':
- @handler
+ @handler(u"test: Print all the arguments, return nothing.")
def test_func(*args):
- print 'func:', args
+ print 'func:', args
- class TestClassSubHandler:
- @handler
+ class TestClassSubHandler(Handler):
+ @handler(u"subcmd: Print all the arguments, return nothing.")
def subcmd(self, *args):
print 'class.subclass.subcmd:', args
- class TestClass:
- @handler
+ class TestClass(Handler):
+ @handler(u"cmd1: Print all the arguments, return nothing.")
def cmd1(self, *args):
print 'class.cmd1:', args
- @handler
+ @handler(u"cmd2: Print all the arguments, return nothing.")
def cmd2(self, *args):
print 'class.cmd2:', args
subclass = TestClassSubHandler()
+ test_class = TestClass()
+
d = Dispatcher(dict(
func=test_func,
- inst=TestClass(),
+ inst=test_class,
))
- d.dispatch('func arg1 arg2 arg3')
+ d.dispatch(r'''func arg1 arg2 arg3 "fourth 'argument' with \", a\ttab and\n\\n"''')
+ print 'inst commands:', tuple(d.dispatch('inst commands'))
+ print 'inst help:', d.dispatch('inst help')
d.dispatch('inst cmd1 arg1 arg2 arg3 arg4')
+ d.dispatch('inst cmd2 arg1 arg2')
+ print 'inst subclass help:', d.dispatch('inst subclass help')
d.dispatch('inst subclass subcmd arg1 arg2 arg3 arg4 arg5')
try:
d.dispatch('')
except CommandNotFoundError, e:
print 'Not found:', e
+ # Parser tests
+ p = parse_command('hello world')
+ assert p == ([u'hello', u'world'], {}), p
+ p = parse_command('hello planet=earth')
+ assert p == ([u'hello'], {'planet': u'earth'}), p
+ p = parse_command('hello planet="third rock from the sun"')
+ assert p == ([u'hello'], {'planet': u'third rock from the sun'}), p
+ p = parse_command(u' planet="third rock from the sun" hello ')
+ assert p == ([u'hello'], {'planet': u'third rock from the sun'}), p
+ p = parse_command(u' planet="third rock from the sun" "hi, hello" '
+ '"how are you" ')
+ assert p == ([u'hi, hello', u'how are you'],
+ {'planet': u'third rock from the sun'}), p
+ p = parse_command(u'one two three "fourth number"=four')
+ assert p == ([u'one', u'two', u'three'], {'fourth number': u'four'}), p
+ p = parse_command(u'one two three "fourth number=four"')
+ assert p == ([u'one', u'two', u'three', u'fourth number=four'], {}), p
+ p = parse_command(u'one two three fourth\=four')
+ assert p == ([u'one', u'two', u'three', u'fourth=four'], {}), p
+ p = parse_command(u'one two three fourth=four=five')
+ assert p == ([u'one', u'two', u'three'], {'fourth': u'four=five'}), p
+ p = parse_command(ur'nice\nlong\n\ttext')
+ assert p == ([u'nice\nlong\n\ttext'], {}), p
+ p = parse_command('=hello')
+ assert p == ([u'=hello'], {}), p
+ p = parse_command(r'\thello')
+ assert p == ([u'\thello'], {}), p
+ p = parse_command(r'\N')
+ assert p == ([None], {}), p
+ p = parse_command(r'none=\N')
+ assert p == ([], {'none': None}), p
+ p = parse_command(r'\N=none')
+ assert p == ([], {'\\N': 'none'}), p
+ p = parse_command(r'Not\N')
+ assert p == ([u'Not\\N'], {}), p
+ p = parse_command(r'\None')
+ assert p == ([u'\\None'], {}), p
+ try:
+ p = parse_command('hello=')
+ except ParseError, e:
+ pass
+ else:
+ assert False, p + ' should raised a ParseError'
+ try:
+ p = parse_command('"hello')
+ except ParseError, e:
+ pass
+ else:
+ assert False, p + ' should raised a ParseError'
+
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