view mercurial/parser.py @ 13950:14d0553bd48b

help: do not show full help text for command on option errors

Example

  $ hg clone --jump foo bar
  hg clone: option --jump not recognized
  hg clone [OPTION]... SOURCE [DEST]

  make a copy of an existing repository

  options:

   -U --noupdate           the clone will include an empty working copy (only a
                           repository)
   -u --updaterev REV      revision, tag or branch to check out
   -r --rev REV [+]        include the specified changeset
   -b --branch BRANCH [+]  clone only the specified branch
      --pull               use pull protocol to copy metadata
      --uncompressed       use uncompressed transfer (fast over LAN)
   -e --ssh CMD            specify ssh command to use
      --remotecmd CMD      specify hg command to run on the remote side
      --insecure           do not verify server certificate (ignoring
                           web.cacerts config)

  [+] marked option can be specified multiple times

  use "hg help clone" to show the full help text

Motivation for this change

  If the user already has specified the command, he probably already knows
  the command to some extent. Apparently, he has a problem with the options,
  so we show him just the synopsis with the short help and the details about
  the options, with a hint on the last line how to get the full help text.

Why is Mercurial better with this change?

  Experts who just forgot about the details of an option don't get that
  much text thrown at them, while the newbies still get a hint on the last
  line how to get the full help text.

# parser.py - simple top-down operator precedence parser for mercurial
#
# Copyright 2010 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

# see http://effbot.org/zone/simple-top-down-parsing.htm and
# http://eli.thegreenplace.net/2010/01/02/top-down-operator-precedence-parsing/
# for background

# takes a tokenizer and elements
# tokenizer is an iterator that returns type, value pairs
# elements is a mapping of types to binding strength, prefix and infix actions
# an action is a tree node name, a tree label, and an optional match
# __call__(program) parses program into a labelled tree

import error

class parser(object):
    def __init__(self, tokenizer, elements, methods=None):
        self._tokenizer = tokenizer
        self._elements = elements
        self._methods = methods
        self.current = None
    def _advance(self):
        'advance the tokenizer'
        t = self.current
        try:
            self.current = self._iter.next()
        except StopIteration:
            pass
        return t
    def _match(self, m, pos):
        'make sure the tokenizer matches an end condition'
        if self.current[0] != m:
            raise error.ParseError("unexpected token: %s" % self.current[0],
                                   self.current[2])
        self._advance()
    def _parse(self, bind=0):
        token, value, pos = self._advance()
        # handle prefix rules on current token
        prefix = self._elements[token][1]
        if not prefix:
            raise error.ParseError("not a prefix: %s" % token, pos)
        if len(prefix) == 1:
            expr = (prefix[0], value)
        else:
            if len(prefix) > 2 and prefix[2] == self.current[0]:
                self._match(prefix[2], pos)
                expr = (prefix[0], None)
            else:
                expr = (prefix[0], self._parse(prefix[1]))
                if len(prefix) > 2:
                    self._match(prefix[2], pos)
        # gather tokens until we meet a lower binding strength
        while bind < self._elements[self.current[0]][0]:
            token, value, pos = self._advance()
            e = self._elements[token]
            # check for suffix - next token isn't a valid prefix
            if len(e) == 4 and not self._elements[self.current[0]][1]:
                suffix = e[3]
                expr = (suffix[0], expr)
            else:
                # handle infix rules
                if len(e) < 3 or not e[2]:
                    raise error.ParseError("not an infix: %s" % token, pos)
                infix = e[2]
                if len(infix) == 3 and infix[2] == self.current[0]:
                    self._match(infix[2], pos)
                    expr = (infix[0], expr, (None))
                else:
                    expr = (infix[0], expr, self._parse(infix[1]))
                    if len(infix) == 3:
                        self._match(infix[2], pos)
        return expr
    def parse(self, message):
        'generate a parse tree from a message'
        self._iter = self._tokenizer(message)
        self._advance()
        res = self._parse()
        token, value, pos = self.current
        return res, pos
    def eval(self, tree):
        'recursively evaluate a parse tree using node methods'
        if not isinstance(tree, tuple):
            return tree
        return self._methods[tree[0]](*[self.eval(t) for t in tree[1:]])
    def __call__(self, message):
        'parse a message into a parse tree and evaluate if methods given'
        t = self.parse(message)
        if self._methods:
            return self.eval(t)
        return t