view mercurial/parser.py @ 12998:91cb08a9e7fb

discovery: list new remote heads in prepush() on --debug

With this patch applied, Mercurial will list the hashes of new remote heads
if push --debug aborts because of new remote heads (option -f/--force not set).

Example:

  $ hg push --debug repo1
  using http://example.org/repo1
  http auth: user johndoe, password not set
  sending between command
  pushing to http://example.org/repo1
  sending capabilities command
  capabilities: changegroupsubset stream=1 lookup pushkey unbundle=HG10GZ,HG10BZ,HG10UN branchmap
  sending heads command
  searching for changes
  common changesets up to 609edbc7853f
  sending branchmap command
  new remote heads on branch 'default'        <- new output line
  new remote head 5862c07f53a2                <- new output line
  abort: push creates new remote heads on branch 'default'!
  (did you forget to merge? use push -f to force)

Compare to without --debug (not changed by this patch, including it here
for reference purposes only):

  $ hg push repo1
  pushing to http://example.org/repo1
  searching for changes
  abort: push creates new remote heads on branch 'default'!
  (did you forget to merge? use push -f to force)

Motivation for this change:

'hg outgoing' may list a whole lot of benign changesets plus an odd changeset
that will trigger the "new remote heads" abort. It can be hard to spot that
single unwanted changeset (it may be an old forgotten experiment, lingering
in the local repo).

"hg log -r 'heads(outgoing())'" might be useful, but that also lists a head
that may be benign on push.

Inside prepush(), we already know which heads are causing troubles on 'hg push'.
Why not make that info available (at least on --debug)?

This would also be helpful for doing remote support, as the supporter can ask
the user to paste the output of 'hg push --debug' on error and then ask further
questions about the heads listed.

# 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
    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.current = self._iter.next()
        return self._parse()
    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