Mercurial > hg
annotate mercurial/parser.py @ 13158:9e7e24052745
merge: fast-forward merge with descendant
issue2538 gives a case where a changeset is merged with its child (which is on
another branch), and to my surprise the result is a real merge with two
parents, not just a "fast forward" "merge" with only the child as parent.
That is essentially the same as issue619.
Is the existing behaviour as intended and correct?
Or is the following fix correct?
Some extra "created new head" pops up with this fix, but it seems to me like
they could be considered correct. The old branch head has been superseeded by
changes on the other branch, and when the changes on the other branch is merged
back to the branch it will introduce a new head not directly related to the
previous branch head.
(I guess the intention with existing behaviour could be to ensure that the
changesets on the branch are directly connected and that no new heads pops up
on merges.)
author | Mads Kiilerich <mads@kiilerich.com> |
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date | Tue, 07 Dec 2010 03:29:21 +0100 |
parents | 05af334bac05 |
children | 895f54a79c6e |
rev | line source |
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11274 | 1 # parser.py - simple top-down operator precedence parser for mercurial |
2 # | |
3 # Copyright 2010 Matt Mackall <mpm@selenic.com> | |
4 # | |
5 # This software may be used and distributed according to the terms of the | |
6 # GNU General Public License version 2 or any later version. | |
7 | |
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8 # see http://effbot.org/zone/simple-top-down-parsing.htm and |
11274 | 9 # http://eli.thegreenplace.net/2010/01/02/top-down-operator-precedence-parsing/ |
10 # for background | |
11 | |
12 # takes a tokenizer and elements | |
13 # tokenizer is an iterator that returns type, value pairs | |
14 # elements is a mapping of types to binding strength, prefix and infix actions | |
15 # an action is a tree node name, a tree label, and an optional match | |
16 # __call__(program) parses program into a labelled tree | |
17 | |
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18 import error |
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19 |
11274 | 20 class parser(object): |
21 def __init__(self, tokenizer, elements, methods=None): | |
22 self._tokenizer = tokenizer | |
23 self._elements = elements | |
24 self._methods = methods | |
25 def _advance(self): | |
26 'advance the tokenizer' | |
27 t = self.current | |
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28 try: |
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29 self.current = self._iter.next() |
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30 except StopIteration: |
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31 pass |
11274 | 32 return t |
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33 def _match(self, m, pos): |
11274 | 34 'make sure the tokenizer matches an end condition' |
35 if self.current[0] != m: | |
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36 raise error.ParseError("unexpected token: %s" % self.current[0], |
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37 self.current[2]) |
11274 | 38 self._advance() |
39 def _parse(self, bind=0): | |
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40 token, value, pos = self._advance() |
11274 | 41 # handle prefix rules on current token |
42 prefix = self._elements[token][1] | |
43 if not prefix: | |
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44 raise error.ParseError("not a prefix: %s" % token, pos) |
11274 | 45 if len(prefix) == 1: |
46 expr = (prefix[0], value) | |
47 else: | |
48 if len(prefix) > 2 and prefix[2] == self.current[0]: | |
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49 self._match(prefix[2], pos) |
11274 | 50 expr = (prefix[0], None) |
51 else: | |
52 expr = (prefix[0], self._parse(prefix[1])) | |
53 if len(prefix) > 2: | |
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54 self._match(prefix[2], pos) |
11274 | 55 # gather tokens until we meet a lower binding strength |
56 while bind < self._elements[self.current[0]][0]: | |
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57 token, value, pos = self._advance() |
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58 e = self._elements[token] |
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59 # check for suffix - next token isn't a valid prefix |
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60 if len(e) == 4 and not self._elements[self.current[0]][1]: |
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61 suffix = e[3] |
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62 expr = (suffix[0], expr) |
11274 | 63 else: |
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64 # handle infix rules |
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65 if len(e) < 3 or not e[2]: |
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66 raise error.ParseError("not an infix: %s" % token, pos) |
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67 infix = e[2] |
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68 if len(infix) == 3 and infix[2] == self.current[0]: |
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69 self._match(infix[2], pos) |
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70 expr = (infix[0], expr, (None)) |
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71 else: |
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72 expr = (infix[0], expr, self._parse(infix[1])) |
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73 if len(infix) == 3: |
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74 self._match(infix[2], pos) |
11274 | 75 return expr |
76 def parse(self, message): | |
77 'generate a parse tree from a message' | |
78 self._iter = self._tokenizer(message) | |
79 self.current = self._iter.next() | |
80 return self._parse() | |
81 def eval(self, tree): | |
82 'recursively evaluate a parse tree using node methods' | |
83 if not isinstance(tree, tuple): | |
84 return tree | |
85 return self._methods[tree[0]](*[self.eval(t) for t in tree[1:]]) | |
86 def __call__(self, message): | |
87 'parse a message into a parse tree and evaluate if methods given' | |
88 t = self.parse(message) | |
89 if self._methods: | |
90 return self.eval(t) | |
91 return t |