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# Copyright (C) 2006, 2009, 2010 Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
#
# Author: Martin Pool <mbp@canonical.com>
# Aaron Bentley <aaron.bentley@utoronto.ca>
from __future__ import absolute_import
from bzrlib.lazy_import import lazy_import
lazy_import(globals(), """
from bzrlib import patiencediff
""")
class TextMerge(object):
"""Base class for text-mergers
Subclasses must implement _merge_struct.
Many methods produce or consume structured merge information.
This is an iterable of tuples of lists of lines.
Each tuple may have a length of 1 - 3, depending on whether the region it
represents is conflicted.
Unconflicted region tuples have length 1.
Conflicted region tuples have length 2 or 3. Index 1 is text_a, e.g. THIS.
Index 1 is text_b, e.g. OTHER. Index 2 is optional. If present, it
represents BASE.
"""
# TODO: Show some version information (e.g. author, date) on conflicted
# regions.
A_MARKER = '<<<<<<< \n'
B_MARKER = '>>>>>>> \n'
SPLIT_MARKER = '=======\n'
def __init__(self, a_marker=A_MARKER, b_marker=B_MARKER,
split_marker=SPLIT_MARKER):
self.a_marker = a_marker
self.b_marker = b_marker
self.split_marker = split_marker
def _merge_struct(self):
"""Return structured merge info. Must be implemented by subclasses.
See TextMerge docstring for details on the format.
"""
raise NotImplementedError('_merge_struct is abstract')
def struct_to_lines(self, struct_iter):
"""Convert merge result tuples to lines"""
for lines in struct_iter:
if len(lines) == 1:
for line in lines[0]:
yield line
else:
yield self.a_marker
for line in lines[0]:
yield line
yield self.split_marker
for line in lines[1]:
yield line
yield self.b_marker
def iter_useful(self, struct_iter):
"""Iterate through input tuples, skipping empty ones."""
for group in struct_iter:
if len(group[0]) > 0:
yield group
elif len(group) > 1 and len(group[1]) > 0:
yield group
def merge_lines(self, reprocess=False):
"""Produce an iterable of lines, suitable for writing to a file
Returns a tuple of (line iterable, conflict indicator)
If reprocess is True, a two-way merge will be performed on the
intermediate structure, to reduce conflict regions.
"""
struct = []
conflicts = False
for group in self.merge_struct(reprocess):
struct.append(group)
if len(group) > 1:
conflicts = True
return self.struct_to_lines(struct), conflicts
def merge_struct(self, reprocess=False):
"""Produce structured merge info"""
struct_iter = self.iter_useful(self._merge_struct())
if reprocess is True:
return self.reprocess_struct(struct_iter)
else:
return struct_iter
@staticmethod
def reprocess_struct(struct_iter):
""" Perform a two-way merge on structural merge info.
This reduces the size of conflict regions, but breaks the connection
between the BASE text and the conflict region.
This process may split a single conflict region into several smaller
ones, but will not introduce new conflicts.
"""
for group in struct_iter:
if len(group) == 1:
yield group
else:
for newgroup in Merge2(group[0], group[1]).merge_struct():
yield newgroup
class Merge2(TextMerge):
""" Two-way merge.
In a two way merge, common regions are shown as unconflicting, and uncommon
regions produce conflicts.
"""
def __init__(self, lines_a, lines_b, a_marker=TextMerge.A_MARKER,
b_marker=TextMerge.B_MARKER,
split_marker=TextMerge.SPLIT_MARKER):
TextMerge.__init__(self, a_marker, b_marker, split_marker)
self.lines_a = lines_a
self.lines_b = lines_b
def _merge_struct(self):
"""Return structured merge info.
See TextMerge docstring.
"""
sm = patiencediff.PatienceSequenceMatcher(
None, self.lines_a, self.lines_b)
pos_a = 0
pos_b = 0
for ai, bi, l in sm.get_matching_blocks():
# non-matching lines
yield(self.lines_a[pos_a:ai], self.lines_b[pos_b:bi])
# matching lines
yield(self.lines_a[ai:ai+l],)
pos_a = ai + l
pos_b = bi + l
# final non-matching lines
yield(self.lines_a[pos_a:-1], self.lines_b[pos_b:-1])
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