tests: fix test-bdiff to handle variance between pure and c bdiff code

Obviously we'd rather patch pure to have the same algorithmic win as
the C code, but this is a quick fix for the pure build since pure
isn't wrong, just not as fast as it could be.

tests/test-bdiff.py

@@ -1,141 +1,151 b''
 from __future__ import absolute_import, print_function
 import collections
 import struct
 import unittest
 
 import silenttestrunner
 
 from mercurial import (
     bdiff,
     mpatch,
 )
 
 class diffreplace(
     collections.namedtuple('diffreplace', 'start end from_ to')):
     def __repr__(self):
         return 'diffreplace(%r, %r, %r, %r)' % self
 
 class BdiffTests(unittest.TestCase):
 
     def assert_bdiff_applies(self, a, b):
         d = bdiff.bdiff(a, b)
         c = a
         if d:
             c = mpatch.patches(a, [d])
         self.assertEqual(
             c, b, ("bad diff+patch result from\n  %r to\n  "
                    "%r: \nbdiff: %r\npatched: %r" % (a, b, d, c[:200])))
 
     def assert_bdiff(self, a, b):
         self.assert_bdiff_applies(a, b)
         self.assert_bdiff_applies(b, a)
 
     def test_bdiff_basic(self):
         cases = [
             ("a\nc\n\n\n\n", "a\nb\n\n\n"),
             ("a\nb\nc\n", "a\nc\n"),
             ("", ""),
             ("a\nb\nc", "a\nb\nc"),
             ("a\nb\nc\nd\n", "a\nd\n"),
             ("a\nb\nc\nd\n", "a\nc\ne\n"),
             ("a\nb\nc\n", "a\nc\n"),
             ("a\n", "c\na\nb\n"),
             ("a\n", ""),
             ("a\n", "b\nc\n"),
             ("a\n", "c\na\n"),
             ("", "adjfkjdjksdhfksj"),
             ("", "ab"),
             ("", "abc"),
             ("a", "a"),
             ("ab", "ab"),
             ("abc", "abc"),
             ("a\n", "a\n"),
             ("a\nb", "a\nb"),
         ]
         for a, b in cases:
             self.assert_bdiff(a, b)
 
     def showdiff(self, a, b):
         bin = bdiff.bdiff(a, b)
         pos = 0
         q = 0
         actions = []
         while pos < len(bin):
             p1, p2, l = struct.unpack(">lll", bin[pos:pos + 12])
             pos += 12
             if p1:
                 actions.append(a[q:p1])
             actions.append(diffreplace(p1, p2, a[p1:p2], bin[pos:pos + l]))
             pos += l
             q = p2
         if q < len(a):
             actions.append(a[q:])
         return actions
 
     def test_issue1295(self):
         cases = [
             ("x\n\nx\n\nx\n\nx\n\nz\n", "x\n\nx\n\ny\n\nx\n\nx\n\nz\n",
              ['x\n\nx\n\n', diffreplace(6, 6, '', 'y\n\n'), 'x\n\nx\n\nz\n']),
             ("x\n\nx\n\nx\n\nx\n\nz\n", "x\n\nx\n\ny\n\nx\n\ny\n\nx\n\nz\n",
              ['x\n\nx\n\n',
               diffreplace(6, 6, '', 'y\n\n'),
               'x\n\n',
               diffreplace(9, 9, '', 'y\n\n'),
               'x\n\nz\n']),
+        ]
+        for old, new, want in cases:
+            self.assertEqual(self.showdiff(old, new), want)
+
+    def test_issue1295_varies_on_pure(self):
             # we should pick up abbbc. rather than bc.de as the longest match
-            ("a\nb\nb\nb\nc\n.\nd\ne\n.\nf\n",
-             "a\nb\nb\na\nb\nb\nb\nc\n.\nb\nc\n.\nd\ne\nf\n",
-             ['a\nb\nb\n',
+        got = self.showdiff("a\nb\nb\nb\nc\n.\nd\ne\n.\nf\n",
+                            "a\nb\nb\na\nb\nb\nb\nc\n.\nb\nc\n.\nd\ne\nf\n")
+        want_c = ['a\nb\nb\n',
               diffreplace(6, 6, '', 'a\nb\nb\nb\nc\n.\n'),
               'b\nc\n.\nd\ne\n',
               diffreplace(16, 18, '.\n', ''),
-              'f\n']),
-        ]
-        for old, new, want in cases:
-            self.assertEqual(self.showdiff(old, new), want)
+                  'f\n']
+        want_pure = [diffreplace(0, 0, '', 'a\nb\nb\n'),
+                     'a\nb\nb\nb\nc\n.\n',
+                     diffreplace(12, 12, '', 'b\nc\n.\n'),
+                     'd\ne\n',
+                     diffreplace(16, 18, '.\n', ''), 'f\n']
+        self.assert_(got in (want_c, want_pure),
+                     'got: %r, wanted either %r or %r' % (
+                         got, want_c, want_pure))
 
     def test_fixws(self):
         cases = [
             (" \ta\r b\t\n", "ab\n", 1),
             (" \ta\r b\t\n", " a b\n", 0),
             ("", "", 1),
             ("", "", 0),
         ]
         for a, b, allws in cases:
             c = bdiff.fixws(a, allws)
             self.assertEqual(
                 c, b, 'fixws(%r) want %r got %r (allws=%r)' % (a, b, c, allws))
 
     def test_nice_diff_for_trivial_change(self):
         self.assertEqual(self.showdiff(
             ''.join('<%s\n-\n' % i for i in range(5)),
             ''.join('>%s\n-\n' % i for i in range(5))),
                          [diffreplace(0, 3, '<0\n', '>0\n'),
                           '-\n',
                           diffreplace(5, 8, '<1\n', '>1\n'),
                           '-\n',
                           diffreplace(10, 13, '<2\n', '>2\n'),
                           '-\n',
                           diffreplace(15, 18, '<3\n', '>3\n'),
                           '-\n',
                           diffreplace(20, 23, '<4\n', '>4\n'),
                           '-\n'])
 
     def test_prefer_appending(self):
         # 1 line to 3 lines
         self.assertEqual(self.showdiff('a\n', 'a\n' * 3),
                          ['a\n', diffreplace(2, 2, '', 'a\na\n')])
         # 1 line to 5 lines
         self.assertEqual(self.showdiff('a\n', 'a\n' * 5),
                          ['a\n', diffreplace(2, 2, '', 'a\na\na\na\n')])
 
     def test_prefer_removing_trailing(self):
         # 3 lines to 1 line
         self.assertEqual(self.showdiff('a\n' * 3, 'a\n'),
                          ['a\n', diffreplace(2, 6, 'a\na\n', '')])
         # 5 lines to 1 line
         self.assertEqual(self.showdiff('a\n' * 5, 'a\n'),
                          ['a\n', diffreplace(2, 10, 'a\na\na\na\n', '')])
 
 if __name__ == '__main__':
     silenttestrunner.main(__name__)