tests/test-bdiff.py

bdiff: give slight preference to removing trailing lines

[This change could be folded into the previous changeset to minimize the repo
churn ...]

Similar to the previous change, introduce an exception to the general
preference for matches in the middle of bdiff ranges: If the best match on the
B side starts at the beginning of the bdiff range, don't aim for the
middle-most A side match but for the earliest.

New (later) matches on the A side will only be considered better if the
corresponding match on the B side *not* is at the beginning of the range.
Thus, if the best (middle-most) match on the B side turns out to be at the
beginning of the range, the earliest match on the A side will be used.

The bundle size for 4.0 (hg bundle --base null -r 4.0 x.hg) happens to go from
22807275 to 22808120 bytes - a 0.004% increase.

from __future__ import absolute_import, print_function
import struct
from mercurial import (
    bdiff,
    mpatch,
)

def test1(a, b):
    d = bdiff.bdiff(a, b)
    c = a
    if d:
        c = mpatch.patches(a, [d])
    if c != b:
        print("bad diff+patch result from\n  %r to\n  %r:" % (a, b))
        print("bdiff: %r" % d)
        print("patched: %r" % c[:200])

def test(a, b):
    print("test", repr(a), repr(b))
    test1(a, b)
    test1(b, a)

test("a\nc\n\n\n\n", "a\nb\n\n\n")
test("a\nb\nc\n", "a\nc\n")
test("", "")
test("a\nb\nc", "a\nb\nc")
test("a\nb\nc\nd\n", "a\nd\n")
test("a\nb\nc\nd\n", "a\nc\ne\n")
test("a\nb\nc\n", "a\nc\n")
test("a\n", "c\na\nb\n")
test("a\n", "")
test("a\n", "b\nc\n")
test("a\n", "c\na\n")
test("", "adjfkjdjksdhfksj")
test("", "ab")
test("", "abc")
test("a", "a")
test("ab", "ab")
test("abc", "abc")
test("a\n", "a\n")
test("a\nb", "a\nb")

#issue1295
def showdiff(a, b):
    print('showdiff(\n  %r,\n  %r):' % (a, b))
    bin = bdiff.bdiff(a, b)
    pos = 0
    q = 0
    while pos < len(bin):
        p1, p2, l = struct.unpack(">lll", bin[pos:pos + 12])
        pos += 12
        if p1:
            print('', repr(a[q:p1]))
        print('', p1, p2, repr(a[p1:p2]), '->', repr(bin[pos:pos + l]))
        pos += l
        q = p2
    if q < len(a):
        print('', repr(a[q:]))

showdiff("x\n\nx\n\nx\n\nx\n\nz\n", "x\n\nx\n\ny\n\nx\n\nx\n\nz\n")
showdiff("x\n\nx\n\nx\n\nx\n\nz\n", "x\n\nx\n\ny\n\nx\n\ny\n\nx\n\nz\n")
# we should pick up abbbc. rather than bc.de as the longest match
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")

print("done")

def testfixws(a, b, allws):
    c = bdiff.fixws(a, allws)
    if c != b:
        print("*** fixws", repr(a), repr(b), allws)
        print("got:")
        print(repr(c))

testfixws(" \ta\r b\t\n", "ab\n", 1)
testfixws(" \ta\r b\t\n", " a b\n", 0)
testfixws("", "", 1)
testfixws("", "", 0)

print("done")

print("Nice diff for a trivial change:")
showdiff(
    ''.join('<%s\n-\n' % i for i in range(5)),
    ''.join('>%s\n-\n' % i for i in range(5)))

print("Diff 1 to 3 lines - preference for appending:")
showdiff('a\n', 'a\n' * 3)
print("Diff 1 to 5 lines - preference for appending:")
showdiff('a\n', 'a\n' * 5)
print("Diff 3 to 1 lines - preference for removing trailing lines:")
showdiff('a\n' * 3, 'a\n')
print("Diff 5 to 1 lines - preference for removing trailing lines:")
showdiff('a\n' * 5, 'a\n')