differ argument instead of 2 matchers where appropriate + differ tests

Author: dg-pb

Lib/difflib.py

@@ -1490,8 +1490,7 @@ def decode(s):
     for line in lines:
         yield line.encode('ascii', 'surrogateescape')
 
-def ndiff(a, b, linejunk=None, charjunk=IS_CHARACTER_JUNK,
-          linematcher=None, charmatcher=None):
+def ndiff(a, b, linejunk=None, charjunk=IS_CHARACTER_JUNK, differ=None):
     r"""
     Compare `a` and `b` (lists of strings); return a `Differ`-style delta.
 
@@ -1509,13 +1508,9 @@ def ndiff(a, b, linejunk=None, charjunk=IS_CHARACTER_JUNK,
       whitespace characters (a blank or tab; note: it's a bad idea to
       include newline in this!).
 
-    - `linematcher`: callable that takes 3 positional arguments.
-      i.e. matcher(isjunk, a, b) which returns SequenceMatcherBase instance
-      Default (if None) is SequenceMatcher class.
-
-    - `charmatcher`: callable that takes 3 positional arguments.
-      i.e. matcher(isjunk, a, b) which returns SequenceMatcherBase instance
-      Default (if None) is SequenceMatcher class.
+    - `differ`: callable that takes 2 positional arguments.
+      i.e. differ(linejunk, charjunk) which returns `Differ` instance
+      Default (if None) is Differ class.
 
     Tools/scripts/ndiff.py is a command-line front-end to this function.
 
@@ -1534,11 +1529,15 @@ def ndiff(a, b, linejunk=None, charjunk=IS_CHARACTER_JUNK,
     + tree
     + emu
     """
-    return Differ(linejunk, charjunk, linematcher, charmatcher).compare(a, b)
+    if differ is None:
+        differ = Differ
+    elif not callable(differ):
+        raise TypeError("differ must be callable: %r" % (differ,))
+
+    return differ(linejunk, charjunk).compare(a, b)
 
 def _mdiff(fromlines, tolines, context=None,
-           linejunk=None, charjunk=IS_CHARACTER_JUNK,
-           linematcher=None, charmatcher=None):
+           linejunk=None, charjunk=IS_CHARACTER_JUNK, differ=None):
     r"""Returns generator yielding marked up from/to side by side differences.
 
     Arguments:
@@ -1548,7 +1547,7 @@ def _mdiff(fromlines, tolines, context=None,
                if None, all from/to text lines will be generated.
     linejunk -- passed on to ndiff (see ndiff documentation)
     charjunk -- passed on to ndiff (see ndiff documentation)
-    linematcher -- passed on to ndiff (see ndiff documentation)
+    differ -- passed on to ndiff (see ndiff documentation)
     charmatcher -- passed on to ndiff (see ndiff documentation)
 
     This function returns an iterator which returns a tuple:
@@ -1579,8 +1578,7 @@ def _mdiff(fromlines, tolines, context=None,
     change_re = re.compile(r'(\++|\-+|\^+)')
 
     # create the difference iterator to generate the differences
-    diff_lines_iterator = ndiff(fromlines, tolines, linejunk, charjunk,
-                                linematcher, charmatcher)
+    diff_lines_iterator = ndiff(fromlines, tolines, linejunk, charjunk, differ)
 
     def _make_line(lines, format_key, side, num_lines=[0,0]):
         """Returns line of text with user's change markup and line formatting.
@@ -1925,15 +1923,14 @@ class HtmlDiff(object):
     _default_prefix = 0
 
     def __init__(self,tabsize=8, wrapcolumn=None,
-                 linejunk=None, charjunk=IS_CHARACTER_JUNK,
-                 linematcher=None, charmatcher=None):
+                 linejunk=None, charjunk=IS_CHARACTER_JUNK, differ=None):
         """HtmlDiff instance initializer
 
         Arguments:
         tabsize -- tab stop spacing, defaults to 8.
         wrapcolumn -- column number where lines are broken and wrapped,
             defaults to None where lines are not wrapped.
-        linejunk,charjunk,linematcher,charmatcher -- keyword arguments
+        linejunk,charjunk,differ -- keyword arguments
             passed into ndiff() (used by HtmlDiff() to generate the side
             by side HTML differences).  See ndiff() documentation for
             argument default values and descriptions.
@@ -1942,8 +1939,7 @@ def __init__(self,tabsize=8, wrapcolumn=None,
         self._wrapcolumn = wrapcolumn
         self._linejunk = linejunk
         self._charjunk = charjunk
-        self._linematcher = linematcher
-        self._charmatcher = charmatcher
+        self._differ = differ
 
     def make_file(self, fromlines, tolines, fromdesc='', todesc='',
                   context=False, numlines=5, *, charset='utf-8'):
@@ -2216,7 +2212,7 @@ def make_table(self,fromlines,tolines,fromdesc='',todesc='',context=False,
             context_lines = None
         diffs = _mdiff(fromlines, tolines, context_lines,
                        linejunk=self._linejunk, charjunk=self._charjunk,
-                       linematcher=self._linematcher, charmatcher=self._charmatcher)
+                       differ=self._differ)
 
         # set up iterator to wrap lines that exceed desired width
         if self._wrapcolumn:
@@ -2774,7 +2770,7 @@ class GestaltSequenceMatcher(SequenceMatcherBase):
 
     Time Complexity:
         find_longest_match : O(n)
-        get_matching_blocks : O(n) average for common diff case
+        get_matching_blocks : O(n) - O(nlogn) for average diff case
                               O(n^2) worst case.
 
         Example of worst case complexity `get_matching_blocks` case:

Lib/test/test_difflib.py

@@ -3,6 +3,7 @@
 import unittest
 import doctest
 import sys
+import functools
 
 
 class TestWithAscii(unittest.TestCase):
@@ -283,6 +284,7 @@ def test_make_file_usascii_charset_with_nonascii_input(self):
         self.assertIn('ımplıcıt', output)
 
 class TestDiffer(unittest.TestCase):
+
     def test_close_matches_aligned(self):
         # Of the 4 closely matching pairs, we want 1 to match with 3,
         # and 2 with 4, to align with a "top to bottom" mental model.
@@ -311,6 +313,46 @@ def test_one_delete(self):
         m = difflib.Differ().compare('a' + 'b' * 2, 'b' * 2)
         self.assertEqual(list(m), ['- a', '  b', '  b'])
 
+    def test_differ_with_balancing_gestalt_matcher(self):
+        gsm_cls = functools.partial(difflib.GestaltSequenceMatcher, balancing=2/3)
+        d1 = difflib.Differ()
+        d2 = difflib.Differ(linematcher=gsm_cls, charmatcher=gsm_cls)
+        a = ["a\n", "b\n", "-\n", "a\n", "b\n", "close match 1\n", "a\n", "b\n", "c\n"]
+        b = ["a\n", "b\n", "c\n", "+\n", "a\n", "b\n", "close match 2\n", "a\n", "b\n"]
+        m = list(d1.compare(a, b))
+        self.assertEqual(m,
+                         ['- a\n',
+                          '- b\n',
+                          '- -\n',
+                          '- a\n',
+                          '- b\n',
+                          '- close match 1\n',
+                          '  a\n',
+                          '  b\n',
+                          '  c\n',
+                          '+ +\n',
+                          '+ a\n',
+                          '+ b\n',
+                          '+ close match 2\n',
+                          '+ a\n',
+                          '+ b\n'])
+        m = list(d2.compare(a, b))
+        self.assertEqual(m,
+                         ['  a\n',
+                          '  b\n',
+                          '- -\n',
+                          '+ c\n',
+                          '+ +\n',
+                          '  a\n',
+                          '  b\n',
+                          '- close match 1\n',
+                          '?             ^\n',
+                          '+ close match 2\n',
+                          '?             ^\n',
+                          '  a\n',
+                          '  b\n',
+                          '- c\n'])
+
 
 class TestOutputFormat(unittest.TestCase):
     def test_tab_delimiter(self):
@@ -724,7 +766,7 @@ def foo2(a, b):
 class TestGestaltSequenceMatcher(unittest.TestCase):
     def test_cross_test_with_autojunk_false(self):
         cases = [
-            ("ABCDEFGHIJKLMNOP" * 50, "ACEGIKMOQBDFHJLNP" * 50),
+            ("ABCDEFGHIJKLMNOP" * 10, "ACEGIKMOQBDFHJLNP" * 10),
             (
                 "".join(chr(ord('a') + i % 10) * (i + 1) for i in range(30)),
                 "".join(chr(ord('a') + i % 10) * (30 - i) for i in range(30))