Patch #1581073: add a flag to textwrap that prevents the dropping of

whitespace while wrapping.

2 files changed, 16 insertions, 4 deletions

diff --git a/Lib/test/test_textwrap.py b/Lib/test/test_textwrap.py
index 500eceb183..5f0b51b4e7 100644
--- a/Lib/test/test_textwrap.py
+++ b/Lib/test/test_textwrap.py
@@ -328,6 +328,14 @@ What a mess!
         self.check_wrap(text, 30,
                         [" This is a sentence with", "leading whitespace."])
 
+    def test_no_drop_whitespace(self):
+        # SF patch #1581073
+        text = " This is a    sentence with     much whitespace."
+        self.check_wrap(text, 10,
+                        [" This is a", "    ", "sentence ",
+                         "with     ", "much white", "space."],
+                        drop_whitespace=False)
+
     if test_support.have_unicode:
         def test_unicode(self):
             # *Very* simple test of wrapping Unicode strings.  I'm sure
diff --git a/Lib/textwrap.py b/Lib/textwrap.py
index ccff2aba12..e49644d221 100644
--- a/Lib/textwrap.py
+++ b/Lib/textwrap.py
@@ -63,6 +63,8 @@ class TextWrapper:
       break_long_words (default: true)
         Break words longer than 'width'.  If false, those words will not
         be broken, and some lines might be longer than 'width'.
+      drop_whitespace (default: true)
+        Drop leading and trailing whitespace from lines.
     """
 
     whitespace_trans = string.maketrans(_whitespace, ' ' * len(_whitespace))
@@ -98,7 +100,8 @@ class TextWrapper:
                  expand_tabs=True,
                  replace_whitespace=True,
                  fix_sentence_endings=False,
-                 break_long_words=True):
+                 break_long_words=True,
+                 drop_whitespace=True):
         self.width = width
         self.initial_indent = initial_indent
         self.subsequent_indent = subsequent_indent
@@ -106,6 +109,7 @@ class TextWrapper:
         self.replace_whitespace = replace_whitespace
         self.fix_sentence_endings = fix_sentence_endings
         self.break_long_words = break_long_words
+        self.drop_whitespace = drop_whitespace
 
 
     # -- Private methods -----------------------------------------------
@@ -140,7 +144,7 @@ class TextWrapper:
           'use', ' ', 'the', ' ', '-b', ' ', 'option!'
         """
         chunks = self.wordsep_re.split(text)
-        chunks = filter(None, chunks)
+        chunks = filter(None, chunks)  # remove empty chunks
         return chunks
 
     def _fix_sentence_endings(self, chunks):
@@ -228,7 +232,7 @@ class TextWrapper:
 
             # First chunk on line is whitespace -- drop it, unless this
             # is the very beginning of the text (ie. no lines started yet).
-            if chunks[-1].strip() == '' and lines:
+            if self.drop_whitespace and chunks[-1].strip() == '' and lines:
                 del chunks[-1]
 
             while chunks:
@@ -249,7 +253,7 @@ class TextWrapper:
                 self._handle_long_word(chunks, cur_line, cur_len, width)
 
             # If the last chunk on this line is all whitespace, drop it.
-            if cur_line and cur_line[-1].strip() == '':
+            if self.drop_whitespace and cur_line and cur_line[-1].strip() == '':
                 del cur_line[-1]
 
             # Convert current line back to a string and store it in list