Issue #21827: Fixed textwrap.dedent() for the case when largest common
whitespace is a substring of smallest leading whitespace.
Based on patch by Robert Li.
diff --git a/Lib/test/test_textwrap.py b/Lib/test/test_textwrap.py
index 707aaaa..a44184f 100644
--- a/Lib/test/test_textwrap.py
+++ b/Lib/test/test_textwrap.py
@@ -748,6 +748,11 @@
expect = "hello there\n how are you?"
self.assertEqual(expect, dedent(text))
+ # test margin is smaller than smallest indent
+ text = " \thello there\n \thow are you?\n \tI'm fine, thanks"
+ expect = " \thello there\n \thow are you?\n\tI'm fine, thanks"
+ self.assertEqual(expect, dedent(text))
+
# Test textwrap.indent
class IndentTestCase(unittest.TestCase):
diff --git a/Lib/textwrap.py b/Lib/textwrap.py
index 3ad3e18..05e0306 100644
--- a/Lib/textwrap.py
+++ b/Lib/textwrap.py
@@ -444,11 +444,15 @@
elif margin.startswith(indent):
margin = indent
- # Current line and previous winner have no common whitespace:
- # there is no margin.
+ # Find the largest common whitespace between current line and previous
+ # winner.
else:
- margin = ""
- break
+ for i, (x, y) in enumerate(zip(margin, indent)):
+ if x != y:
+ margin = margin[:i]
+ break
+ else:
+ margin = margin[:len(indent)]
# sanity check (testing/debugging only)
if 0 and margin:
diff --git a/Misc/ACKS b/Misc/ACKS
index b6089fd..f8fcccf 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -847,6 +847,7 @@
Ivan Levkivskyi
William Lewis
Akira Li
+Robert Li
Xuanji Li
Robert van Liere
Ross Light
diff --git a/Misc/NEWS b/Misc/NEWS
index 7e7534d..638964e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -45,6 +45,10 @@
Library
-------
+- Issue #21827: Fixed textwrap.dedent() for the case when largest common
+ whitespace is a substring of smallest leading whitespace.
+ Based on patch by Robert Li.
+
- Issue #25447: The lru_cache() wrapper objects now can be copied and pickled
(by returning the original object unchanged).