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/textwrap.py b/Lib/textwrap.py
index 58867f9..1759b0d 100644
--- a/Lib/textwrap.py
+++ b/Lib/textwrap.py
@@ -429,11 +429,15 @@
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: