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.

1 files changed, 5 insertions, 0 deletions

diff --git a/Lib/test/test_textwrap.py b/Lib/test/test_textwrap.py
index 1bba77eb9e..ea7c0895c1 100644
--- a/Lib/test/test_textwrap.py
+++ b/Lib/test/test_textwrap.py
@@ -732,6 +732,11 @@ def foo():
         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):