Merge pull request #529 from asottile/percent-format-no-string-widths

don't rewrite %-format with width+s
asottile · Sep 10, 2021 · e43a16c · e43a16c
2 parents 6b2d0d8 + 7931123
commit e43a16c
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Showing 2 changed files with 6 additions and 4 deletions.
diff --git a/pyupgrade/_plugins/percent_format.py b/pyupgrade/_plugins/percent_format.py
@@ -128,8 +128,6 @@ def _handle_part(part: PercentFormat) -> str:
             if conversion == '%':
                 return s + '%'
             parts = [s, '{']
-            if width and conversion == 's' and not conversion_flag:
-                conversion_flag = '>'
             if conversion == 's':
                 conversion = ''
             if key:
@@ -276,6 +274,9 @@ def visit_BinOp(
                 # no equivalent in format
                 if conversion in {'a', 'r'} and nontrivial_fmt:
                     break
+                # %s with None and width is not supported
+                if width and conversion == 's':
+                    break
                 # all dict substitutions must be named
                 if isinstance(node.right, ast.Dict) and not key:
                     break

diff --git a/tests/features/percent_format_test.py b/tests/features/percent_format_test.py
@@ -158,6 +158,7 @@ def test_simplify_conversion_flag(s, expected):
         '"%4%" % ()',
         # no equivalent in format specifier
         '"%.2r" % (1.25)', '"%.2a" % (1.25)',
+        pytest.param('"%8s" % (None,)', id='unsafe width-string conversion'),
         # non-string mod
         'i % 3',
         # dict format but not keyed arguments
@@ -208,8 +209,8 @@ def test_percent_format_noop_if_bug_16806():
         ('"%s" % ("%s" % ("nested",),)', '"{}".format("{}".format("nested"))'),
         ('"%s%% percent" % (15,)', '"{}% percent".format(15)'),
         ('"%3f" % (15,)', '"{:3f}".format(15)'),
-        ('"%-5s" % ("hi",)', '"{:<5}".format("hi")'),
-        ('"%9s" % (5,)', '"{:>9}".format(5)'),
+        ('"%-5f" % (5,)', '"{:<5f}".format(5)'),
+        ('"%9f" % (5,)', '"{:9f}".format(5)'),
         ('"brace {} %s" % (1,)', '"brace {{}} {}".format(1)'),
         (
             '"%s" % (\n'