Tighten up the regex - extra leading zeros not permitted

mdickinson · mdickinson · commit 67e020cc4ea2 · 2022-12-21T10:49:08.000Z
diff --git a/Lib/fractions.py b/Lib/fractions.py
@@ -149,10 +149,12 @@ def _round_to_figures(n, d, figures):
     (?P<sign>[-+ ]?)
     (?P<no_neg_zero>z)?
     (?P<alt>\#)?
-    (?P<zeropad>0(?=\d))?   # lookahead so that an isolated '0' is treated
-    (?P<minimumwidth>\d+)?  # as a minimum width rather than a zeropad flag
+    # lookahead so that a single '0' is treated as a minimum width rather
+    # than a zeropad flag
+    (?P<zeropad>0(?=[0-9]))?
+    (?P<minimumwidth>0|[1-9][0-9]*)?
     (?P<thousands_sep>[,_])?
-    (?:\.(?P<precision>\d+))?
+    (?:\.(?P<precision>0|[1-9][0-9]*))?
     (?P<presentation_type>[efg%])
 """, re.DOTALL | re.IGNORECASE | re.VERBOSE).fullmatch
 
diff --git a/Lib/test/test_fractions.py b/Lib/test/test_fractions.py
@@ -965,9 +965,6 @@ def test_format_f_presentation_type(self):
             (F('0.001'), '-z.2f', '0.00'),
             (F('0.001'), '+z.2f', '+0.00'),
             (F('0.001'), ' z.2f', ' 0.00'),
-            # Corner-case: leading zeros are allowed in the precision
-            (F(2, 3), '.02f', '0.67'),
-            (F(22, 7), '.000f', '3'),
             # Specifying a minimum width
             (F(2, 3), '6.2f', '  0.67'),
             (F(12345), '6.2f', '12345.00'),
@@ -1185,6 +1182,12 @@ def test_invalid_formats(self):
             "=010%",
             '>00.2f',
             '>00f',
+            # Too many zeros - minimum width should not have leading zeros
+            '006f',
+            # Leading zeros in precision
+            '.010f',
+            '.02f',
+            '.000f',
             # Missing precision
             ".e",
             ".f",
