Revert rest of f4cef9c

skirpichev · skirpichev · commit 6baf2eeb3e6c · 2025-04-07T10:51:11.000+03:00
Python docs doesn't specify 0-padding behavior, when alignment is
specified.  Lets be more strict here as Fraction/Decimal's: just reject
0 flag in this case.

float's behavior is just odd:
&gt;&gt;&gt; format(1.123, '&lt;020f')
'1.123000000000000000'
diff --git a/mpmath/libmp/libmpf.py b/mpmath/libmp/libmpf.py
@@ -1474,17 +1474,22 @@ def read_format_spec(format_spec):
             format_dict['rounding'] = _GMPY_ROUND_CHAR_DICT[rounding_char]
 
         if match['zeropad']:
-            if not match['align']:
-                format_dict['align'] = '='
-            if not match['fill_char']:
-                format_dict['fill_char'] = '0'
-
-        if format_dict['precision'] < 0 and format_dict['type'].lower() not in ['', 'a', 'b']:
+            if match['fill_char']:
+                raise ValueError("Fill character conflicts with '0'"
+                                 f" in format specifier: '{format_spec}'")
+            if match['align']:
+                raise ValueError("Alignment conflicts with '0'"
+                                 f" in format specifier: '{format_spec}'")
+            format_dict['align'] = '='
+            format_dict['fill_char'] = '0'
+
+        if format_dict['precision'] < 0 and (format_dict['type'].lower()
+                                             not in ['', 'a', 'b']):
             format_dict['precision'] = 6
-    else:
-        raise ValueError("Invalid format specifier '{}'".format(format_spec))
 
-    return format_dict
+        return format_dict
+
+    raise ValueError(f"Invalid format specifier '{format_spec}'")
 
 
 def format_fixed(s, precision=6, rounding=round_nearest):
diff --git a/mpmath/tests/test_format.py b/mpmath/tests/test_format.py
@@ -618,8 +618,8 @@ def test_mpf_fmt():
 
         # Tests for = alignment
         assert f"{mp.mpf('0.24'):=+20.2f}" == '+               0.24'
-        assert f"{mp.mpf('0.24'):=+020.2e}" == '+000000000002.40e-01'
-        assert f"{mp.mpf('0.24'):=+020.2g}" == '+0000000000000000.24'
+        assert f"{mp.mpf('0.24'):0=+20.2e}" == '+000000000002.40e-01'
+        assert f"{mp.mpf('0.24'):0=+20.2g}" == '+0000000000000000.24'
 
         # Tests for different kinds of rounding
         num = mp.mpf('-1.23456789999901234567')
@@ -816,6 +816,13 @@ def test_errors():
     with pytest.raises(ValueError, match="Invalid format specifier '12.3 E '"):
         f"{mp.mpf('4'):12.3 E }"
 
+    with pytest.raises(ValueError, match="Fill character conflicts"):
+        f"{mp.mpf('4'):q<03f}"
+    with pytest.raises(ValueError, match="Alignment conflicts"):
+        f"{mp.mpf('4'):=03f}"
+    with pytest.raises(ValueError, match="Fill character conflicts"):
+        f"{mp.mpf('4'): =03f}"
+
 
 @settings(max_examples=10000)
 @given(st.floats(allow_nan=True, allow_infinity=True,
