Use colon rather than dot formatting for integer-only types

Author: charliermarsh

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP031_0.py

@@ -129,3 +129,10 @@
 # Not a valid type annotation but this test shouldn't result in a panic.
 # Refer: https://github.com/astral-sh/ruff/issues/11736
 x: "'%s + %s' % (1, 2)"
+
+# See: https://github.com/astral-sh/ruff/issues/12421
+print("%.2X" % 1)
+print("%.02X" % 1)
+print("%02X" % 1)
+print("%.00002X" % 1)
+print("%.20X" % 1)

crates/ruff_linter/src/rules/pyupgrade/rules/printf_string_formatting.rs

@@ -150,8 +150,19 @@ fn handle_part(part: &CFormatPart<String>) -> Cow<'_, str> {
                     match precision {
                         CFormatPrecision::Quantity(quantity) => match quantity {
                             CFormatQuantity::Amount(amount) => {
-                                format_string.push('.');
-                                format_string.push_str(&amount.to_string());
+                                // Integer-only presentation types.
+                                //
+                                // See: https://docs.python.org/3/library/string.html#format-specification-mini-language
+                                if matches!(
+                                    spec.format_char,
+                                    'b' | 'c' | 'd' | 'o' | 'x' | 'X' | 'n'
+                                ) {
+                                    format_string.push('0');
+                                    format_string.push_str(&amount.to_string());
+                                } else {
+                                    format_string.push('.');
+                                    format_string.push_str(&amount.to_string());
+                                }
                             }
                             CFormatQuantity::FromValuesTuple => {
                                 unreachable!("Width should be a usize")

crates/ruff_linter/src/rules/pyupgrade/snapshots/ruff_linter__rules__pyupgrade__tests__UP031_0.py.snap

@@ -1007,6 +1007,8 @@ UP031_0.py:131:5: UP031 [*] Use format specifiers instead of percent format
 130 | # Refer: https://github.com/astral-sh/ruff/issues/11736
 131 | x: "'%s + %s' % (1, 2)"
     |     ^^^^^^^^^^^^^^^^^^ UP031
+132 | 
+133 | # See: https://github.com/astral-sh/ruff/issues/12421
     |
     = help: Replace with format specifiers
 
@@ -1016,3 +1018,101 @@ UP031_0.py:131:5: UP031 [*] Use format specifiers instead of percent format
 130 130 | # Refer: https://github.com/astral-sh/ruff/issues/11736
 131     |-x: "'%s + %s' % (1, 2)"
     131 |+x: "'{} + {}'.format(1, 2)"
+132 132 | 
+133 133 | # See: https://github.com/astral-sh/ruff/issues/12421
+134 134 | print("%.2X" % 1)
+
+UP031_0.py:134:7: UP031 [*] Use format specifiers instead of percent format
+    |
+133 | # See: https://github.com/astral-sh/ruff/issues/12421
+134 | print("%.2X" % 1)
+    |       ^^^^^^^^^^ UP031
+135 | print("%.02X" % 1)
+136 | print("%02X" % 1)
+    |
+    = help: Replace with format specifiers
+
+ℹ Unsafe fix
+131 131 | x: "'%s + %s' % (1, 2)"
+132 132 | 
+133 133 | # See: https://github.com/astral-sh/ruff/issues/12421
+134     |-print("%.2X" % 1)
+    134 |+print("{:02X}".format(1))
+135 135 | print("%.02X" % 1)
+136 136 | print("%02X" % 1)
+137 137 | print("%.00002X" % 1)
+
+UP031_0.py:135:7: UP031 [*] Use format specifiers instead of percent format
+    |
+133 | # See: https://github.com/astral-sh/ruff/issues/12421
+134 | print("%.2X" % 1)
+135 | print("%.02X" % 1)
+    |       ^^^^^^^^^^^ UP031
+136 | print("%02X" % 1)
+137 | print("%.00002X" % 1)
+    |
+    = help: Replace with format specifiers
+
+ℹ Unsafe fix
+132 132 | 
+133 133 | # See: https://github.com/astral-sh/ruff/issues/12421
+134 134 | print("%.2X" % 1)
+135     |-print("%.02X" % 1)
+    135 |+print("{:02X}".format(1))
+136 136 | print("%02X" % 1)
+137 137 | print("%.00002X" % 1)
+138 138 | print("%.20X" % 1)
+
+UP031_0.py:136:7: UP031 [*] Use format specifiers instead of percent format
+    |
+134 | print("%.2X" % 1)
+135 | print("%.02X" % 1)
+136 | print("%02X" % 1)
+    |       ^^^^^^^^^^ UP031
+137 | print("%.00002X" % 1)
+138 | print("%.20X" % 1)
+    |
+    = help: Replace with format specifiers
+
+ℹ Unsafe fix
+133 133 | # See: https://github.com/astral-sh/ruff/issues/12421
+134 134 | print("%.2X" % 1)
+135 135 | print("%.02X" % 1)
+136     |-print("%02X" % 1)
+    136 |+print("{:02X}".format(1))
+137 137 | print("%.00002X" % 1)
+138 138 | print("%.20X" % 1)
+
+UP031_0.py:137:7: UP031 [*] Use format specifiers instead of percent format
+    |
+135 | print("%.02X" % 1)
+136 | print("%02X" % 1)
+137 | print("%.00002X" % 1)
+    |       ^^^^^^^^^^^^^^ UP031
+138 | print("%.20X" % 1)
+    |
+    = help: Replace with format specifiers
+
+ℹ Unsafe fix
+134 134 | print("%.2X" % 1)
+135 135 | print("%.02X" % 1)
+136 136 | print("%02X" % 1)
+137     |-print("%.00002X" % 1)
+    137 |+print("{:02X}".format(1))
+138 138 | print("%.20X" % 1)
+
+UP031_0.py:138:7: UP031 [*] Use format specifiers instead of percent format
+    |
+136 | print("%02X" % 1)
+137 | print("%.00002X" % 1)
+138 | print("%.20X" % 1)
+    |       ^^^^^^^^^^^ UP031
+    |
+    = help: Replace with format specifiers
+
+ℹ Unsafe fix
+135 135 | print("%.02X" % 1)
+136 136 | print("%02X" % 1)
+137 137 | print("%.00002X" % 1)
+138     |-print("%.20X" % 1)
+    138 |+print("{:020X}".format(1))