[pyupgrade] Show violations without auto-fix for UP031 (#11229)

Co-authored-by: Micha Reiser <micha@reiser.io>

Author: autinerd

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

@@ -139,3 +139,33 @@
 
 print("%2X" % 1)
 print("%02X" % 1)
+
+# UP031 (no longer false negatives, but offer no fix because of more complex syntax)
+
+"%d.%d" % (a, b)
+
+"%*s" % (5, "hi")
+
+"%d" % (flt,)
+
+"%c" % (some_string,)
+
+"%.2r" % (1.25)
+
+"%.*s" % (5, "hi")
+
+"%i" % (flt,)
+
+"%()s" % {"": "empty"}
+
+"%s" % {"k": "v"}
+
+"%()s" % {"": "bar"}
+
+"%(1)s" % {"1": "bar"}
+
+"%(a)s" % {"a": 1, "a": 2}
+
+"%(1)s" % {1: 2, "1": 2}
+
+"%(and)s" % {"and": 2}

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP031_1.py

@@ -1,34 +1,8 @@
 # OK
 b"%s" % (b"bytestring",)
 
-"%*s" % (5, "hi")
-
-"%d" % (flt,)
-
-"%c" % (some_string,)
-
 "%4%" % ()
 
-"%.2r" % (1.25)
-
 i % 3
 
-"%.*s" % (5, "hi")
-
-"%i" % (flt,)
-
-"%()s" % {"": "empty"}
-
-"%s" % {"k": "v"}
-
-"%(1)s" % {"1": "bar"}
-
-"%(a)s" % {"a": 1, "a": 2}
-
 pytest.param('"%8s" % (None,)', id="unsafe width-string conversion"),
-
-"%()s" % {"": "bar"}
-
-"%(1)s" % {1: 2, "1": 2}
-
-"%(and)s" % {"and": 2}

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

@@ -14,7 +14,7 @@ mod tests {
 
     use crate::registry::Rule;
     use crate::rules::pyupgrade;
-    use crate::settings::types::PythonVersion;
+    use crate::settings::types::{PreviewMode, PythonVersion};
     use crate::test::test_path;
     use crate::{assert_messages, settings};
 
@@ -100,6 +100,19 @@ mod tests {
         Ok(())
     }
 
+    #[test_case(Rule::PrintfStringFormatting, Path::new("UP031_0.py"))]
+    fn preview(rule_code: Rule, path: &Path) -> Result<()> {
+        let diagnostics = test_path(
+            Path::new("pyupgrade").join(path),
+            &settings::LinterSettings {
+                preview: PreviewMode::Enabled,
+                ..settings::LinterSettings::for_rule(rule_code)
+            },
+        )?;
+        assert_messages!(diagnostics);
+        Ok(())
+    }
+
     #[test]
     fn async_timeout_error_alias_not_applied_py310() -> Result<()> {
         let diagnostics = test_path(

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

@@ -28,21 +28,29 @@ use crate::rules::pyupgrade::helpers::curly_escape;
 /// formatting.
 ///
 /// ## Example
+///
 /// ```python
 /// "%s, %s" % ("Hello", "World")  # "Hello, World"
 /// ```
 ///
 /// Use instead:
+///
 /// ```python
 /// "{}, {}".format("Hello", "World")  # "Hello, World"
 /// ```
 ///
+/// ```python
+/// f"{'Hello'}, {'World'}"  # "Hello, World"
+/// ```
+///
 /// ## Fix safety
+///
 /// In cases where the format string contains a single generic format specifier
 /// (e.g. `%s`), and the right-hand side is an ambiguous expression,
 /// we cannot offer a safe fix.
 ///
 /// For example, given:
+///
 /// ```python
 /// "%s" % val
 /// ```
@@ -379,6 +387,11 @@ pub(crate) fn printf_string_formatting(
             return;
         };
         if !convertible(&format_string, right) {
+            if checker.settings.preview.is_enabled() {
+                checker
+                    .diagnostics
+                    .push(Diagnostic::new(PrintfStringFormatting, string_expr.range()));
+            }
             return;
         }
 
@@ -437,6 +450,11 @@ pub(crate) fn printf_string_formatting(
             let Some(params_string) =
                 clean_params_dictionary(right, checker.locator(), checker.stylist())
             else {
+                if checker.settings.preview.is_enabled() {
+                    checker
+                        .diagnostics
+                        .push(Diagnostic::new(PrintfStringFormatting, string_expr.range()));
+                }
                 return;
             };
             Cow::Owned(params_string)

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

@@ -1142,12 +1142,16 @@ UP031_0.py:140:7: UP031 [*] Use format specifiers instead of percent format
 140     |-print("%2X" % 1)
     140 |+print("{:2X}".format(1))
 141 141 | print("%02X" % 1)
+142 142 | 
+143 143 | # UP031 (no longer false negatives, but offer no fix because of more complex syntax)
 
 UP031_0.py:141:7: UP031 [*] Use format specifiers instead of percent format
     |
 140 | print("%2X" % 1)
 141 | print("%02X" % 1)
     |       ^^^^^^^^^^ UP031
+142 | 
+143 | # UP031 (no longer false negatives, but offer no fix because of more complex syntax)
     |
     = help: Replace with format specifiers
 
@@ -1157,3 +1161,6 @@ UP031_0.py:141:7: UP031 [*] Use format specifiers instead of percent format
 140 140 | print("%2X" % 1)
 141     |-print("%02X" % 1)
     141 |+print("{:02X}".format(1))
+142 142 | 
+143 143 | # UP031 (no longer false negatives, but offer no fix because of more complex syntax)
+144 144 |