[pylint] Improve handling of concatenated strings (PLE1300)

crates/ruff_linter/resources/test/fixtures/pylint/bad_string_format_character.py

@@ -29,7 +29,7 @@
 
 f"{1:z}"  # [bad-format-character]
 
-## False negatives
+## Supporting concatenated strings
 
 print(("%" "z") % 1)
 

crates/ruff_linter/src/checkers/ast/analyze/expression.rs

@@ -1469,6 +1469,7 @@ pub(crate) fn expression(expr: &Expr, checker: &Checker) {
                     Rule::PercentFormatPositionalCountMismatch,
                     Rule::PercentFormatStarRequiresSequence,
                     Rule::PercentFormatUnsupportedFormatCharacter,
+                    Rule::BadStringFormatCharacter,
                 ]) {
                     let location = expr.range();
                     match pyflakes::cformat::CFormatSummary::try_from(value.to_str()) {
@@ -1483,6 +1484,11 @@ pub(crate) fn expression(expr: &Expr, checker: &Checker) {
                                 },
                                 location,
                             );
+                            // PLE1300
+                            checker.report_diagnostic_if_enabled(
+                                pylint::rules::BadStringFormatCharacter { format_char: c },
+                                location,
+                            );
                         }
                         Err(e) => {
                             // F501
@@ -1535,13 +1541,6 @@ pub(crate) fn expression(expr: &Expr, checker: &Checker) {
                 if checker.is_rule_enabled(Rule::PrintfStringFormatting) {
                     pyupgrade::rules::printf_string_formatting(checker, bin_op, format_string);
                 }
-                if checker.is_rule_enabled(Rule::BadStringFormatCharacter) {
-                    pylint::rules::bad_string_format_character::percent(
-                        checker,
-                        expr,
-                        format_string,
-                    );
-                }
                 if checker.is_rule_enabled(Rule::BadStringFormatType) {
                     pylint::rules::bad_string_format_type(checker, bin_op, format_string);
                 }

crates/ruff_linter/src/rules/pylint/rules/bad_string_format_character.rs

@@ -1,14 +1,10 @@
-use std::str::FromStr;
-
 use ruff_macros::{ViolationMetadata, derive_message_formats};
-use ruff_python_ast::{Expr, ExprStringLiteral, StringFlags, StringLiteral};
 use ruff_python_literal::{
-    cformat::{CFormatErrorType, CFormatString},
     format::FormatPart,
     format::FromTemplate,
     format::{FormatSpec, FormatSpecError, FormatString},
 };
-use ruff_text_size::{Ranged, TextRange};
+use ruff_text_size::TextRange;
 
 use crate::Violation;
 use crate::checkers::ast::Checker;
@@ -29,7 +25,7 @@ use crate::checkers::ast::Checker;
 #[derive(ViolationMetadata)]
 #[violation_metadata(stable_since = "v0.0.283")]
 pub(crate) struct BadStringFormatCharacter {
-    format_char: char,
+    pub(crate) format_char: char,
 }
 
 impl Violation for BadStringFormatCharacter {
@@ -72,26 +68,3 @@ pub(crate) fn call(checker: &Checker, string: &str, range: TextRange) {
         }
     }
 }
-
-/// PLE1300
-/// Ex) `"%z" % "1"`
-pub(crate) fn percent(checker: &Checker, expr: &Expr, format_string: &ExprStringLiteral) {
-    for StringLiteral {
-        value: _,
-        node_index: _,
-        range,
-        flags,
-    } in &format_string.value
-    {
-        let string = checker.locator().slice(range);
-        let string = &string
-            [usize::from(flags.opener_len())..(string.len() - usize::from(flags.closer_len()))];
-
-        // Parse the format string (e.g. `"%s"`) into a list of `PercentFormat`.
-        if let Err(format_error) = CFormatString::from_str(string) {
-            if let CFormatErrorType::UnsupportedFormatChar(format_char) = format_error.typ {
-                checker.report_diagnostic(BadStringFormatCharacter { format_char }, expr.range());
-            }
-        }
-    }
-}

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLE1300_bad_string_format_character.py.snap

@@ -67,6 +67,17 @@ PLE1300 Unsupported format character 'y'
 21 | "{0:.{foo}{bar}{foobar}y}".format(...)  # OK (cannot validate after nested placeholders)
    |
 
+PLE1300 Unsupported format character 'z'
+  --> bad_string_format_character.py:34:7
+   |
+32 | ## Supporting concatenated strings
+33 |
+34 | print(("%" "z") % 1)
+   |       ^^^^^^^^^^^^^
+35 |
+36 | ## `%b` is only valid for bytes formatting.
+   |
+
 PLE1300 Unsupported format character 'b'
   --> bad_string_format_character.py:37:1
    |