[flake8-implicit-str-concat] Avoid invalid fix generated by autofix (ISC003)

As reported in #19757:
While attempting ISC003 autofix for an expression with explicit string
concatenation, with either operand being a string literal that wraps
across multiple lines (in parentheses) - it resulted in generating
a fix which caused runtime error.

Example:
_ = "abc" + (
    "def"
    "ghi"
)
was being auto-fixed to:
_ = "abc" (
    "def"
    "ghi"
)
which raised `TypeError: 'str' object is not callable`

This commit makes changes to just report diagnostic - no autofix
in such cases.

Fixes #19757.

Signed-off-by: Prakhar Pratyush <[email protected]>

Author: prakhar1144

crates/ruff_linter/resources/test/fixtures/flake8_implicit_str_concat/ISC.py

@@ -208,3 +208,17 @@
 _ = f"b {t"abc" \
     t"def"} g"
 
+
+# Explicit concatenation with either operand being
+# a string literal that wraps across multiple lines (in parentheses)
+# reports diagnostic - no autofix.
+# See https://github.com/astral-sh/ruff/issues/19757
+_ = "abc" + (
+    "def"
+    "ghi"
+)
+
+_ = (
+    "abc"
+    "def"
+) + "ghi"

crates/ruff_linter/src/rules/flake8_implicit_str_concat/rules/explicit.rs

@@ -1,12 +1,12 @@
 use ruff_macros::{ViolationMetadata, derive_message_formats};
+use ruff_python_ast::parenthesize::parenthesized_range;
 use ruff_python_ast::{self as ast, Expr, Operator};
 use ruff_python_trivia::is_python_whitespace;
 use ruff_source_file::LineRanges;
 use ruff_text_size::{Ranged, TextLen, TextRange, TextSize};
 
-use crate::AlwaysFixableViolation;
 use crate::checkers::ast::Checker;
-use crate::{Edit, Fix};
+use crate::{Edit, Fix, FixAvailability, Violation};
 
 /// ## What it does
 /// Checks for string literals that are explicitly concatenated (using the
@@ -36,14 +36,16 @@ use crate::{Edit, Fix};
 #[violation_metadata(stable_since = "v0.0.201")]
 pub(crate) struct ExplicitStringConcatenation;
 
-impl AlwaysFixableViolation for ExplicitStringConcatenation {
+impl Violation for ExplicitStringConcatenation {
+    const FIX_AVAILABILITY: FixAvailability = FixAvailability::Sometimes;
+
     #[derive_message_formats]
     fn message(&self) -> String {
         "Explicitly concatenated string should be implicitly concatenated".to_string()
     }
 
-    fn fix_title(&self) -> String {
-        "Remove redundant '+' operator to implicitly concatenate".to_string()
+    fn fix_title(&self) -> Option<String> {
+        Some("Remove redundant '+' operator to implicitly concatenate".to_string())
     }
 }
 
@@ -82,9 +84,25 @@ pub(crate) fn explicit(checker: &Checker, expr: &Expr) {
                     .locator()
                     .contains_line_break(TextRange::new(left.end(), right.start()))
             {
-                checker
-                    .report_diagnostic(ExplicitStringConcatenation, expr.range())
-                    .set_fix(generate_fix(checker, bin_op));
+                let mut diagnostic =
+                    checker.report_diagnostic(ExplicitStringConcatenation, expr.range());
+
+                let is_parenthesized = |expr: &Expr| {
+                    parenthesized_range(
+                        expr.into(),
+                        bin_op.into(),
+                        checker.comment_ranges(),
+                        checker.source(),
+                    )
+                    .is_some()
+                };
+                // If either `left` or `right` is parenthesized, generating
+                // a fix would be too involved. Just report the diagnostic.
+                if is_parenthesized(left) || is_parenthesized(right) {
+                    return;
+                }
+
+                diagnostic.set_fix(generate_fix(checker, bin_op));
             }
         }
     }

crates/ruff_linter/src/rules/flake8_implicit_str_concat/snapshots/ruff_linter__rules__flake8_implicit_str_concat__tests__ISC003_ISC.py.snap

@@ -357,3 +357,33 @@ help: Remove redundant '+' operator to implicitly concatenate
 203 | )
 204 | 
 205 | # nested examples with both t and f-strings
+
+ISC003 Explicitly concatenated string should be implicitly concatenated
+   --> ISC.py:216:5
+    |
+214 |   # reports diagnostic - no autofix.
+215 |   # See https://github.com/astral-sh/ruff/issues/19757
+216 |   _ = "abc" + (
+    |  _____^
+217 | |     "def"
+218 | |     "ghi"
+219 | | )
+    | |_^
+220 |
+221 |   _ = (
+    |
+help: Remove redundant '+' operator to implicitly concatenate
+
+ISC003 Explicitly concatenated string should be implicitly concatenated
+   --> ISC.py:221:5
+    |
+219 |   )
+220 |
+221 |   _ = (
+    |  _____^
+222 | |     "abc"
+223 | |     "def"
+224 | | ) + "ghi"
+    | |_________^
+    |
+help: Remove redundant '+' operator to implicitly concatenate

crates/ruff_linter/src/rules/flake8_implicit_str_concat/snapshots/ruff_linter__rules__flake8_implicit_str_concat__tests__multiline_ISC002_ISC.py.snap

@@ -89,3 +89,24 @@ ISC002 Implicitly concatenated string literals over multiple lines
 209 | |     t"def"} g"
     | |__________^
     |
+
+ISC002 Implicitly concatenated string literals over multiple lines
+   --> ISC.py:217:5
+    |
+215 |   # See https://github.com/astral-sh/ruff/issues/19757
+216 |   _ = "abc" + (
+217 | /     "def"
+218 | |     "ghi"
+    | |_________^
+219 |   )
+    |
+
+ISC002 Implicitly concatenated string literals over multiple lines
+   --> ISC.py:222:5
+    |
+221 |   _ = (
+222 | /     "abc"
+223 | |     "def"
+    | |_________^
+224 |   ) + "ghi"
+    |