Autofixer for ISC001 (#4853)

## Summary

This PR adds autofixer for rule ISC001 in cases where both string
literals are of the same kind and with same quotes (double / single).

Fixes #4829

## Test Plan

I added testcases with different combinations of string literals.

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

@@ -34,3 +34,19 @@ _ = (
   b"abc"
   b"def"
 )
+
+_ = """a""" """b"""
+
+_ = """a
+b""" """c
+d"""
+
+_ = f"""a""" f"""b"""
+
+_ = f"a" "b"
+
+_ = """a""" "b"
+
+_ = 'a' "b"
+
+_ = rf"a" rf"b"

crates/ruff/src/rules/flake8_implicit_str_concat/rules/implicit.rs

@@ -3,9 +3,10 @@ use ruff_text_size::TextRange;
 use rustpython_parser::lexer::LexResult;
 use rustpython_parser::Tok;
 
-use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_diagnostics::{AutofixKind, Diagnostic, Edit, Fix, Violation};
 use ruff_macros::{derive_message_formats, violation};
 use ruff_python_ast::source_code::Locator;
+use ruff_python_ast::str::{leading_quote, trailing_quote};
 
 use crate::rules::flake8_implicit_str_concat::settings::Settings;
 
@@ -34,10 +35,16 @@ use crate::rules::flake8_implicit_str_concat::settings::Settings;
 pub struct SingleLineImplicitStringConcatenation;
 
 impl Violation for SingleLineImplicitStringConcatenation {
+    const AUTOFIX: AutofixKind = AutofixKind::Sometimes;
+
     #[derive_message_formats]
     fn message(&self) -> String {
         format!("Implicitly concatenated string literals on one line")
     }
+
+    fn autofix_title(&self) -> Option<String> {
+        Some("Combine string literals".to_string())
+    }
 }
 
 /// ## What it does
@@ -106,12 +113,50 @@ pub(crate) fn implicit(
                     TextRange::new(a_range.start(), b_range.end()),
                 ));
             } else {
-                diagnostics.push(Diagnostic::new(
+                let mut diagnostic = Diagnostic::new(
                     SingleLineImplicitStringConcatenation,
                     TextRange::new(a_range.start(), b_range.end()),
-                ));
-            }
-        }
+                );
+
+                if let Some(fix) = concatenate_strings(*a_range, *b_range, locator) {
+                    diagnostic.set_fix(fix);
+                }
+
+                diagnostics.push(diagnostic);
+            };
+        };
     }
     diagnostics
 }
+
+fn concatenate_strings(a_range: TextRange, b_range: TextRange, locator: &Locator) -> Option<Fix> {
+    let a_text = &locator.contents()[a_range];
+    let b_text = &locator.contents()[b_range];
+
+    let a_leading_quote = leading_quote(a_text)?;
+    let b_leading_quote = leading_quote(b_text)?;
+
+    // Require, for now, that the leading quotes are the same.
+    if a_leading_quote != b_leading_quote {
+        return None;
+    }
+
+    let a_trailing_quote = trailing_quote(a_text)?;
+    let b_trailing_quote = trailing_quote(b_text)?;
+
+    // Require, for now, that the trailing quotes are the same.
+    if a_trailing_quote != b_trailing_quote {
+        return None;
+    }
+
+    let a_body = &a_text[a_leading_quote.len()..a_text.len() - a_trailing_quote.len()];
+    let b_body = &b_text[b_leading_quote.len()..b_text.len() - b_trailing_quote.len()];
+
+    let concatenation = format!("{a_leading_quote}{a_body}{b_body}{a_trailing_quote}");
+    let range = TextRange::new(a_range.start(), b_range.end());
+
+    Some(Fix::automatic(Edit::range_replacement(
+        concatenation,
+        range,
+    )))
+}

crates/ruff/src/rules/flake8_implicit_str_concat/snapshots/ruff__rules__flake8_implicit_str_concat__tests__ISC001_ISC.py.snap

@@ -1,20 +1,151 @@
 ---
 source: crates/ruff/src/rules/flake8_implicit_str_concat/mod.rs
 ---
-ISC.py:1:5: ISC001 Implicitly concatenated string literals on one line
+ISC.py:1:5: ISC001 [*] Implicitly concatenated string literals on one line
   |
 1 | _ = "a" "b" "c"
   |     ^^^^^^^ ISC001
 2 | 
 3 | _ = "abc" + "def"
   |
+  = help: Combine string literals
 
-ISC.py:1:9: ISC001 Implicitly concatenated string literals on one line
+ℹ Fix
+1   |-_ = "a" "b" "c"
+  1 |+_ = "ab" "c"
+2 2 | 
+3 3 | _ = "abc" + "def"
+4 4 | 
+
+ISC.py:1:9: ISC001 [*] Implicitly concatenated string literals on one line
   |
 1 | _ = "a" "b" "c"
   |         ^^^^^^^ ISC001
 2 | 
 3 | _ = "abc" + "def"
   |
+  = help: Combine string literals
+
+ℹ Fix
+1   |-_ = "a" "b" "c"
+  1 |+_ = "a" "bc"
+2 2 | 
+3 3 | _ = "abc" + "def"
+4 4 | 
+
+ISC.py:38:5: ISC001 [*] Implicitly concatenated string literals on one line
+   |
+36 | )
+37 | 
+38 | _ = """a""" """b"""
+   |     ^^^^^^^^^^^^^^^ ISC001
+39 | 
+40 | _ = """a
+   |
+   = help: Combine string literals
+
+ℹ Fix
+35 35 |   b"def"
+36 36 | )
+37 37 | 
+38    |-_ = """a""" """b"""
+   38 |+_ = """ab"""
+39 39 | 
+40 40 | _ = """a
+41 41 | b""" """c
+
+ISC.py:40:5: ISC001 [*] Implicitly concatenated string literals on one line
+   |
+38 |   _ = """a""" """b"""
+39 |   
+40 |   _ = """a
+   |  _____^
+41 | | b""" """c
+42 | | d"""
+   | |____^ ISC001
+43 |   
+44 |   _ = f"""a""" f"""b"""
+   |
+   = help: Combine string literals
+
+ℹ Fix
+38 38 | _ = """a""" """b"""
+39 39 | 
+40 40 | _ = """a
+41    |-b""" """c
+   41 |+bc
+42 42 | d"""
+43 43 | 
+44 44 | _ = f"""a""" f"""b"""
+
+ISC.py:44:5: ISC001 [*] Implicitly concatenated string literals on one line
+   |
+42 | d"""
+43 | 
+44 | _ = f"""a""" f"""b"""
+   |     ^^^^^^^^^^^^^^^^^ ISC001
+45 | 
+46 | _ = f"a" "b"
+   |
+   = help: Combine string literals
+
+ℹ Fix
+41 41 | b""" """c
+42 42 | d"""
+43 43 | 
+44    |-_ = f"""a""" f"""b"""
+   44 |+_ = f"""ab"""
+45 45 | 
+46 46 | _ = f"a" "b"
+47 47 | 
+
+ISC.py:46:5: ISC001 Implicitly concatenated string literals on one line
+   |
+44 | _ = f"""a""" f"""b"""
+45 | 
+46 | _ = f"a" "b"
+   |     ^^^^^^^^ ISC001
+47 | 
+48 | _ = """a""" "b"
+   |
+   = help: Combine string literals
+
+ISC.py:48:5: ISC001 Implicitly concatenated string literals on one line
+   |
+46 | _ = f"a" "b"
+47 | 
+48 | _ = """a""" "b"
+   |     ^^^^^^^^^^^ ISC001
+49 | 
+50 | _ = 'a' "b"
+   |
+   = help: Combine string literals
+
+ISC.py:50:5: ISC001 Implicitly concatenated string literals on one line
+   |
+48 | _ = """a""" "b"
+49 | 
+50 | _ = 'a' "b"
+   |     ^^^^^^^ ISC001
+51 | 
+52 | _ = rf"a" rf"b"
+   |
+   = help: Combine string literals
+
+ISC.py:52:5: ISC001 [*] Implicitly concatenated string literals on one line
+   |
+50 | _ = 'a' "b"
+51 | 
+52 | _ = rf"a" rf"b"
+   |     ^^^^^^^^^^^ ISC001
+   |
+   = help: Combine string literals
+
+ℹ Fix
+49 49 | 
+50 50 | _ = 'a' "b"
+51 51 | 
+52    |-_ = rf"a" rf"b"
+   52 |+_ = rf"ab"
 
 

crates/ruff/src/rules/flake8_implicit_str_concat/snapshots/ruff__rules__flake8_implicit_str_concat__tests__multiline_ISC001_ISC.py.snap

@@ -1,20 +1,151 @@
 ---
 source: crates/ruff/src/rules/flake8_implicit_str_concat/mod.rs
 ---
-ISC.py:1:5: ISC001 Implicitly concatenated string literals on one line
+ISC.py:1:5: ISC001 [*] Implicitly concatenated string literals on one line
   |
 1 | _ = "a" "b" "c"
   |     ^^^^^^^ ISC001
 2 | 
 3 | _ = "abc" + "def"
   |
+  = help: Combine string literals
 
-ISC.py:1:9: ISC001 Implicitly concatenated string literals on one line
+ℹ Fix
+1   |-_ = "a" "b" "c"
+  1 |+_ = "ab" "c"
+2 2 | 
+3 3 | _ = "abc" + "def"
+4 4 | 
+
+ISC.py:1:9: ISC001 [*] Implicitly concatenated string literals on one line
   |
 1 | _ = "a" "b" "c"
   |         ^^^^^^^ ISC001
 2 | 
 3 | _ = "abc" + "def"
   |
+  = help: Combine string literals
+
+ℹ Fix
+1   |-_ = "a" "b" "c"
+  1 |+_ = "a" "bc"
+2 2 | 
+3 3 | _ = "abc" + "def"
+4 4 | 
+
+ISC.py:38:5: ISC001 [*] Implicitly concatenated string literals on one line
+   |
+36 | )
+37 | 
+38 | _ = """a""" """b"""
+   |     ^^^^^^^^^^^^^^^ ISC001
+39 | 
+40 | _ = """a
+   |
+   = help: Combine string literals
+
+ℹ Fix
+35 35 |   b"def"
+36 36 | )
+37 37 | 
+38    |-_ = """a""" """b"""
+   38 |+_ = """ab"""
+39 39 | 
+40 40 | _ = """a
+41 41 | b""" """c
+
+ISC.py:40:5: ISC001 [*] Implicitly concatenated string literals on one line
+   |
+38 |   _ = """a""" """b"""
+39 |   
+40 |   _ = """a
+   |  _____^
+41 | | b""" """c
+42 | | d"""
+   | |____^ ISC001
+43 |   
+44 |   _ = f"""a""" f"""b"""
+   |
+   = help: Combine string literals
+
+ℹ Fix
+38 38 | _ = """a""" """b"""
+39 39 | 
+40 40 | _ = """a
+41    |-b""" """c
+   41 |+bc
+42 42 | d"""
+43 43 | 
+44 44 | _ = f"""a""" f"""b"""
+
+ISC.py:44:5: ISC001 [*] Implicitly concatenated string literals on one line
+   |
+42 | d"""
+43 | 
+44 | _ = f"""a""" f"""b"""
+   |     ^^^^^^^^^^^^^^^^^ ISC001
+45 | 
+46 | _ = f"a" "b"
+   |
+   = help: Combine string literals
+
+ℹ Fix
+41 41 | b""" """c
+42 42 | d"""
+43 43 | 
+44    |-_ = f"""a""" f"""b"""
+   44 |+_ = f"""ab"""
+45 45 | 
+46 46 | _ = f"a" "b"
+47 47 | 
+
+ISC.py:46:5: ISC001 Implicitly concatenated string literals on one line
+   |
+44 | _ = f"""a""" f"""b"""
+45 | 
+46 | _ = f"a" "b"
+   |     ^^^^^^^^ ISC001
+47 | 
+48 | _ = """a""" "b"
+   |
+   = help: Combine string literals
+
+ISC.py:48:5: ISC001 Implicitly concatenated string literals on one line
+   |
+46 | _ = f"a" "b"
+47 | 
+48 | _ = """a""" "b"
+   |     ^^^^^^^^^^^ ISC001
+49 | 
+50 | _ = 'a' "b"
+   |
+   = help: Combine string literals
+
+ISC.py:50:5: ISC001 Implicitly concatenated string literals on one line
+   |
+48 | _ = """a""" "b"
+49 | 
+50 | _ = 'a' "b"
+   |     ^^^^^^^ ISC001
+51 | 
+52 | _ = rf"a" rf"b"
+   |
+   = help: Combine string literals
+
+ISC.py:52:5: ISC001 [*] Implicitly concatenated string literals on one line
+   |
+50 | _ = 'a' "b"
+51 | 
+52 | _ = rf"a" rf"b"
+   |     ^^^^^^^^^^^ ISC001
+   |
+   = help: Combine string literals
+
+ℹ Fix
+49 49 | 
+50 50 | _ = 'a' "b"
+51 51 | 
+52    |-_ = rf"a" rf"b"
+   52 |+_ = rf"ab"