From e91ffe3e93a1c7c8be6b1fa6eeaf21f3c82b8ff5 Mon Sep 17 00:00:00 2001
From: Dhruv Manilawala <dhruvmanila@gmail.com>
Date: Sun, 1 Oct 2023 07:58:20 +0530
Subject: [PATCH] Consume the escaped Windows newline (`\r\n`) for
 `FStringMiddle` (#7722)

## Summary

This PR fixes a bug where if a Windows newline (`\r\n`) character was
escaped, then only the `\r` was consumed and not `\n` leading to an
unterminated string error.

## Test Plan

Add new test cases to check the newline escapes.

fixes: #7632
---
 crates/ruff_python_parser/src/lexer.rs        | 28 +++++++++++++++++--
 ...__fstring_single_quote_escape_mac_eol.snap | 25 +++++++++++++++++
 ..._fstring_single_quote_escape_unix_eol.snap | 25 +++++++++++++++++
 ...tring_single_quote_escape_windows_eol.snap | 25 +++++++++++++++++
 4 files changed, 101 insertions(+), 2 deletions(-)
 create mode 100644 crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_mac_eol.snap
 create mode 100644 crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_unix_eol.snap
 create mode 100644 crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_windows_eol.snap

diff --git a/crates/ruff_python_parser/src/lexer.rs b/crates/ruff_python_parser/src/lexer.rs
index 5fca16e6f2fc2..c2aa3772898fe 100644
--- a/crates/ruff_python_parser/src/lexer.rs
+++ b/crates/ruff_python_parser/src/lexer.rs
@@ -584,7 +584,7 @@ impl<'source> Lexer<'source> {
                         location: self.offset(),
                     });
                 }
-                '\n' if !fstring.is_triple_quoted() => {
+                '\n' | '\r' if !fstring.is_triple_quoted() => {
                     return Err(LexicalError {
                         error: LexicalErrorType::FStringError(FStringErrorType::UnterminatedString),
                         location: self.offset(),
@@ -603,7 +603,11 @@ impl<'source> Lexer<'source> {
                         }
                     }
                     // Consume the escaped character.
-                    self.cursor.bump();
+                    if self.cursor.eat_char('\r') {
+                        self.cursor.eat_char('\n');
+                    } else {
+                        self.cursor.bump();
+                    }
                 }
                 quote @ ('\'' | '"') if quote == fstring.quote_char() => {
                     if let Some(triple_quotes) = fstring.triple_quotes() {
@@ -1983,6 +1987,26 @@ def f(arg=%timeit a = b):
         assert_debug_snapshot!(lex_source(source));
     }
 
+    fn fstring_single_quote_escape_eol(eol: &str) -> Vec<Spanned> {
+        let source = format!(r"f'text \{eol} more text'");
+        lex_source(&source)
+    }
+
+    #[test]
+    fn test_fstring_single_quote_escape_unix_eol() {
+        assert_debug_snapshot!(fstring_single_quote_escape_eol(UNIX_EOL));
+    }
+
+    #[test]
+    fn test_fstring_single_quote_escape_mac_eol() {
+        assert_debug_snapshot!(fstring_single_quote_escape_eol(MAC_EOL));
+    }
+
+    #[test]
+    fn test_fstring_single_quote_escape_windows_eol() {
+        assert_debug_snapshot!(fstring_single_quote_escape_eol(WINDOWS_EOL));
+    }
+
     #[test]
     fn test_fstring_escape() {
         let source = r#"f"\{x:\"\{x}} \"\"\
diff --git a/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_mac_eol.snap b/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_mac_eol.snap
new file mode 100644
index 0000000000000..c955bded5f680
--- /dev/null
+++ b/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_mac_eol.snap
@@ -0,0 +1,25 @@
+---
+source: crates/ruff_python_parser/src/lexer.rs
+expression: fstring_single_quote_escape_eol(MAC_EOL)
+---
+[
+    (
+        FStringStart,
+        0..2,
+    ),
+    (
+        FStringMiddle {
+            value: "text \\\r more text",
+            is_raw: false,
+        },
+        2..19,
+    ),
+    (
+        FStringEnd,
+        19..20,
+    ),
+    (
+        Newline,
+        20..20,
+    ),
+]
diff --git a/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_unix_eol.snap b/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_unix_eol.snap
new file mode 100644
index 0000000000000..0b30f70577f83
--- /dev/null
+++ b/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_unix_eol.snap
@@ -0,0 +1,25 @@
+---
+source: crates/ruff_python_parser/src/lexer.rs
+expression: fstring_single_quote_escape_eol(UNIX_EOL)
+---
+[
+    (
+        FStringStart,
+        0..2,
+    ),
+    (
+        FStringMiddle {
+            value: "text \\\n more text",
+            is_raw: false,
+        },
+        2..19,
+    ),
+    (
+        FStringEnd,
+        19..20,
+    ),
+    (
+        Newline,
+        20..20,
+    ),
+]
diff --git a/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_windows_eol.snap b/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_windows_eol.snap
new file mode 100644
index 0000000000000..e7b88d9f94b7f
--- /dev/null
+++ b/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_single_quote_escape_windows_eol.snap
@@ -0,0 +1,25 @@
+---
+source: crates/ruff_python_parser/src/lexer.rs
+expression: fstring_single_quote_escape_eol(WINDOWS_EOL)
+---
+[
+    (
+        FStringStart,
+        0..2,
+    ),
+    (
+        FStringMiddle {
+            value: "text \\\r\n more text",
+            is_raw: false,
+        },
+        2..20,
+    ),
+    (
+        FStringEnd,
+        20..21,
+    ),
+    (
+        Newline,
+        21..21,
+    ),
+]