From 0f21f07f81c59ddb2865935f0d531977ac52ce80 Mon Sep 17 00:00:00 2001
From: Dhruv Manilawala <dhruvmanila@gmail.com>
Date: Thu, 14 Sep 2023 12:52:44 +0530
Subject: [PATCH] Allow `NUL` character in f-strings

---
 crates/ruff_python_parser/src/lexer.rs        | 11 +++++++-
 ...__lexer__tests__fstring_with_nul_char.snap | 25 +++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)
 create mode 100644 crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_with_nul_char.snap

diff --git a/crates/ruff_python_parser/src/lexer.rs b/crates/ruff_python_parser/src/lexer.rs
index ab41477d77951..b8abdc411e9fa 100644
--- a/crates/ruff_python_parser/src/lexer.rs
+++ b/crates/ruff_python_parser/src/lexer.rs
@@ -552,7 +552,10 @@ impl<'source> Lexer<'source> {
 
         loop {
             match self.cursor.first() {
-                EOF_CHAR => {
+                // The condition is to differentiate between the `NUL` (`\0`) character
+                // in the source code and the one returned by `self.cursor.first()` when
+                // we reach the end of the source code.
+                EOF_CHAR if self.cursor.is_eof() => {
                     let error = if fstring.is_triple_quoted() {
                         FStringErrorType::UnterminatedTripleQuotedString
                     } else {
@@ -2020,6 +2023,12 @@ f"{(lambda x:{x})}"
         assert_debug_snapshot!(lex_source(source));
     }
 
+    #[test]
+    fn test_fstring_with_nul_char() {
+        let source = r"f'\0'";
+        assert_debug_snapshot!(lex_source(source));
+    }
+
     fn lex_fstring_error(source: &str) -> FStringErrorType {
         match lex(source, Mode::Module).find_map(std::result::Result::err) {
             Some(err) => match err.error {
diff --git a/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_with_nul_char.snap b/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_with_nul_char.snap
new file mode 100644
index 0000000000000..667d1897ecbcd
--- /dev/null
+++ b/crates/ruff_python_parser/src/snapshots/ruff_python_parser__lexer__tests__fstring_with_nul_char.snap
@@ -0,0 +1,25 @@
+---
+source: crates/ruff_python_parser/src/lexer.rs
+expression: lex_source(source)
+---
+[
+    (
+        FStringStart,
+        0..2,
+    ),
+    (
+        FStringMiddle {
+            value: "\\0",
+            is_raw: false,
+        },
+        2..4,
+    ),
+    (
+        FStringEnd,
+        4..5,
+    ),
+    (
+        Newline,
+        5..5,
+    ),
+]