From 1f3102163236cb3ff6a42e1c6c3cc8d9b4aa1c22 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Wed, 13 Aug 2025 23:11:01 +0200
Subject: [PATCH] Fix wrong macro argument parsing

---
 askama_parser/src/expr.rs                     | 32 +++++++++++++++--
 ...testcase-minimized-derive-5107711304073216 |  1 +
 testing/tests/macro.rs                        | 16 +++++++++
 testing/tests/ui/macro-args-hashtag.rs        | 34 +++++++++++++++++++
 testing/tests/ui/macro-args-hashtag.stderr    | 31 +++++++++++++++++
 5 files changed, 112 insertions(+), 2 deletions(-)
 create mode 100644 fuzzing/fuzz/artifacts/derive/clusterfuzz-testcase-minimized-derive-5107711304073216
 create mode 100644 testing/tests/ui/macro-args-hashtag.rs
 create mode 100644 testing/tests/ui/macro-args-hashtag.stderr

diff --git a/askama_parser/src/expr.rs b/askama_parser/src/expr.rs
index 5301212d..f8b8d7bc 100644
--- a/askama_parser/src/expr.rs
+++ b/askama_parser/src/expr.rs
@@ -927,6 +927,35 @@ impl<'a> Suffix<'a> {
             }
         }
 
+        fn lifetime<'a>(i: &mut InputStream<'a>) -> ParseResult<'a, ()> {
+            // Before the 2021 edition, we can have whitespace characters between "r#" and the
+            // identifier so we allow it here.
+            let start = *i;
+            '\''.parse_next(i)?;
+            let Some((is_raw, identifier)) = opt(alt((
+                ('r', '#', identifier).map(|(_, _, ident)| (true, ident)),
+                (identifier, not(peek('#'))).map(|(ident, _)| (false, ident)),
+            )))
+            .parse_next(i)?
+            else {
+                return cut_error!("wrong lifetime format", **start);
+            };
+            if !is_raw {
+                if crate::is_rust_keyword(identifier) {
+                    return cut_error!(
+                        "a non-raw lifetime cannot be named like an existing keyword",
+                        **start,
+                    );
+                }
+            } else if ["Self", "self", "crate", "super", "_"].contains(&identifier) {
+                return cut_error!(format!("`{identifier}` cannot be a raw lifetime"), **start,);
+            }
+            if opt(peek('\'')).parse_next(i)?.is_some() {
+                return cut_error!("unexpected `'` after lifetime", **start);
+            }
+            Ok(())
+        }
+
         fn token<'a>(i: &mut InputStream<'a>) -> ParseResult<'a, Token> {
             // <https://doc.rust-lang.org/reference/tokens.html>
             let some_other = alt((
@@ -936,8 +965,7 @@ impl<'a> Suffix<'a> {
                 num_lit.value(Token::SomeOther),
                 // keywords + (raw) identifiers + raw strings
                 identifier_or_prefixed_string.value(Token::SomeOther),
-                // lifetimes
-                ('\'', identifier, not(peek('\''))).value(Token::SomeOther),
+                lifetime.value(Token::SomeOther),
                 // comments
                 line_comment.value(Token::SomeOther),
                 block_comment.value(Token::SomeOther),
diff --git a/fuzzing/fuzz/artifacts/derive/clusterfuzz-testcase-minimized-derive-5107711304073216 b/fuzzing/fuzz/artifacts/derive/clusterfuzz-testcase-minimized-derive-5107711304073216
new file mode 100644
index 00000000..adab7e9c
--- /dev/null
+++ b/fuzzing/fuzz/artifacts/derive/clusterfuzz-testcase-minimized-derive-5107711304073216
@@ -0,0 +1 @@
+ÿÿÿ{{z!{'r#}}}ÿ  ÿsÿ  
\ No newline at end of file
diff --git a/testing/tests/macro.rs b/testing/tests/macro.rs
index a8192578..c67696a5 100644
--- a/testing/tests/macro.rs
+++ b/testing/tests/macro.rs
@@ -630,3 +630,19 @@ fn test_macro_caller_is_defined_check() {
         "no caller defined|this time with caller"
     );
 }
+
+// This test ensures that raw lifetimes are correctly handled.
+#[test]
+fn test_macro_raw_lifetime() {
+    macro_rules! test {
+        ('r#ignore_me) => {
+            "ok"
+        };
+    }
+
+    #[derive(Template)]
+    #[template(source = r##"{{ test!('r#ignore_me) }}"##, ext = "txt")]
+    struct Foo;
+
+    assert_eq!(Foo.render().unwrap(), "ok");
+}
diff --git a/testing/tests/ui/macro-args-hashtag.rs b/testing/tests/ui/macro-args-hashtag.rs
new file mode 100644
index 00000000..d12d0c9f
--- /dev/null
+++ b/testing/tests/ui/macro-args-hashtag.rs
@@ -0,0 +1,34 @@
+// This test ensures that we have the right error if a `#` character isn't prepended by
+// a whitespace character and also that lifetimes are correctly handled.
+
+use askama::Template;
+
+#[derive(Template)]
+#[template(
+    source = r###"{{z!{'r#}}}"###,
+    ext = "html"
+)]
+struct Example;
+
+#[derive(Template)]
+#[template(
+    source = r###"{{z!{'r# y}}}"###,
+    ext = "html"
+)]
+struct Example2;
+
+#[derive(Template)]
+#[template(
+    source = r###"{{z!{'break}}}"###,
+    ext = "html"
+)]
+struct Example3;
+
+#[derive(Template)]
+#[template(
+    source = r###"{{z!{'r#self}}}"###,
+    ext = "html"
+)]
+struct Example4;
+
+fn main() {}
diff --git a/testing/tests/ui/macro-args-hashtag.stderr b/testing/tests/ui/macro-args-hashtag.stderr
new file mode 100644
index 00000000..5675bc89
--- /dev/null
+++ b/testing/tests/ui/macro-args-hashtag.stderr
@@ -0,0 +1,31 @@
+error: wrong lifetime format
+ --> <source attribute>:1:5
+       "'r#}}}"
+ --> tests/ui/macro-args-hashtag.rs:8:14
+  |
+8 |     source = r###"{{z!{'r#}}}"###,
+  |              ^^^^^^^^^^^^^^^^^^^^
+
+error: wrong lifetime format
+ --> <source attribute>:1:5
+       "'r# y}}}"
+  --> tests/ui/macro-args-hashtag.rs:15:14
+   |
+15 |     source = r###"{{z!{'r# y}}}"###,
+   |              ^^^^^^^^^^^^^^^^^^^^^^
+
+error: a non-raw lifetime cannot be named like an existing keyword
+ --> <source attribute>:1:5
+       "'break}}}"
+  --> tests/ui/macro-args-hashtag.rs:22:14
+   |
+22 |     source = r###"{{z!{'break}}}"###,
+   |              ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: `self` cannot be a raw lifetime
+ --> <source attribute>:1:5
+       "'r#self}}}"
+  --> tests/ui/macro-args-hashtag.rs:29:14
+   |
+29 |     source = r###"{{z!{'r#self}}}"###,
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^