parser: recognize comments in macro calls

Fixes issue <https://issues.oss-fuzz.com/issues/425145246>

askama_parser/src/expr.rs

@@ -4,9 +4,10 @@ use std::str;
 use winnow::Parser;
 use winnow::ascii::digit1;
 use winnow::combinator::{
-    alt, cut_err, fail, not, opt, peek, preceded, repeat, separated, terminated,
+    alt, cut_err, empty, fail, not, opt, peek, preceded, repeat, separated, terminated,
 };
 use winnow::error::ParserError as _;
+use winnow::token::take_until;
 
 use crate::node::CondTest;
 use crate::{
@@ -780,6 +781,9 @@ impl<'a> Suffix<'a> {
                 identifier_or_prefixed_string.value(Token::SomeOther),
                 // lifetimes
                 ('\'', identifier, not(peek('\''))).value(Token::SomeOther),
+                // comments
+                line_comment.value(Token::SomeOther),
+                block_comment.value(Token::SomeOther),
                 // punctuations
                 punctuation.value(Token::SomeOther),
                 hash,
@@ -787,6 +791,46 @@ impl<'a> Suffix<'a> {
             alt((open.map(Token::Open), close.map(Token::Close), some_other)).parse_next(i)
         }
 
+        fn line_comment<'a>(i: &mut &'a str) -> ParseResult<'a, ()> {
+            let start = "//".parse_next(i)?;
+            let is_doc_comment = alt((
+                ('/', not(peek('/'))).value(true),
+                '!'.value(true),
+                empty.value(false),
+            ))
+            .parse_next(i)?;
+            if opt(take_until(.., '\n')).parse_next(i)?.is_none() {
+                return Err(winnow::error::ErrMode::Cut(ErrorContext::new(
+                    format!(
+                        "you are probably missing a line break to end {}comment",
+                        if is_doc_comment { "doc " } else { "" }
+                    ),
+                    start,
+                )));
+            }
+            Ok(())
+        }
+
+        fn block_comment<'a>(i: &mut &'a str) -> ParseResult<'a, ()> {
+            let start = "/*".parse_next(i)?;
+            let is_doc_comment = alt((
+                ('*', not(peek('*'))).value(true),
+                '!'.value(true),
+                empty.value(false),
+            ))
+            .parse_next(i)?;
+            if opt(take_until(.., "*/")).parse_next(i)?.is_none() {
+                return Err(winnow::error::ErrMode::Cut(ErrorContext::new(
+                    format!(
+                        "missing `*/` to close block {}comment",
+                        if is_doc_comment { "doc " } else { "" }
+                    ),
+                    start,
+                )));
+            }
+            Ok(())
+        }
+
         fn identifier_or_prefixed_string<'a>(i: &mut &'a str) -> ParseResult<'a, ()> {
             // <https://doc.rust-lang.org/reference/tokens.html#r-lex.token.literal.str-raw.syntax>
 

askama_parser/src/tests.rs

@@ -1441,3 +1441,70 @@ fn macro_calls_can_have_raw_prefixes() {
         )],
     );
 }
+
+#[test]
+fn macro_comments_in_macro_calls() {
+    // Related to issue <https://github.com/askama-rs/askama/issues/475>.
+    let syntax = Syntax::default();
+
+    assert!(Ast::from_str("{{ e!(// hello) }}", None, &syntax).is_err());
+    assert!(Ast::from_str("{{ e!(/// hello) }}", None, &syntax).is_err());
+    assert!(Ast::from_str("{{ e!(// hello)\n }}", None, &syntax).is_err());
+    assert!(Ast::from_str("{{ e!(/// hello)\n }}", None, &syntax).is_err());
+
+    assert_eq!(
+        Ast::from_str("{{ e!(// hello\n) }}", None, &syntax)
+            .unwrap()
+            .nodes,
+        vec![Node::Expr(
+            Ws(None, None),
+            WithSpan::no_span(Expr::RustMacro(vec!["e"], "// hello\n")),
+        )],
+    );
+    assert_eq!(
+        Ast::from_str("{{ e!(/// hello\n) }}", None, &syntax)
+            .unwrap()
+            .nodes,
+        vec![Node::Expr(
+            Ws(None, None),
+            WithSpan::no_span(Expr::RustMacro(vec!["e"], "/// hello\n")),
+        )],
+    );
+    assert_eq!(
+        Ast::from_str("{{ e!(//! hello\n) }}", None, &syntax)
+            .unwrap()
+            .nodes,
+        vec![Node::Expr(
+            Ws(None, None),
+            WithSpan::no_span(Expr::RustMacro(vec!["e"], "//! hello\n")),
+        )],
+    );
+
+    assert_eq!(
+        Ast::from_str("{{ e!(/* hello */) }}", None, &syntax)
+            .unwrap()
+            .nodes,
+        vec![Node::Expr(
+            Ws(None, None),
+            WithSpan::no_span(Expr::RustMacro(vec!["e"], "/* hello */")),
+        )],
+    );
+    assert_eq!(
+        Ast::from_str("{{ e!(/** hello */) }}", None, &syntax)
+            .unwrap()
+            .nodes,
+        vec![Node::Expr(
+            Ws(None, None),
+            WithSpan::no_span(Expr::RustMacro(vec!["e"], "/** hello */")),
+        )],
+    );
+    assert_eq!(
+        Ast::from_str("{{ e!(/*! hello */) }}", None, &syntax)
+            .unwrap()
+            .nodes,
+        vec![Node::Expr(
+            Ws(None, None),
+            WithSpan::no_span(Expr::RustMacro(vec!["e"], "/*! hello */")),
+        )],
+    );
+}

fuzzing/fuzz/artifacts/derive/clusterfuzz-testcase-minimized-derive-6051930453639168

@@ -0,0 +1 @@
+˙˙˙{{e!{//}}}˙˙˙˙s˙  

testing/tests/ui/comments-in-macro-calls.rs

@@ -0,0 +1,41 @@
+use askama::Template;
+
+// Regression test for <https://issues.oss-fuzz.com/issues/425145246>.
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ e!(// hello) }}")]
+struct LineComment;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ e!(// hello)\n}}")]
+struct LineComment2;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ e!(/* hello) }}")]
+struct BlockComment;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ e!(/// hello) }}")]
+struct OuterLineDoc;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ e!(/// hello)\n}}")]
+struct OuterLineDoc2;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ e!(/** hello) }}")]
+struct OuterBlockDoc;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ e!(//! hello) }}")]
+struct InnerLineDoc;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ e!(//! hello)\n}}")]
+struct InnerLineDoc2;
+
+#[derive(Template)]
+#[template(ext = "html", source = "{{ e!(/*! hello) }}")]
+struct InnerBlockDoc;
+
+fn main() {}

testing/tests/ui/comments-in-macro-calls.stderr

@@ -0,0 +1,71 @@
+error: you are probably missing a line break to end comment
+ --> <source attribute>:1:6
+       "// hello) }}"
+ --> tests/ui/comments-in-macro-calls.rs:6:35
+  |
+6 | #[template(ext = "html", source = "{{ e!(// hello) }}")]
+  |                                   ^^^^^^^^^^^^^^^^^^^^
+
+error: expected `)` but found `}`
+ --> <source attribute>:1:15
+       "}}"
+  --> tests/ui/comments-in-macro-calls.rs:10:35
+   |
+10 | #[template(ext = "html", source = "{{ e!(// hello)\n}}")]
+   |                                   ^^^^^^^^^^^^^^^^^^^^^
+
+error: missing `*/` to close block comment
+ --> <source attribute>:1:6
+       "/* hello) }}"
+  --> tests/ui/comments-in-macro-calls.rs:14:35
+   |
+14 | #[template(ext = "html", source = "{{ e!(/* hello) }}")]
+   |                                   ^^^^^^^^^^^^^^^^^^^^
+
+error: you are probably missing a line break to end doc comment
+ --> <source attribute>:1:6
+       "/// hello) }}"
+  --> tests/ui/comments-in-macro-calls.rs:18:35
+   |
+18 | #[template(ext = "html", source = "{{ e!(/// hello) }}")]
+   |                                   ^^^^^^^^^^^^^^^^^^^^^
+
+error: expected `)` but found `}`
+ --> <source attribute>:1:16
+       "}}"
+  --> tests/ui/comments-in-macro-calls.rs:22:35
+   |
+22 | #[template(ext = "html", source = "{{ e!(/// hello)\n}}")]
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^
+
+error: missing `*/` to close block doc comment
+ --> <source attribute>:1:6
+       "/** hello) }}"
+  --> tests/ui/comments-in-macro-calls.rs:26:35
+   |
+26 | #[template(ext = "html", source = "{{ e!(/** hello) }}")]
+   |                                   ^^^^^^^^^^^^^^^^^^^^^
+
+error: you are probably missing a line break to end doc comment
+ --> <source attribute>:1:6
+       "//! hello) }}"
+  --> tests/ui/comments-in-macro-calls.rs:30:35
+   |
+30 | #[template(ext = "html", source = "{{ e!(//! hello) }}")]
+   |                                   ^^^^^^^^^^^^^^^^^^^^^
+
+error: expected `)` but found `}`
+ --> <source attribute>:1:16
+       "}}"
+  --> tests/ui/comments-in-macro-calls.rs:34:35
+   |
+34 | #[template(ext = "html", source = "{{ e!(//! hello)\n}}")]
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^
+
+error: missing `*/` to close block doc comment
+ --> <source attribute>:1:6
+       "/*! hello) }}"
+  --> tests/ui/comments-in-macro-calls.rs:38:35
+   |
+38 | #[template(ext = "html", source = "{{ e!(/*! hello) }}")]
+   |                                   ^^^^^^^^^^^^^^^^^^^^^