Round-trip parsing and output generation causes difference in parsed result

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#165 3 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
rust
Domain
web-dev

Research direction

Start by running the Rust reproducer from the issue and compare the two token lists for the shown input. Trace the token parsing and ToCss serialization paths involved; the fix is complete when parsing the generated string preserves the original parsed result and the regression is covered by a test.

Written by the indexing model from the issue text.

Description

Found this while fuzzing.

extern crate cssparser;

use cssparser::ToCss;

fn main() {
    let input = "\\\n3:\'\\\x0c";
    println!("input:\n\t{:?}", input);

    let mut parser_input = cssparser::ParserInput::new(input);
    let mut parser = cssparser::Parser::new(&mut parser_input);
    let tokens = parser
        .next_including_whitespace_and_comments()
        .into_iter()
        .collect::<Vec<_>>();
    println!("tokens:\n\t{:?}", tokens);

    let str2 = tokens.iter().map(|t| t.to_css_string()).collect::<String>();
    println!("tokens to string:\n\t{:?}", str2);

    let mut parser_input = cssparser::ParserInput::new(&str2);
    let mut parser = cssparser::Parser::new(&mut parser_input);
    let tokens2 = parser
        .next_including_whitespace_and_comments()
        .into_iter()
        .collect::<Vec<_>>();
    println!("tokens to string to tokens:\n\t{:?}", tokens2);
}

input:
	"\\\n3:\'\\\u{c}"
tokens:
	[Delim('\\')]
tokens to string:
	"\\"
tokens to string to tokens:
	[Ident("�")]
Dominant language
Rust
Stars
869
Forks
152
Avg merge
15h 8m
Merged PRs (30d)
12

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