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SWC Community•2mo ago
Shahryar

How can keep css comments after codegen?

Hello friends, in rust I can not be able to keep comments for a css file or content for example as you see I return the comments in lexer Some(&comments), but it deletes the comments 
pub fn parse(
    file_content: &str,
) -> Result<(Stylesheet, SingleThreadedComments, Lrc<SourceMap>), String> {
    let cm: Lrc<SourceMap> = Default::default();
    let fm = cm.new_source_file(FileName::Anon.into(), file_content.into());

    let comments = SingleThreadedComments::default();

    let lexer = Lexer::new(
        SourceFileInput::from(&*fm),
        Some(&comments),
        ParserConfig::default(),
    );

    let mut parser = Parser::new(lexer, ParserConfig::default());

    let stylesheet = match parser.parse_all() {
        Ok(s) => s,
        Err(_) => {
            return Err("Failed to parse CSS".to_string());
        }
    };

    Ok((stylesheet, comments, cm))
}
pub fn parse(
    file_content: &str,
) -> Result<(Stylesheet, SingleThreadedComments, Lrc<SourceMap>), String> {
    let cm: Lrc<SourceMap> = Default::default();
    let fm = cm.new_source_file(FileName::Anon.into(), file_content.into());

    let comments = SingleThreadedComments::default();

    let lexer = Lexer::new(
        SourceFileInput::from(&*fm),
        Some(&comments),
        ParserConfig::default(),
    );

    let mut parser = Parser::new(lexer, ParserConfig::default());

    let stylesheet = match parser.parse_all() {
        Ok(s) => s,
        Err(_) => {
            return Err("Failed to parse CSS".to_string());
        }
    };

    Ok((stylesheet, comments, cm))
}
my css codegen: 
let mut output = String::new();
    {
        let mut writer = BasicCssWriter::new(&mut output, None, Default::default());
        let mut gen = CodeGenerator::new(&mut writer, CodegenConfig { minify: false });
        gen.emit(&stylesheet).expect("Failed to generate CSS");
    }

    Ok(output)
let mut output = String::new();
    {
        let mut writer = BasicCssWriter::new(&mut output, None, Default::default());
        let mut gen = CodeGenerator::new(&mut writer, CodegenConfig { minify: false });
        gen.emit(&stylesheet).expect("Failed to generate CSS");
    }

    Ok(output)
Thank you in advance --- Example: 
let css_code = r#"
            @import "reset.css";
            /* This file is for your main application CSS */
            body { color: black; }
        "#;

        let new_imports = r#"
            @import "theme.css";
            @import "reset.css";
            @import "custom.css";
        "#;

        let result = insert_import_to_ast(css_code, new_imports).unwrap();
        println!("{}", result);
let css_code = r#"
            @import "reset.css";
            /* This file is for your main application CSS */
            body { color: black; }
        "#;

        let new_imports = r#"
            @import "theme.css";
            @import "reset.css";
            @import "custom.css";
        "#;

        let result = insert_import_to_ast(css_code, new_imports).unwrap();
        println!("{}", result);
#### Returns 
@import "theme.css";
@import "custom.css";
@import "reset.css";
body {
  color: black;
}
@import "theme.css";
@import "custom.css";
@import "reset.css";
body {
  color: black;
}
4 Replies
Shahryar
ShahryarOP•2mo ago
🥲 🥲 No one has experience with it?
Levi
Levi•2mo ago
Have you tried it on SWC playground (if that supports css), or in the cli, and see if it works there? If it does, you should be able to see how it does it in the Rust code Not many people are using the Rust API for codegen it seems, so best to look at the Rust code it uses internally to see how it does it
Shahryar
ShahryarOP•2mo ago
Hi dear @Levi yes, i did. But the playground just supports js not css. I tried to find inside code but I was not successful 😔 unfortunately
Levi
Levi•2mo ago
did you try the cli? to see if it's possible to keep comments in css i dont know anything about the css implementation, maybe it's not possible because you would need to pass comments into the code generator somewhere, i think

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