Why adding space to slint file, cause running 8s build script?

[qarmin]

After first full cargo check build, adding single space in slint file and then running again cargo check takes 30 seconds.

~20 seconds is related with rust, but ~7 seconds comes from build script

A little strange that most of the time takes std::io::Write::write_fmt inside compile_with_config function and when looking at flamegraph I see hundreds of operations on files.

Is this normal behavior?

[qarmin]

So I think that here should be used buffered file operation, which should decrease time

slint/api/rs/build/lib.rs

Lines 357 to 358 in d1529af

	let file = std::fs::File::create(&output_file_path).map_err(CompileError::SaveError)?;
	let mut code_formatter = CodeFormatter::new(file);

[qarmin]

Simple changing

 let file = std::fs::File::create(&output_file_path).map_err(CompileError::SaveError)?; 
 let mut code_formatter = CodeFormatter::new(file); 

into

    let file = std::fs::File::create(&output_file_path).map_err(CompileError::SaveError)?;
    let buffer = std::io::BufWriter::new(file);
    let mut code_formatter = CodeFormatter::new(buffer);

decreased build script time from ~8s to 2s

[ogoffart]

Thanks a lot for doing the profiling and figuring out the problem.

Someone did contribute a change in #4217