CLI support for piping

[jfbrennan]

The CLI does not seem to support piping. I'm trying:

postcss ./src/all.css | lightningcss --minify -o ./dist/min.css

and I get

error: The following required arguments were not provided:
    <INPUT_FILE>

Being able to pipe output from one tool into Lightning CSS for minification would be greatly appreciated (or tell me what I'm doing wrong 🤗).

And yes I understand Lightning CSS wants to be my PostCSS too, but I refuse to mix tools like that. Never works correctly. Decoupled single-purpose tools are a must imo.

[devongovett]

Seems like a good feature to me!

[oylenshpeegul]

Since std::io::read_to_string was stabilized in Rust 1.65, getting the contents could be as simple as changing

  let source = fs::read_to_string(&cli_args.input_file)?;

to

  let source = match &cli_args.input_file {
    Some(f) => fs::read_to_string(f)?,
    None => io::read_to_string(io::stdin())?,
  };

if the channel were bumped up in rust-toolchain.toml.

However, cli_args.input_file appears in a couple of other places, so we can't just change it to an Option without deciding what to use for a name in those cases when it is None. It looks like options.filename is only used to write error messages, so perhaps substituting something like "STDIN" would be appropriate there. I'm not sure what do do about

      bundler.bundle(Path::new(&cli_args.input_file)).unwrap()

Would substituting a fake name that is not a path on the filesystem be appropriate here?

[devongovett]

Yeah a fake name should be fine. The filename is used in error messages and source maps.