CLI support for piping

[oylenshpeegul]

Resolves #375

src/main.rs: made input_file optional and use stdin and a fake name if it's None
Cargo.toml: added new cli dependency on atty for detecting pipe
rust-toolchain.toml: bumped version of Rust for stable std::io::read_to_string
tests/cli_integration_tests.rs: removed test for no_input_file

[devongovett]

Thank you!

[roman01la]

Is there a test case for stdin input? It doesn't seem to work for me, unless I'm doing something wrong :(

[oylenshpeegul]

What did you try? I just built the latest version and this seems to work for me.

❯ git clone https://github.com/parcel-bundler/lightningcss.git
❯ cd lightningcss
❯ cargo build --features=cli --release
...
❯ $CARGO_TARGET_DIR/release/lightningcss -h
...
❯ cat tests/testdata/a.css 
@import "b.css";

.a {
  width: 32px;
}

❯ cat tests/testdata/a.css | $CARGO_TARGET_DIR/release/lightningcss --minify
@import "b.css";.a{width:32px}

If it detects that STDIN has not been redirected, it gives an error rather than silently wait for input.

❯ $CARGO_TARGET_DIR/release/lightningcss 
Error: Custom { kind: Other, error: "Not reading from stdin as it was not redirected" }

[roman01la]

@oylenshpeegul Ignore my stupidity, sorry :) It works flawlessly!

[oylenshpeegul]

No worries! Have a nice day.