CLI support for piping

Cargo.toml

@@ -30,7 +30,7 @@ crate-type = ["rlib"]
 default = ["bundler", "grid", "nodejs", "sourcemap"]
 browserslist = ["browserslist-rs"]
 bundler = ["dashmap", "sourcemap", "rayon"]
-cli = ["clap", "serde_json", "browserslist", "jemallocator"]
+cli = ["atty", "clap", "serde_json", "browserslist", "jemallocator"]
 grid = []
 jsonschema = ["schemars", "serde", "parcel_selectors/jsonschema"]
 nodejs = ["dep:serde"]
@@ -51,6 +51,7 @@ lazy_static = "1.4.0"
 const-str = "0.3.1"
 pathdiff = "0.2.1"
 # CLI deps
+atty = { version = "0.2", optional = true }
 clap = { version = "3.0.6", features = ["derive"], optional = true }
 browserslist-rs = { version = "0.7.0", optional = true }
 rayon = { version = "1.5.1", optional = true }

rust-toolchain.toml

@@ -1,3 +1,3 @@
 [toolchain]
-channel = "1.63.0"
+channel = "1.65.0"
 components = ["rustfmt", "clippy"]

src/main.rs

@@ -1,3 +1,4 @@
+use atty::Stream;
 use clap::{ArgGroup, Parser};
 use lightningcss::bundler::{Bundler, FileProvider};
 use lightningcss::stylesheet::{MinifyOptions, ParserOptions, PrinterOptions, StyleSheet};
@@ -18,9 +19,9 @@ static GLOBAL: jemallocator::Jemalloc = jemallocator::Jemalloc;
       .args(&["targets", "browserslist"]),
 ))]
 struct CliArgs {
-  /// Target CSS file
+  /// Target CSS file (default: stdin)
   #[clap(value_parser)]
-  input_file: String,
+  input_file: Option<String>,
   /// Destination file for the output
   #[clap(short, long, group = "output_file", value_parser)]
   output_file: Option<String>,
@@ -67,13 +68,36 @@ struct SourceMapJson<'a> {
 
 pub fn main() -> Result<(), std::io::Error> {
   let cli_args = CliArgs::parse();
-  let source = fs::read_to_string(&cli_args.input_file)?;
-
   let project_root = std::env::current_dir()?;
-  let absolute_path = fs::canonicalize(&cli_args.input_file)?;
-  let filename = pathdiff::diff_paths(absolute_path, &project_root).unwrap();
-  let filename = filename.to_str().unwrap();
 
+  // If we're given an input file, read from it and adjust its name.
+  //
+  // If we're not given an input file and stdin was redirected, read
+  // from it and create a fake name. Return an error if stdin was not
+  // redirected (otherwise the program will hang waiting for input).
+  //
+  let (filename, source) = match &cli_args.input_file {
+    Some(f) => {
+      let absolute_path = fs::canonicalize(f)?;
+      let filename = pathdiff::diff_paths(absolute_path, &project_root).unwrap();
+      let filename = filename.to_string_lossy().into_owned();
+      let contents = fs::read_to_string(f)?;
+      (filename, contents)
+    }
+    None => {
+      // Don't silently wait for input if stdin was not redirected.
+      if atty::is(Stream::Stdin) {
+        return Err(io::Error::new(
+          io::ErrorKind::Other,
+          "Not reading from stdin as it was not redirected",
+        ));
+      }
+      let filename = format!("stdin-{}", std::process::id());
+      let contents = io::read_to_string(io::stdin())?;
+      (filename, contents)
+    }
+  };
+
   let css_modules = if let Some(_) = cli_args.css_modules {
     let pattern = if let Some(pattern) = cli_args.css_modules_pattern.as_ref() {
       match lightningcss::css_modules::Pattern::parse(pattern) {
@@ -121,13 +145,13 @@ pub fn main() -> Result<(), std::io::Error> {
 
     let mut stylesheet = if cli_args.bundle {
       let mut bundler = Bundler::new(&fs, source_map.as_mut(), options);
-      bundler.bundle(Path::new(&cli_args.input_file)).unwrap()
+      bundler.bundle(Path::new(&filename)).unwrap()
     } else {
       if let Some(sm) = &mut source_map {
         sm.add_source(&filename);
         let _ = sm.set_source_content(0, &source);
       }
-      options.filename = filename.to_owned();
+      options.filename = filename;
       StyleSheet::parse(&source, options).unwrap()
     };
 

tests/cli_integration_tests.rs

@@ -154,16 +154,6 @@ fn valid_input_file() -> Result<(), Box<dyn std::error::Error>> {
   Ok(())
 }
 
-#[test]
-fn no_input_file() -> Result<(), Box<dyn std::error::Error>> {
-  let mut cmd = Command::cargo_bin("lightningcss")?;
-  cmd.assert().failure().stderr(predicate::str::contains(
-    "The following required arguments were not provided:\n    <INPUT_FILE>",
-  ));
-
-  Ok(())
-}
-
 #[test]
 fn empty_input_file() -> Result<(), Box<dyn std::error::Error>> {
   let file = assert_fs::NamedTempFile::new("test.css")?;