Implement pipe mode for when there are no arguments

src/bin/stdecor.rs

@@ -14,6 +14,11 @@ async fn main() -> Result<(), Box<dyn Error>> {
         .with_env_filter(tracing_subscriber::EnvFilter::from_default_env())
         .init();
     let args = stdecor::cli::Cli::parse();
-    let exitstatus = stdecor::runner::run(&args).await?;
-    process::exit(exitstatus.code().unwrap_or(0));
+    if args.command.is_empty() {
+        stdecor::runner::pipe(&args).await?;
+        Ok(())
+    } else {
+        let exitstatus = stdecor::runner::run(&args).await?;
+        process::exit(exitstatus.code().unwrap_or(0));
+    }
 }

src/cli.rs

@@ -15,7 +15,6 @@ pub struct Cli {
     #[arg(short, long, default_value_t = false)]
     pub date: bool,
 
-    /// The command to run
-    #[clap(required = true)]
+    /// The command to run; use stdin if empty (pipe mode)
     pub command: Vec<String>,
 }

src/runner.rs

@@ -7,9 +7,10 @@ use color_eyre::{eyre::eyre, Result};
 use std::convert::TryFrom;
 use std::process::ExitStatus;
 use std::process::Stdio;
-use tokio::io::{self, AsyncWriteExt};
+use tokio::io::{self, AsyncBufReadExt, AsyncWriteExt, BufReader};
 use tokio::process::Command;
 use tokio_process_stream as tps;
+use tokio_stream::wrappers::LinesStream;
 use tokio_stream::StreamExt;
 
 use crate::cli::Cli;
@@ -65,3 +66,18 @@ pub async fn run(cli: &Cli) -> Result<ExitStatus> {
     }
     Err(eyre!("stream exhausted without a \"done\" element"))
 }
+
+#[tracing::instrument]
+pub async fn pipe(cli: &Cli) -> Result<()> {
+    let prefix_static = if let Some(prefix) = &cli.prefix {
+        format!("{} ", prefix)
+    } else {
+        "".to_string()
+    };
+    let mut stdin_lines = LinesStream::new(BufReader::new(io::stdin()).lines());
+    let mut stdout = io::stdout();
+    while let Some(line) = stdin_lines.next().await {
+        do_write(&mut stdout, &prefix_static, cli.date, &line?).await?;
+    }
+    Ok(())
+}