Merge pull request #60 from amazon-ion/broken-pipe

Handle BrokenPipe gracefully

src/bin/ion/main.rs

@@ -3,14 +3,28 @@ mod commands;
 use crate::commands::beta::BetaNamespace;
 use anyhow::Result;
 use commands::IonCliCommand;
+use ion_rs::IonError;
+use std::io::ErrorKind;
 
 use crate::commands::dump::DumpCommand;
 
 fn main() -> Result<()> {
     let root_command = RootCommand;
     let args = root_command.clap_command().get_matches();
     let mut command_path: Vec<String> = vec![root_command.name().to_owned()];
-    root_command.run(&mut command_path, &args)
+
+    if let Err(e) = root_command.run(&mut command_path, &args) {
+        match e.downcast_ref::<IonError>() {
+            // If `ion-cli` is being invoked as part of a pipeline we want to allow the pipeline to
+            // to shut off without printing an error to stderr
+            Some(IonError::IoError { source }) if source.kind() == ErrorKind::BrokenPipe => {
+                return Ok(())
+            }
+            _ => return Err(e),
+        }
+    };
+
+    Ok(())
 }
 
 pub struct RootCommand;