rustfmt --check: handle writing to a broken pipe gracefully

src/bin/main.rs

@@ -43,7 +43,13 @@ fn main() {
         }
     };
     // Make sure standard output is flushed before we exit.
-    std::io::stdout().flush().unwrap();
+    // Silently ignore broken pipe errors, but any other errors are unexpected.
+    match std::io::stdout().flush() {
+        Err(e) if e.kind() != io::ErrorKind::BrokenPipe => {
+            panic!("flushing stdout failed: unexpected error: {:?}", e)
+        }
+        _ => {}
+    };
 
     // Exit with given exit code.
     //

src/rustfmt_diff.rs

@@ -164,11 +164,29 @@ impl OutputWriter {
         match &mut self.terminal {
             Some(ref mut t) => {
                 if let Some(color) = color {
-                    t.fg(color).unwrap();
+                    match t.fg(color) {
+                        // If writing to a broken pipe, there is no reason to continue.
+                        // Any other error is unexpected, however.
+                        Err(term::Error::Io(e)) if e.kind() == io::ErrorKind::BrokenPipe => {
+                            std::process::exit(1);
+                        },
+                        Err(e) => panic!("write failed: unexpected error: {:?}", e),
+                        _ => {},
+                    };
+                }
+                match writeln!(t, "{msg}") {
+                    Err(e) if e.kind() == io::ErrorKind::BrokenPipe => std::process::exit(1),
+                    Err(e) => panic!("write failed: unexpected error: {:?}", e),
+                    _ => {}
                 }
-                writeln!(t, "{msg}").unwrap();
                 if color.is_some() {
-                    t.reset().unwrap();
+                    match t.reset() {
+                        Err(term::Error::Io(e)) if e.kind() == io::ErrorKind::BrokenPipe => {
+                            std::process::exit(1);
+                        },
+                        Err(e) => panic!("write failed: unexpected error: {:?}", e),
+                        _ => {},
+                    };
                 }
             }
             None => println!("{msg}"),