Ensure diagnostics are printed in the correct order

Even when buffered. Ideally we would flush only when the emitter is
done, but that requires larger changes. This gives most of the benefit
of buffering in any case.

diff --git a/src/librustc_errors/json.rs b/src/librustc_errors/json.rs
index f0cfd815a2c3e473f1e127ac08f322745eae39cf..97b9ca924bb7c9460bf4c6703776c8fdf9eca33d 100644 (file)
--- a/src/librustc_errors/json.rs
+++ b/src/librustc_errors/json.rs
@@ -104,7 +104,8 @@ fn emit_diagnostic(&mut self, diag: &crate::Diagnostic) {
             writeln!(&mut self.dst, "{}", as_pretty_json(&data))
         } else {
             writeln!(&mut self.dst, "{}", as_json(&data))
-        };
+        }
+        .and_then(|_| self.dst.flush());
         if let Err(e) = result {
             panic!("failed to print diagnostics: {:?}", e);
         }
@@ -116,7 +117,8 @@ fn emit_artifact_notification(&mut self, path: &Path, artifact_type: &str) {
             writeln!(&mut self.dst, "{}", as_pretty_json(&data))
         } else {
             writeln!(&mut self.dst, "{}", as_json(&data))
-        };
+        }
+        .and_then(|_| self.dst.flush());
         if let Err(e) = result {
             panic!("failed to print notification: {:?}", e);
         }