Only show the progress bar after printing stdout/stderr if the printi…

…ng cleared the progress bar.

I'm not sure how to add a test for this because the fancy terminal overwriting the ui does isn't really compatible with our test infrastructure for assertions on blaze output. Will keep on trying, but wanted to fix the bug first.

PiperOrigin-RevId: 344144890

src/main/java/com/google/devtools/build/lib/runtime/UiEventHandler.java

@@ -303,8 +303,9 @@ private void handleLocked(Event event, @Nullable byte[] stdout, @Nullable byte[]
             stream.write(event.getMessageBytes());
             stream.flush();
           } else {
-            writeToStream(stream, event.getKind(), event.getMessageBytes());
-            if (showProgress && cursorControl) {
+            boolean clearedProgress =
+                writeToStream(stream, event.getKind(), event.getMessageBytes());
+            if (clearedProgress && showProgress && cursorControl) {
               addProgressBar();
             }
             terminal.flush();
@@ -452,14 +453,14 @@ public void handle(Event event) {
     handleInternal(event);
   }
 
-  private void writeToStream(OutputStream stream, EventKind eventKind, byte[] message)
+  private boolean writeToStream(OutputStream stream, EventKind eventKind, byte[] message)
       throws IOException {
     int eolIndex = Bytes.lastIndexOf(message, (byte) '\n');
     ByteArrayOutputStream outLineBuffer =
         eventKind == EventKind.STDOUT ? stdoutLineBuffer : stderrLineBuffer;
     if (eolIndex < 0) {
       outLineBuffer.write(message);
-      return;
+      return false;
     }
 
     clearProgressBar();
@@ -473,6 +474,7 @@ private void writeToStream(OutputStream stream, EventKind eventKind, byte[] mess
     stream.flush();
 
     outLineBuffer.write(message, eolIndex + 1, message.length - eolIndex - 1);
+    return true;
   }
 
   private void setEventKindColor(EventKind kind) throws IOException {