mid work

Author: iliapolo

packages/@jsii/java-runtime/project/src/main/java/software/amazon/jsii/JsiiRuntime.java

@@ -516,7 +516,10 @@ private void acceptData(final boolean uninterruptible) throws IOException {
                     this.buffer.write(read);
                 }
                 if (read == '\n' || this.eof) {
-                    processLine(new String(buffer.toByteArray(), StandardCharsets.UTF_8));
+                    // don't print an empty line if we're at the end of the file and the buffer is empty.
+                    if (!this.eof || buffer.size() > 0) {
+                        processLine(new String(buffer.toByteArray(), StandardCharsets.UTF_8));
+                    }
                     buffer.reset();
                 }
             }
@@ -526,6 +529,13 @@ private void processLine(final String line) {
             try {
                 final JsonNode tree = objectMapper.readTree(line);
                 final ConsoleOutput consoleOutput = objectMapper.treeToValue(tree, ConsoleOutput.class);
+                if (consoleOutput == null) {
+                    // null means the line was empty, but the above objectMapper calls will return null
+                    // We would throw JsonProcessingException to avoid duplication, but the constructors
+                    // are protected, and the subclasses need too much information
+                    System.err.println(line);
+                    return;
+                }
                 if (consoleOutput.stderr != null) {
                     System.err.write(consoleOutput.stderr, 0, consoleOutput.stderr.length);
                 }

packages/@jsii/java-runtime/project/src/test/java/software/amazon/jsii/JsiiRuntimeTest.java

@@ -9,6 +9,29 @@
 import java.util.Collections;
 
 public final class JsiiRuntimeTest {
+
+    @Test
+    public void errorSteamSinkDoesntCrash() {
+
+        ByteArrayOutputStream err = new ByteArrayOutputStream();
+        PrintStream originalErr = System.err;
+
+        // to capture writes to System.err, which happen when the error stream
+        // sink crashes. kind of a silly...but simple, and works.
+        System.setErr(new PrintStream(err));
+
+        try {
+            final JsiiRuntime runtime = new JsiiRuntime(null, null);
+            runtime.getClient().createObject("Object", Collections.emptyList(), Collections.emptyList(),
+                    Collections.emptyList());
+            runtime.terminate();
+            Assertions.assertFalse(err.toString().contains(
+                    "Unexpected error in background thread \"software.amazon.jsii.JsiiRuntime.ErrorStreamSink\""));
+        } finally {
+            System.setErr(originalErr);
+        }
+    }
+
     @Test
     public void withNoCustomization() {
         final JsiiRuntime runtime = new JsiiRuntime(null, null);