Revert "testing: delete deprecated StreamRecorder" (#3801)

This reverts commit dc71083ce9.

StreamRecorder is too old and may have users unable to migrate it out easily soon.

testing/src/main/java/io/grpc/testing/StreamRecorder.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2014, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.testing;
+
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.SettableFuture;
+import io.grpc.ExperimentalApi;
+import io.grpc.stub.StreamObserver;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import javax.annotation.Nullable;
+
+/**
+ * Utility implementation of {@link StreamObserver} used in testing. Records all the observed
+ * values produced by the stream as well as any errors.
+ *
+ * @deprecated Not for public use
+ */
+@Deprecated
+@ExperimentalApi("https://github.com/grpc/grpc-java/issues/1791")
+public class StreamRecorder<T> implements StreamObserver<T> {
+
+  /**
+   * Creates a new recorder.
+   */
+  public static <T> StreamRecorder<T> create() {
+    return new StreamRecorder<T>();
+  }
+
+  private final CountDownLatch latch;
+  private final List<T> results;
+  private Throwable error;
+  private final SettableFuture<T> firstValue;
+
+  private StreamRecorder() {
+    firstValue = SettableFuture.create();
+    latch = new CountDownLatch(1);
+    results = Collections.synchronizedList(new ArrayList<T>());
+  }
+
+  @Override
+  public void onNext(T value) {
+    if (!firstValue.isDone()) {
+      firstValue.set(value);
+    }
+    results.add(value);
+  }
+
+  @Override
+  public void onError(Throwable t) {
+    if (!firstValue.isDone()) {
+      firstValue.setException(t);
+    }
+    error = t;
+    latch.countDown();
+  }
+
+  @Override
+  public void onCompleted() {
+    if (!firstValue.isDone()) {
+      firstValue.setException(new IllegalStateException("No first value provided"));
+    }
+    latch.countDown();
+  }
+
+  /**
+   * Waits for the stream to terminate.
+   */
+  public void awaitCompletion() throws Exception {
+    latch.await();
+  }
+
+  /**
+   * Waits a fixed timeout for the stream to terminate.
+   */
+  public boolean awaitCompletion(int timeout, TimeUnit unit) throws Exception {
+    return latch.await(timeout, unit);
+  }
+
+  /**
+   * Returns the current set of received values.
+   */
+  public List<T> getValues() {
+    return Collections.unmodifiableList(results);
+  }
+
+  /**
+   * Returns the stream terminating error.
+   */
+  @Nullable public Throwable getError() {
+    return error;
+  }
+
+  /**
+   * Returns a {@link ListenableFuture} for the first value received from the stream. Useful
+   * for testing unary call patterns.
+   */
+  public ListenableFuture<T> firstValue() {
+    return firstValue;
+  }
+}