fix: update NetHttpRequest to prevent silent retry of DELETE requests (googleapis#1472)

HttpURLConnection will silently retry `DELETE` requests.

This behavior is similar to other existing JDK bugs (JDK-6382788[1], JDK-6427251[2]).

google-http-java-client already contains a workaround for POST and PUT requests NetHttpRequest.java#L108-L112, but does not account for `DELETE` with an empty body. This change adds handling for DELETE to leverage the same workaround as POST and PUT.

[1] https://bugs.java.com/bugdatabase/view_bug.do?bug_id=6382788
[2] https://bugs.java.com/bugdatabase/view_bug.do?bug_id=6427251

Fixes googleapis#1471

Author: BenWhitehead

google-http-client/src/main/java/com/google/api/client/http/javanet/NetHttpRequest.java

@@ -141,6 +141,9 @@ LowLevelHttpResponse execute(final OutputWriter outputWriter) throws IOException
         Preconditions.checkArgument(
             contentLength == 0, "%s with non-zero content length is not supported", requestMethod);
       }
+    } else if ("DELETE".equals(connection.getRequestMethod())) {
+      connection.setDoOutput(true);
+      connection.setFixedLengthStreamingMode(0L);
     }
     // connect
     boolean successfulConnection = false;

google-http-client/src/main/java/com/google/api/client/testing/http/javanet/MockHttpURLConnection.java

@@ -42,6 +42,10 @@ public class MockHttpURLConnection extends HttpURLConnection {
 
   /** Whether {@link #doOutput} was called. */
   private boolean doOutputCalled;
+  /** Whether {@link #setFixedLengthStreamingMode(int)} was called. */
+  private boolean setFixedLengthStreamingModeIntCalled = false;
+  /** Whether {@link #setFixedLengthStreamingMode(long)} was called. */
+  private boolean setFixedLengthStreamingModeLongCalled = false;
 
   /**
    * Output stream or {@code null} to throw an {@link UnknownServiceException} when {@link
@@ -205,4 +209,24 @@ public String getHeaderField(String name) {
   public int getChunkLength() {
     return chunkLength;
   }
+
+  @Override
+  public void setFixedLengthStreamingMode(int contentLength) {
+    this.setFixedLengthStreamingModeIntCalled = true;
+    super.setFixedLengthStreamingMode(contentLength);
+  }
+
+  @Override
+  public void setFixedLengthStreamingMode(long contentLength) {
+    this.setFixedLengthStreamingModeLongCalled = true;
+    super.setFixedLengthStreamingMode(contentLength);
+  }
+
+  public boolean isSetFixedLengthStreamingModeIntCalled() {
+    return setFixedLengthStreamingModeIntCalled;
+  }
+
+  public boolean isSetFixedLengthStreamingModeLongCalled() {
+    return setFixedLengthStreamingModeLongCalled;
+  }
 }

google-http-client/src/test/java/com/google/api/client/http/javanet/NetHttpRequestTest.java

@@ -233,4 +233,17 @@ public void testChunkedLengthNotSet() throws Exception {
     assertEquals(connection.getChunkLength(), -1);
     assertEquals("6", request.getRequestProperty("Content-Length"));
   }
+
+  // see https://github.com/googleapis/google-http-java-client/issues/1471 for more details
+  @Test
+  public void testDeleteSetsContentLengthToZeroWithoutContent() throws Exception {
+    MockHttpURLConnection connection = new MockHttpURLConnection(new URL(HttpTesting.SIMPLE_URL));
+    connection.setRequestMethod("DELETE");
+    NetHttpRequest request = new NetHttpRequest(connection);
+    request.execute();
+
+    assertTrue(connection.doOutputCalled());
+    assertTrue(connection.isSetFixedLengthStreamingModeLongCalled());
+    assertFalse(connection.isSetFixedLengthStreamingModeIntCalled());
+  }
 }