HTTP/1.1: Suppress Content-Length for 1xx responses

httpcore5/src/main/java/org/apache/hc/core5/http/protocol/ResponseContent.java

@@ -122,7 +122,7 @@ public void process(final HttpResponse response, final EntityDetails entity, fin
             MessageSupport.addContentEncodingHeader(response, entity);
         } else {
             final int status = response.getCode();
-            if (status != HttpStatus.SC_NO_CONTENT && status != HttpStatus.SC_NOT_MODIFIED) {
+            if (status >= 200 && status != HttpStatus.SC_NO_CONTENT && status != HttpStatus.SC_NOT_MODIFIED) {
                 response.addHeader(HttpHeaders.CONTENT_LENGTH, "0");
             }
         }

httpcore5/src/test/java/org/apache/hc/core5/http/protocol/TestResponseContent.java

@@ -0,0 +1,84 @@
+/*
+ * ====================================================================
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ *
+ */
+
+package org.apache.hc.core5.http.protocol;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import org.apache.hc.core5.http.HttpHeaders;
+import org.apache.hc.core5.http.HttpStatus;
+import org.apache.hc.core5.http.HttpVersion;
+import org.apache.hc.core5.http.message.BasicHttpResponse;
+import org.junit.jupiter.api.Test;
+
+class TestResponseContent {
+
+    @Test
+    void testNoContentLengthForInformationalResponses() throws Exception {
+        final ResponseContent interceptor = new ResponseContent();
+        final HttpCoreContext context = HttpCoreContext.create();
+        context.setProtocolVersion(HttpVersion.HTTP_1_1);
+
+        for (int status = 100; status < 200; status++) {
+            final BasicHttpResponse response = new BasicHttpResponse(status);
+            interceptor.process(response, null, context);
+
+            assertFalse(response.containsHeader(HttpHeaders.CONTENT_LENGTH),
+                    "Unexpected Content-Length for status " + status);
+        }
+    }
+
+    @Test
+    void testContentLengthZeroForOkResponseWithoutEntity() throws Exception {
+        final ResponseContent interceptor = new ResponseContent();
+        final HttpCoreContext context = HttpCoreContext.create();
+        context.setProtocolVersion(HttpVersion.HTTP_1_1);
+
+        final BasicHttpResponse response = new BasicHttpResponse(HttpStatus.SC_OK);
+        interceptor.process(response, null, context);
+
+        assertNotNull(response.getFirstHeader(HttpHeaders.CONTENT_LENGTH));
+        assertEquals("0", response.getFirstHeader(HttpHeaders.CONTENT_LENGTH).getValue());
+    }
+
+    @Test
+    void testNoContentLengthForNoContentAndNotModified() throws Exception {
+        final ResponseContent interceptor = new ResponseContent();
+        final HttpCoreContext context = HttpCoreContext.create();
+        context.setProtocolVersion(HttpVersion.HTTP_1_1);
+
+        final BasicHttpResponse r204 = new BasicHttpResponse(HttpStatus.SC_NO_CONTENT);
+        interceptor.process(r204, null, context);
+        assertFalse(r204.containsHeader(HttpHeaders.CONTENT_LENGTH));
+
+        final BasicHttpResponse r304 = new BasicHttpResponse(HttpStatus.SC_NOT_MODIFIED);
+        interceptor.process(r304, null, context);
+        assertFalse(r304.containsHeader(HttpHeaders.CONTENT_LENGTH));
+    }
+}