Do not add Upgrade header if Connection header already present (the caller manually manages connection state)

Author: ok2c

httpclient5/src/main/java/org/apache/hc/client5/http/protocol/RequestUpgrade.java

@@ -67,7 +67,9 @@ public void process(
         final RequestConfig requestConfig = clientContext.getRequestConfigOrDefault();
         if (requestConfig.isProtocolUpgradeEnabled()) {
             final ProtocolVersion version = request.getVersion() != null ? request.getVersion() : clientContext.getProtocolVersion();
-            if (!request.containsHeader(HttpHeaders.UPGRADE) && version.getMajor() == 1 && version.getMinor() >= 1) {
+            if (!request.containsHeader(HttpHeaders.UPGRADE) &&
+                    !request.containsHeader(HttpHeaders.CONNECTION) &&
+                    version.getMajor() == 1 && version.getMinor() >= 1) {
                 if (LOG.isDebugEnabled()) {
                     LOG.debug("Connection is upgradable: protocol version = {}", version);
                 }

httpclient5/src/test/java/org/apache/hc/client5/http/protocol/TestRequestUpgrade.java

@@ -109,6 +109,14 @@ void testDoUpgradeIfAlreadyTLS() throws Exception {
         Assertions.assertFalse(get.containsHeader(HttpHeaders.UPGRADE));
     }
 
+    @Test
+    void testDoUpgradeIfConnectionHeaderPresent() throws Exception {
+        final HttpRequest get = new BasicHttpRequest("GET", "/");
+        get.addHeader(HttpHeaders.CONNECTION, "keep-alive");
+        interceptor.process(get, null, context);
+        Assertions.assertFalse(get.containsHeader(HttpHeaders.UPGRADE));
+    }
+
     @Test
     void testDoUpgradeNonSafeMethodsOrTrace() throws Exception {
         final HttpRequest post = new BasicHttpRequest("POST", "/");