fix: Handle null server address (#12184)

In case of an invalid endpoint such as `localhost:-1`, the current
parsing logic returns null for server address. This PR made server
address nullable. And added a null check for the port parsing.

In addition, added a try catch for the whole parsing logic because
serviceAddress and serverPort should only be used for obersevability and
should not affect regular requests.

Author: blakeli0

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/rpc/EndpointContext.java

@@ -134,6 +134,7 @@ public static EndpointContext getDefaultInstance() {
 
   public abstract String resolvedEndpoint();
 
+  @Nullable
   public abstract String resolvedServerAddress();
 
   @Nullable
@@ -410,7 +411,7 @@ private Integer parseServerPort(String endpoint) {
         return null;
       }
       HostAndPort hostAndPort = parseServerHostAndPort(endpoint);
-      if (!hostAndPort.hasPort()) {
+      if (hostAndPort == null || !hostAndPort.hasPort()) {
         return null;
       }
       return hostAndPort.getPort();
@@ -466,8 +467,13 @@ public EndpointContext build() throws IOException {
       setResolvedUniverseDomain(determineUniverseDomain());
       String endpoint = determineEndpoint();
       setResolvedEndpoint(endpoint);
-      setResolvedServerAddress(parseServerAddress(resolvedEndpoint()));
-      setResolvedServerPort(parseServerPort(resolvedEndpoint()));
+      try {
+        setResolvedServerAddress(parseServerAddress(resolvedEndpoint()));
+        setResolvedServerPort(parseServerPort(resolvedEndpoint()));
+      } catch (Exception throwable) {
+        // Server address and server port are only used for observability.
+        // We should ignore any errors parsing them and not affect the main client requests.
+      }
       setUseS2A(shouldUseS2A());
       return autoBuild();
     }

sdk-platform-java/gax-java/gax/src/test/java/com/google/api/gax/rpc/EndpointContextTest.java

@@ -683,4 +683,19 @@ void endpointContextBuild_resolvesPort() throws IOException {
             .build();
     Truth.assertThat(endpointContext.resolvedServerPort()).isNull();
   }
+
+  @Test
+  void endpointContextBuild_resolvesInvalidEndpointAndPort() throws Exception {
+
+    String endpoint = "localhost:-1";
+
+    EndpointContext endpointContext =
+        defaultEndpointContextBuilder
+            .setClientSettingsEndpoint(endpoint)
+            .setTransportChannelProviderEndpoint(null)
+            .build();
+
+    Truth.assertThat(endpointContext.resolvedServerAddress()).isNull();
+    Truth.assertThat(endpointContext.resolvedServerPort()).isNull();
+  }
 }