Fix URI concat issue with HttpClientProtocol

Author: mtdowling

client/client-http/src/main/java/software/amazon/smithy/java/client/http/HttpClientProtocol.java

@@ -54,7 +54,7 @@ public HttpRequest setServiceEndpoint(HttpRequest request, Endpoint endpoint) {
         // If a path is set on the service endpoint, concatenate it with the path of the request.
         if (uri.getRawPath() != null && !uri.getRawPath().isEmpty()) {
             builder.path(uri.getRawPath());
-            builder.concatPath(request.uri().getPath());
+            builder.concatPath(request.uri().getRawPath());
         }
 
         var requestBuilder = request.toBuilder();

client/client-http/src/test/java/software/amazon/smithy/java/client/http/HttpClientProtocolTest.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.java.client.http;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+
+import java.net.URI;
+import java.util.concurrent.CompletableFuture;
+import org.junit.jupiter.api.Test;
+import software.amazon.smithy.java.client.core.endpoint.Endpoint;
+import software.amazon.smithy.java.context.Context;
+import software.amazon.smithy.java.core.schema.ApiOperation;
+import software.amazon.smithy.java.core.schema.SerializableStruct;
+import software.amazon.smithy.java.core.serde.Codec;
+import software.amazon.smithy.java.core.serde.TypeRegistry;
+import software.amazon.smithy.java.http.api.HttpRequest;
+import software.amazon.smithy.java.http.api.HttpResponse;
+import software.amazon.smithy.model.shapes.ShapeId;
+
+public class HttpClientProtocolTest {
+    @Test
+    public void mergesPaths() throws Exception {
+        var hcp = new HttpClientProtocol(ShapeId.from("foo#Bar")) {
+            @Override
+            public Codec payloadCodec() {
+                return null;
+            }
+
+            @Override
+            public <I extends SerializableStruct, O extends SerializableStruct> HttpRequest createRequest(
+                    ApiOperation<I, O> operation,
+                    I input,
+                    Context context,
+                    URI endpoint
+            ) {
+                return null;
+            }
+
+            @Override
+            public <I extends SerializableStruct,
+                    O extends SerializableStruct> CompletableFuture<O> deserializeResponse(
+                            ApiOperation<I, O> operation,
+                            Context context,
+                            TypeRegistry errorRegistry,
+                            HttpRequest request,
+                            HttpResponse response
+                    ) {
+                return null;
+            }
+        };
+
+        var endpoint = Endpoint.builder().uri("https://example.com/foo%20/bar").build();
+        var request = HttpRequest.builder()
+                .method("GET")
+                .uri(new URI("/bam%20"))
+                .build();
+        var merged = hcp.setServiceEndpoint(request, endpoint);
+
+        // It concats the endpoints and maintains percent encoding.
+        assertThat(merged.uri().toString(), equalTo("https://example.com/foo%20/bar/bam%20"));
+    }
+}