Class design changes for GitLabApiTransport

* get and post should return Optionals, as the GsonParserUtil.parseHttpResponse method can return a null.
* replaceClazz is replaced with responseType, which is a Type. This lets us pass in parameterized Types for GSON to case responses to.

BUG=393370224
PiperOrigin-RevId: 726574202
Change-Id: I82694eca30763fe70494e948755207e034d21482

java/com/google/copybara/git/gitlab/api/GitLabApiTransport.java

@@ -20,6 +20,8 @@
 import com.google.copybara.exception.RepoException;
 import com.google.copybara.exception.ValidationException;
 import com.google.copybara.git.gitlab.api.entities.GitLabApiEntity;
+import java.lang.reflect.Type;
+import java.util.Optional;
 
 /** An interface for transports that communicate with a GitLab API endpoint. */
 public interface GitLabApiTransport {
@@ -29,12 +31,13 @@ public interface GitLabApiTransport {
    *
    * @param <T> the class the JSON response will be parsed to
    * @param path the path to call, e.g. projects/13422/merge_requests
+   * @param responseType the Java type that GSON should parse the response into
    * @param headers the headers to add to the HTTP request
-   * @return the returned {@link T}
+   * @return the returned {@link T}, if a response is returned
    * @throws GitLabApiException if there is an issue performing the request
    * @throws ValidationException if there is an issue with credential issuing or retrieval
    */
-  <T> T get(String path, Class<T> responseClazz, ImmutableListMultimap<String, String> headers)
+  <T> Optional<T> get(String path, Type responseType, ImmutableListMultimap<String, String> headers)
       throws GitLabApiException, ValidationException;
 
   /**
@@ -43,14 +46,15 @@ <T> T get(String path, Class<T> responseClazz, ImmutableListMultimap<String, Str
    * @param <T> the class the JSON response will be parsed to
    * @param path the path to call, e.g. projects/13422/merge_requests
    * @param request the object to send as part of the request
-   * @return the returned {@link T}
+   * @param responseType the Java type that GSON should parse the response into
+   * @return the returned {@link T}, if a response is returned
    * @throws GitLabApiException if there is an issue performing the request
    * @throws ValidationException if there is an issue with credential issuing or retrieval
    */
-  <T> T post(
+  <T> Optional<T> post(
       String path,
       GitLabApiEntity request,
-      Class<T> responseClazz,
+      Type responseType,
       ImmutableListMultimap<String, String> headers)
       throws RepoException, ValidationException;
 

java/com/google/copybara/git/gitlab/api/GitLabApiTransportImpl.java

@@ -34,9 +34,10 @@
 import com.google.copybara.http.auth.AuthInterceptor;
 import com.google.copybara.json.GsonParserUtil;
 import com.google.copybara.util.console.Console;
-import com.google.gson.reflect.TypeToken;
 import java.io.IOException;
+import java.lang.reflect.Type;
 import java.net.URI;
+import java.util.Optional;
 import javax.annotation.Nullable;
 
 /**
@@ -64,16 +65,16 @@ public GitLabApiTransportImpl(
   }
 
   @Override
-  public <T> T get(
-      String path, Class<T> responseClazz, ImmutableListMultimap<String, String> headers)
+  public <T> Optional<T> get(
+      String path, Type responseType, ImmutableListMultimap<String, String> headers)
       throws GitLabApiException, ValidationException {
     GenericUrl url = getFullEndpointGenericUrl(path);
     try {
       console.verboseFmt("Sending GET request to %s", url);
       HttpResponse httpResponse = getGetHttpResponse(headers, url);
       // TODO: b/394914756 - Support GitLab API pagination
-      return GsonParserUtil.parseHttpResponse(
-          httpResponse, TypeToken.get(responseClazz).getType(), false);
+      return Optional.ofNullable(
+          GsonParserUtil.parseHttpResponse(httpResponse, responseType, false));
     } catch (HttpResponseException e) {
       throw new GitLabApiException(
           String.format("Error calling GET on %s", url), e.getStatusCode(), e);
@@ -107,19 +108,18 @@ private HttpRequest getHttpRequest(
   }
 
   @Override
-  public <T> T post(
+  public <T> Optional<T> post(
       String path,
       GitLabApiEntity request,
-      Class<T> responseClazz,
+      Type responseType,
       ImmutableListMultimap<String, String> headers)
       throws GitLabApiException, ValidationException {
     GenericUrl url = getFullEndpointGenericUrl(path);
     try {
       console.verboseFmt("Sending POST request to %s", url);
       HttpResponse httpResponse = getPostHttpResponse(request, url);
-      // TODO: b/394914756 - Support GitLab API pagination
-      return GsonParserUtil.parseHttpResponse(
-          httpResponse, TypeToken.get(responseClazz).getType(), false);
+      return Optional.ofNullable(
+          GsonParserUtil.parseHttpResponse(httpResponse, responseType, false));
     } catch (HttpResponseException e) {
       throw new GitLabApiException(
           String.format("Error calling POST on %s", url), e.getStatusCode(), e);

javatests/com/google/copybara/git/gitlab/api/GitLabApiTransportImplTest.java

@@ -47,6 +47,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -75,12 +76,13 @@ public void testSimpleGetRequest() throws Exception {
             "https://gitlab.copybara.io/capybara/project",
             bearerInterceptor);
 
-    TestResponse testResponse =
+    Optional<TestResponse> testResponse =
         underTest.get(
             "/projects/12345/test_request", TestResponse.class, ImmutableListMultimap.of());
 
-    assertThat(testResponse.getId()).isEqualTo(12345);
-    assertThat(testResponse.getDescription()).isEqualTo("capybara");
+    assertThat(testResponse).isPresent();
+    assertThat(testResponse.get().getId()).isEqualTo(12345);
+    assertThat(testResponse.get().getDescription()).isEqualTo("capybara");
   }
 
   @Test
@@ -95,7 +97,7 @@ public void testSimpleGetRequest_withHttpPort() throws Exception {
             "https://gitlab.copybara.io:8080/capybara/project",
             bearerInterceptor);
 
-    TestResponse unused =
+    Optional<TestResponse> unused =
         underTest.get(
             "/projects/12345/test_request", TestResponse.class, ImmutableListMultimap.of());
 
@@ -149,15 +151,16 @@ public void testSimplePostRequest() throws Exception {
             bearerInterceptor);
     TestRequest testRequest = new TestRequest(54321, "baracopy");
 
-    TestResponse testResponse =
+    Optional<TestResponse> testResponse =
         underTest.post(
             "/projects/12345/test_request",
             testRequest,
             TestResponse.class,
             ImmutableListMultimap.of());
 
-    assertThat(testResponse.getId()).isEqualTo(12345);
-    assertThat(testResponse.getDescription()).isEqualTo("capybara");
+    assertThat(testResponse).isPresent();
+    assertThat(testResponse.get().getId()).isEqualTo(12345);
+    assertThat(testResponse.get().getDescription()).isEqualTo("capybara");
   }
 
   @Test
@@ -173,7 +176,7 @@ public void testSimplePostRequest_httpPort() throws Exception {
             bearerInterceptor);
     TestRequest testRequest = new TestRequest(54321, "baracopy");
 
-    TestResponse unused =
+    Optional<TestResponse> unused =
         underTest.post(
             "/projects/12345/test_request",
             testRequest,
@@ -244,7 +247,7 @@ public void testSetPasswordHeaders() throws Exception {
         getApiTransport(
             httpTransport, "https://gitlab.copybara.io/capybara/project", bearerInterceptor);
 
-    TestResponse unused =
+    Optional<TestResponse> unused =
         underTest.get(
             "/projects/12345/test_request", TestResponse.class, ImmutableListMultimap.of());