DiscussionApi: Retrieve a single discussion from a Merge Request (#1284)

---------

Co-authored-by: Jeremie Bresson <jmini@jmini.fr>

Author: lucasls

gitlab4j-api/src/main/java/org/gitlab4j/api/DiscussionsApi.java

@@ -361,6 +361,50 @@ public Stream<Discussion> getMergeRequestDiscussionsStream(Object projectIdOrPat
         return (pager.stream());
     }
 
+    /**
+     * Get a single discussion for the specified merge request.
+     *
+     * <pre><code>GitLab Endpoint: GET /projects/:id/merge_requests/:merge_request_iid/discussions/:discussion_id</code></pre>
+     *
+     * @param projectIdOrPath projectIdOrPath the project in the form of an Long(ID), String(path), or Project instance
+     * @param mergeRequestIid the internal ID of the merge request
+     * @param discussionId the ID of the discussion
+     * @return the Discussion instance specified by discussionId for the specified  merge request
+     * @throws GitLabApiException if any exception occurs during execution
+     */
+    public Discussion getMergeRequestDiscussion(Object projectIdOrPath, Long mergeRequestIid, String discussionId)
+            throws GitLabApiException {
+        Response response = get(
+                Response.Status.OK,
+                null,
+                "projects",
+                getProjectIdOrPath(projectIdOrPath),
+                "merge_requests",
+                mergeRequestIid,
+                "discussions",
+                discussionId);
+        return (response.readEntity(Discussion.class));
+    }
+
+    /**
+     * Get an Optional instance of a single discussion for the specified merge request.
+     *
+     * <pre><code>GitLab Endpoint: GET /projects/:id/merge_requests/:merge_request_iid/discussions/:discussion_id</code></pre>
+     *
+     * @param projectIdOrPath projectIdOrPath the project in the form of an Long(ID), String(path), or Project instance
+     * @param mergeRequestIid the internal ID of the merge request
+     * @param discussionId the ID of the discussion
+     * @return an Optional instance with the specified Discussion instance as a value
+     */
+    public Optional<Discussion> getOptionalMergeRequestDiscussion(
+            Object projectIdOrPath, Long mergeRequestIid, String discussionId) throws GitLabApiException {
+        try {
+            return (Optional.ofNullable(getMergeRequestDiscussion(projectIdOrPath, mergeRequestIid, discussionId)));
+        } catch (GitLabApiException glae) {
+            return (GitLabApi.createOptionalFromException(glae));
+        }
+    }
+
     /**
      * Creates a new discussion to a single project merge request. This is similar to creating
      * a note but other comments (replies) can be added to it later.

gitlab4j-api/src/test/java/org/gitlab4j/api/TestMergeRequestDiscussionsApi.java

@@ -8,6 +8,7 @@
 import static org.mockito.MockitoAnnotations.openMocks;
 
 import java.util.List;
+import java.util.Optional;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -38,7 +39,8 @@ public class TestMergeRequestDiscussionsApi implements Constants {
     @BeforeEach
     public void setUp() throws Exception {
         openMocks(this);
-        response = new MockResponse(Discussion.class, null, "merge-request-discussions.json");
+        response =
+                new MockResponse(Discussion.class, "merge-request-discussion.json", "merge-request-discussions.json");
         when(gitLabApi.getApiClient()).thenReturn(gitLabApiClient);
         when(gitLabApiClient.validateSecretToken(any())).thenReturn(true);
         when(gitLabApiClient.get(attributeCaptor.capture(), Mockito.any(Object[].class)))
@@ -73,4 +75,18 @@ public void testGetMergeRequestDiscussionsByStream() throws Exception {
         List<Discussion> discussions = stream.collect(Collectors.toList());
         assertTrue(compareJson(discussions, "merge-request-discussions.json"));
     }
+
+    @Test
+    public void testGetMergeRequestDiscussion() throws Exception {
+        Discussion discussion = new DiscussionsApi(gitLabApi).getMergeRequestDiscussion(1L, 1L, "1");
+        assertNotNull(discussion);
+        assertTrue(compareJson(discussion, "merge-request-discussion.json"));
+    }
+
+    @Test
+    public void testGetOptionalMergeRequestDiscussion() throws Exception {
+        Optional<Discussion> discussion = new DiscussionsApi(gitLabApi).getOptionalMergeRequestDiscussion(1L, 1L, "");
+        assertTrue(discussion.isPresent());
+        assertTrue(compareJson(discussion.get(), "merge-request-discussion.json"));
+    }
 }

gitlab4j-api/src/test/resources/org/gitlab4j/api/merge-request-discussion.json

@@ -0,0 +1,45 @@
+{
+  "id": "6a9c1750b37d513a43987b574953fceb50b03ce7",
+  "individual_note": false,
+  "notes": [
+    {
+      "id": 1126,
+      "type": "DiscussionNote",
+      "author": {
+        "id": 1,
+        "name": "root",
+        "username": "root",
+        "state": "active",
+        "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+        "web_url": "http://localhost:3000/root"
+      },
+      "created_at": "2018-03-03T21:54:39.668Z",
+      "updated_at": "2018-03-03T21:54:39.668Z",
+      "system": false,
+      "noteable_id": 3,
+      "noteable_type": "Merge request",
+      "resolved": false,
+      "resolvable": true
+    },
+    {
+      "id": 1129,
+      "type": "DiscussionNote",
+      "body": "reply to the discussion",
+      "author": {
+        "id": 1,
+        "name": "root",
+        "username": "root",
+        "state": "active",
+        "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+        "web_url": "http://localhost:3000/root"
+      },
+      "created_at": "2018-03-04T13:38:02.127Z",
+      "updated_at": "2018-03-04T13:38:02.127Z",
+      "system": false,
+      "noteable_id": 3,
+      "noteable_type": "Merge request",
+      "resolved": false,
+      "resolvable": true
+    }
+  ]
+}