Add ability to cancel a PR review.

Author: grokys

src/GitHub.App/SampleData/PullRequestReviewAuthoringViewModelDesigner.cs

@@ -48,6 +48,7 @@ public PullRequestReviewAuthoringViewModelDesigner()
         public IPullRequestModel PullRequestModel { get; set; }
         public string RemoteRepositoryOwner { get; set; }
         public ReactiveCommand<Unit> Submit { get; }
+        public ReactiveCommand<Unit> Cancel { get; }
 
         public Task InitializeAsync(
             ILocalRepositoryModel localRepository,

src/GitHub.App/ViewModels/GitHubPane/PullRequestReviewAuthoringViewModel.cs

@@ -58,6 +58,7 @@ public PullRequestReviewAuthoringViewModel(
 
             Files = files;
             Submit = ReactiveCommand.CreateAsyncTask(DoSubmit);
+            Cancel = ReactiveCommand.CreateAsyncTask(DoCancel);
         }
 
         /// <inheritdoc/>
@@ -112,6 +113,7 @@ public IReadOnlyList<IPullRequestReviewFileCommentViewModel> FileComments
 
         public ReactiveCommand<object> NavigateToPullRequest { get; }
         public ReactiveCommand<Unit> Submit { get; }
+        public ReactiveCommand<Unit> Cancel { get; }
 
         public async Task InitializeAsync(
             ILocalRepositoryModel localRepository,
@@ -259,5 +261,29 @@ async Task DoSubmit(object arg)
                 IsBusy = false;
             }
         }
+
+        async Task DoCancel(object arg)
+        {
+            OperationError = null;
+            IsBusy = true;
+
+            try
+            {
+                if (Model?.Id != 0)
+                {
+                    await session.CancelReview();
+                }
+
+                Close();
+            }
+            catch (Exception ex)
+            {
+                OperationError = ex.Message;
+            }
+            finally
+            {
+                IsBusy = false;
+            }
+        }
     }
 }

src/GitHub.Exports.Reactive/Services/IPullRequestSession.cs

@@ -122,6 +122,14 @@ Task<IPullRequestReviewCommentModel> PostReviewComment(
         /// </summary>
         Task<IPullRequestReviewModel> StartReview();
 
+        /// <summary>
+        /// Cancels the currently pending review.
+        /// </summary>
+        /// <exception cref="InvalidOperationException">
+        /// There is no pending review.
+        /// </exception>
+        Task CancelReview();
+
         /// <summary>
         /// Posts the currently pending review.
         /// </summary>

src/GitHub.Exports.Reactive/ViewModels/GitHubPane/IPullRequestReviewAuthoringViewModel.cs

@@ -72,6 +72,11 @@ public interface IPullRequestReviewAuthoringViewModel : IPanePageViewModel, IDis
         /// </summary>
         ReactiveCommand<Unit> Submit { get; }
 
+        /// <summary>
+        /// Gets a command which cancels the review.
+        /// </summary>
+        ReactiveCommand<Unit> Cancel { get; }
+
         /// <summary>
         /// Initializes the view model for creating a new review.
         /// </summary>

src/GitHub.InlineReviews/Services/IPullRequestSessionService.cs

@@ -181,6 +181,14 @@ Task<IPullRequestReviewModel> CreatePendingReview(
             IAccount user,
             string pullRequestId);
 
+        /// <summary>
+        /// Cancels a pending review on the server.
+        /// </summary>
+        /// <param name="reviewId">The GraphQL ID of the review.</param>
+        Task CancelPendingReview(
+            ILocalRepositoryModel localRepository,
+            string reviewId);
+
         /// <summary>
         /// Posts PR review with no comments.
         /// </summary>

src/GitHub.InlineReviews/Services/PullRequestSession.cs

@@ -213,6 +213,26 @@ public async Task<IPullRequestReviewModel> StartReview()
             return model;
         }
 
+        /// <inheritdoc/>
+        public async Task CancelReview()
+        {
+            if (!HasPendingReview)
+            {
+                throw new InvalidOperationException("There is no pending review to cancel.");
+            }
+
+            await service.CancelPendingReview(LocalRepository, pendingReviewNodeId);
+
+            PullRequest.Reviews = PullRequest.Reviews
+                .Where(x => x.NodeId != pendingReviewNodeId)
+                .ToList();
+            PullRequest.ReviewComments = PullRequest.ReviewComments
+                .Where(x => x.PullRequestReviewId != PendingReviewId)
+                .ToList();
+
+            await Update(PullRequest);
+        }
+
         /// <inheritdoc/>
         public async Task<IPullRequestReviewModel> PostReview(string body, Octokit.PullRequestReviewEvent e)
         {

src/GitHub.InlineReviews/Services/PullRequestSessionService.cs

@@ -349,6 +349,26 @@ public async Task<IPullRequestReviewModel> CreatePendingReview(
             return result;
         }
 
+        /// <inheritdoc/>
+        public async Task CancelPendingReview(
+            ILocalRepositoryModel localRepository,
+            string reviewId)
+        {
+            var address = HostAddress.Create(localRepository.CloneUrl.Host);
+            var graphql = await graphqlFactory.CreateConnection(address);
+
+            var delete = new DeletePullRequestReviewInput
+            {
+                PullRequestReviewId = reviewId,
+            };
+
+            var deleteReview = new Mutation()
+                .DeletePullRequestReview(delete)
+                .Select(x => x.ClientMutationId);
+
+            await graphql.Run(deleteReview);
+        }
+
         /// <inheritdoc/>
         public async Task<IPullRequestReviewModel> PostReview(
             ILocalRepositoryModel localRepository,

src/GitHub.VisualStudio/Views/GitHubPane/PullRequestReviewAuthoringView.xaml

@@ -74,7 +74,7 @@
                     </ui:DropDownButton.DropDownContent>
                 </ui:DropDownButton>
                 <Rectangle Fill="{DynamicResource GitHubHeaderSeparatorBrush}" Width="1" Height="16" Margin="4 0"/>
-                <ui:GitHubActionLink VerticalAlignment="Center">Cancel</ui:GitHubActionLink>
+                <ui:GitHubActionLink Command="{Binding Cancel}" VerticalAlignment="Center">Cancel</ui:GitHubActionLink>
             </StackPanel>
 
             <TextBox Grid.Column="0"