Fix draft appearing after sucessful submit.

In certain situations, the inline comment thread was refreshed before the `DeleteDraft(comment)` line in `PullRequestReviewCommentThreadViewModel.PostComment` was run, meaning that the draft would be displayed _after_ the comment was succesfully submitted.

Work around this by deleting the draft before submitting the comment, and if we get an error re-insert the draft.

Author: grokys

src/GitHub.App/ViewModels/PullRequestReviewCommentThreadViewModel.cs

@@ -161,35 +161,43 @@ public override async Task PostComment(ICommentViewModel comment)
         {
             Guard.ArgumentNotNull(comment, nameof(comment));
 
-            if (IsNewThread)
+            await DeleteDraft(comment).ConfigureAwait(false);
+
+            try
             {
-                var diffPosition = File.Diff
-                    .SelectMany(x => x.Lines)
-                    .FirstOrDefault(x =>
+                if (IsNewThread)
+                {
+                    var diffPosition = File.Diff
+                        .SelectMany(x => x.Lines)
+                        .FirstOrDefault(x =>
+                        {
+                            var line = Side == DiffSide.Left ? x.OldLineNumber : x.NewLineNumber;
+                            return line == LineNumber + 1;
+                        });
+
+                    if (diffPosition == null)
                     {
-                        var line = Side == DiffSide.Left ? x.OldLineNumber : x.NewLineNumber;
-                        return line == LineNumber + 1;
-                    });
-
-                if (diffPosition == null)
+                        throw new InvalidOperationException("Unable to locate line in diff.");
+                    }
+
+                    await Session.PostReviewComment(
+                        comment.Body,
+                        File.CommitSha,
+                        File.RelativePath.Replace("\\", "/"),
+                        File.Diff,
+                        diffPosition.DiffLineNumber).ConfigureAwait(false);
+                }
+                else
                 {
-                    throw new InvalidOperationException("Unable to locate line in diff.");
+                    var replyId = Comments[0].Id;
+                    await Session.PostReviewComment(comment.Body, replyId).ConfigureAwait(false);
                 }
-
-                await Session.PostReviewComment(
-                    comment.Body,
-                    File.CommitSha,
-                    File.RelativePath.Replace("\\", "/"),
-                    File.Diff,
-                    diffPosition.DiffLineNumber).ConfigureAwait(false);
             }
-            else
+            catch
             {
-                var replyId = Comments[0].Id;
-                await Session.PostReviewComment(comment.Body, replyId).ConfigureAwait(false);
+                UpdateDraft(comment).Forget();
+                throw;
             }
-
-            await DeleteDraft(comment).ConfigureAwait(false);
         }
 
         public override async Task EditComment(ICommentViewModel comment)
@@ -235,5 +243,12 @@ protected override (string key, string secondaryKey) GetDraftKeys(ICommentViewMo
                 File.RelativePath,
                 LineNumber);
         }
+        
+        async Task UpdateDraft(ICommentViewModel comment)
+        {
+            var draft = BuildDraft(comment);
+            var (key, secondaryKey) = GetDraftKeys(comment);
+            await DraftStore.UpdateDraft(key, secondaryKey, draft).ConfigureAwait(true);
+        }
     }
 }