Make sure to discard a draft whenever we're saving. Release-Notes: fixes deletion of patchset comment right before saving. Google-Bug-Id: b/309970044, b/309533366 Change-Id: I420fd0193f4911aca85b26989ebfa60f784f90d7

diff --git a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
index 7a8779d..459ff0f 100644
--- a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
+++ b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts

@@ -1452,13 +1452,19 @@
     await this.save();
   }
 
-  convertToCommentInput(): CommentInput | undefined {
+  async convertToCommentInputAndOrDiscard(): Promise<CommentInput | undefined> {
     if (!this.somethingToSave() || !this.comment) return;
-    return convertToCommentInput({
-      ...this.comment,
-      message: this.messageText.trimEnd(),
-      unresolved: this.unresolved,
-    });
+    const messageToSave = this.messageText.trimEnd();
+    if (messageToSave === '') {
+      await this.getCommentsModel().discardDraft(id(this.comment));
+      return undefined;
+    } else {
+      return convertToCommentInput({
+        ...this.comment,
+        message: this.messageText.trimEnd(),
+        unresolved: this.unresolved,
+      });
+    }
   }
 
   async save() {

diff --git a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment_test.ts b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment_test.ts
index a01d3a4..03d8e32 100644
--- a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment_test.ts
+++ b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment_test.ts

@@ -734,6 +734,21 @@
       assert.isFalse(saveStub.called);
     });
 
+    test('converting to input for empty text calls discard()', async () => {
+      const saveStub = sinon.stub(commentsModel, 'saveDraft');
+      const discardStub = sinon.stub(commentsModel, 'discardDraft');
+      element.comment = createDraft();
+      element.editing = true;
+      await element.updateComplete;
+
+      element.messageText = '';
+      await element.updateComplete;
+
+      await element.convertToCommentInputAndOrDiscard();
+      assert.isTrue(discardStub.called);
+      assert.isFalse(saveStub.called);
+    });
+
     test('handlePleaseFix fires reply-to-comment event', async () => {
       const listener = listenOnce<ReplyToCommentEvent>(
         element,