Fix detail comments after live updates (#92)

Co-authored-by: gprocunier <gprocunier@users.noreply.github.com>

Author: gprocunier

app/data/subscription-issue-store.js

@@ -4,6 +4,14 @@
 import { debug } from '../utils/logging.js';
 import { cmpPriorityThenCreated } from './sort.js';
 
+/**
+ * @param {object} obj
+ * @param {string} key
+ */
+function hasOwn(obj, key) {
+  return Object.prototype.hasOwnProperty.call(obj, key);
+}
+
 /**
  * Per-subscription issue store. Holds full Issue objects and exposes a
  * deterministic, read-only snapshot for rendering. Applies snapshot/upsert/
@@ -98,6 +106,12 @@ export function createSubscriptionIssueStore(id, options = {}) {
             ? /** @type {number} */ (it.updated_at)
             : 0;
           if (prev_ts <= next_ts) {
+            const has_incoming_comments = hasOwn(it, 'comments');
+            const preserve_comments =
+              !has_incoming_comments && hasOwn(existing, 'comments');
+            const previous_comments = preserve_comments
+              ? existing.comments
+              : undefined;
             // Mutate existing object to preserve reference
             for (const k of Object.keys(existing)) {
               if (!(k in it)) {
@@ -109,6 +123,9 @@ export function createSubscriptionIssueStore(id, options = {}) {
               // @ts-ignore - dynamic assignment
               existing[k] = v;
             }
+            if (preserve_comments) {
+              existing.comments = previous_comments;
+            }
           } else {
             // stale by timestamp; ignore
           }

app/data/subscription-issue-store.test.js

@@ -66,6 +66,82 @@ describe('subscription issue store', () => {
     expect(after).toBe(before); // identity preserved
   });
 
+  test('preserves comments when upsert omits comments', () => {
+    const store = createSubscriptionIssueStore('s1');
+    const comments = [{ id: 1, text: 'Existing comment' }];
+    store.applyPush({
+      type: 'snapshot',
+      id: 's1',
+      revision: 1,
+      issues: [
+        {
+          id: 'X',
+          title: 'x',
+          comments,
+          comment_count: 1,
+          created_at: 10_000,
+          updated_at: 10_000,
+          closed_at: null
+        }
+      ]
+    });
+
+    store.applyPush({
+      type: 'upsert',
+      id: 's1',
+      revision: 2,
+      issue: {
+        id: 'X',
+        title: 'X!',
+        comment_count: 1,
+        created_at: 10_000,
+        updated_at: 10_060,
+        closed_at: null
+      }
+    });
+
+    expect(store.getById('X')?.comments).toBe(comments);
+    expect(store.getById('X')?.title).toBe('X!');
+  });
+
+  test('accepts explicit incoming comments on upsert', () => {
+    const store = createSubscriptionIssueStore('s1');
+    store.applyPush({
+      type: 'snapshot',
+      id: 's1',
+      revision: 1,
+      issues: [
+        {
+          id: 'X',
+          title: 'x',
+          comments: [{ id: 1, text: 'Existing comment' }],
+          comment_count: 1,
+          created_at: 10_000,
+          updated_at: 10_000,
+          closed_at: null
+        }
+      ]
+    });
+
+    store.applyPush({
+      type: 'upsert',
+      id: 's1',
+      revision: 2,
+      issue: {
+        id: 'X',
+        title: 'X!',
+        comments: [],
+        comment_count: 0,
+        created_at: 10_000,
+        updated_at: 10_060,
+        closed_at: null
+      }
+    });
+
+    expect(store.getById('X')?.comments).toEqual([]);
+    expect(store.getById('X')?.comment_count).toBe(0);
+  });
+
   test('ignores stale upsert by revision and timestamp', () => {
     const store = createSubscriptionIssueStore('s1');
     store.applyPush({