fix(server): watching a pull request again no longer repeats news the thread already got

apps/server/src/orchestration-v2/Orchestrator.ts

@@ -534,8 +534,10 @@ function withPullRequestWatch(
   link: ThreadPullRequestLink,
   watch: ThreadPullRequestWatch | undefined,
 ): ThreadPullRequestLink {
-  const { watch: _previous, ...rest } = link;
-  return watch === undefined ? rest : { ...rest, watch };
+  const { watch: previous, endedWatch, ...rest } = link;
+  if (watch !== undefined) return { ...rest, watch };
+  const ended = previous ?? endedWatch;
+  return ended === undefined ? rest : { ...rest, endedWatch: ended };
 }
 
 function legacyPullRequestLink(
@@ -544,6 +546,9 @@ function legacyPullRequestLink(
   now: DateTime.Utc,
 ): ThreadPullRequestLink {
   const key = legacyThreadPullRequestKey(linked);
+  const existing = threadPullRequestsOf(thread).find((link) =>
+    threadPullRequestKeysEqual(link, key),
+  );
   return withPullRequestWatch(
     {
       ...key,
@@ -552,8 +557,9 @@ function legacyPullRequestLink(
       linkedAt: DateTime.formatIso(now),
       snapshot: null,
       stack: null,
+      ...(existing?.endedWatch && { endedWatch: existing.endedWatch }),
     },
-    threadPullRequestsOf(thread).find((link) => threadPullRequestKeysEqual(link, key))?.watch,
+    existing?.watch,
   );
 }
 
@@ -3104,6 +3110,7 @@ const makeOrchestrator = Effect.fn("orchestrationV2.Orchestrator.layer")(functio
           const linked = threadPullRequestsOf(thread);
           const visible = (link: ThreadPullRequestLink) =>
             link.source !== "stack-dismissed" && threadPullRequestKeysEqual(link, key);
+          const dismissed = linked.find((link) => threadPullRequestKeysEqual(link, key));
           const links =
             command.type === "thread.pull-request.watch" &&
             command.watching &&
@@ -3118,6 +3125,7 @@ const makeOrchestrator = Effect.fn("orchestrationV2.Orchestrator.layer")(functio
                     linkedAt: startedAt,
                     snapshot: null,
                     stack: null,
+                    ...(dismissed?.endedWatch && { endedWatch: dismissed.endedWatch }),
                   },
                 ]
               : linked;
@@ -3136,16 +3144,30 @@ const makeOrchestrator = Effect.fn("orchestrationV2.Orchestrator.layer")(functio
                     failedChecks: [],
                     passed: false,
                     passedChecks: [],
+                    conflicting: false,
+                    // Watching again must not repeat check or conflict news the last watch told.
+                    ...(existing.endedWatch && {
+                      headSha: existing.endedWatch.headSha,
+                      failedChecks: existing.endedWatch.failedChecks,
+                      passed: existing.endedWatch.passed,
+                      passedChecks: existing.endedWatch.passedChecks,
+                      conflicting: existing.endedWatch.conflicting,
+                    }),
                     remarksThrough: startedAt,
                     remarkIds: [],
-                    conflicting: false,
                     wakes: 0,
                   });
           if (watch === existing.watch && links === linked) return thread;
+          const final =
+            command.type === "thread.pull-request-watch.sync" && watch === undefined
+              ? command.endedWatch
+              : undefined;
           return {
             ...thread,
             pullRequests: links.map((link) =>
-              link === existing ? withPullRequestWatch(link, watch) : link,
+              link === existing
+                ? withPullRequestWatch(final ? { ...link, watch: final } : link, watch)
+                : link,
             ),
             updatedAt: command.type === "thread.pull-request.watch" ? now : thread.updatedAt,
           };

apps/server/src/orchestration-v2/PullRequestWatchReactor.ts

@@ -259,6 +259,7 @@ export const make = Effect.gen(function* () {
     target: WatchTarget,
     next: ThreadPullRequestWatch | null,
     wake?: { readonly text: string; readonly notification: OrchestrationV2Notification },
+    endedWatch?: ThreadPullRequestWatch,
   ) =>
     Effect.gen(function* () {
       const uuid = yield* crypto.randomUUIDv4();
@@ -269,6 +270,7 @@ export const make = Effect.gen(function* () {
         ...identityOf(target.link),
         startedAt: target.watch.startedAt,
         watch: next,
+        ...(endedWatch === undefined ? {} : { endedWatch }),
         ...(wake === undefined
           ? {}
           : { wake: { ...wake, messageId: MessageId.make(`message:pr-watch:${uuid}`) } }),
@@ -477,16 +479,18 @@ export const make = Effect.gen(function* () {
     yield* eachTarget(group, (target) => {
       const report = evaluatePullRequestWatch(target.watch, detail, remarks);
       if (report.changes.length > 0) {
-        return record(
-          target,
-          report.exhausted ? null : report.next,
-          pullRequestWatchMessage({
-            number: target.link.number,
-            url: target.link.url,
-            baseBranch: detail.baseBranch,
-            headSha: report.next.headSha,
-            report,
-          }),
+        const wake = pullRequestWatchMessage({
+          number: target.link.number,
+          url: target.link.url,
+          baseBranch: detail.baseBranch,
+          headSha: report.next.headSha,
+          report,
+        });
+        // An ending watch keeps what this pass saw, so watching again starts from it.
+        return (
+          report.exhausted
+            ? record(target, null, wake, report.next)
+            : record(target, report.next, wake)
         ).pipe(
           Effect.tap(() => woke(target)),
           Effect.tap(() => (report.exhausted ? ended(target, "comment-limit") : Effect.void)),