Fix fetching of community posts (fixes #4283)

Also use spawn_try_task to fetch community outbox, mods etc to avoid
delay/timeout when fetching new community.

api_tests/src/community.spec.ts

@@ -480,3 +480,25 @@ test("Dont receive community activities after unsubscribe", async () => {
   let postResBeta = searchPostLocal(beta, postRes.post_view.post);
   expect((await postResBeta).posts.length).toBe(0);
 });
+
+test("Fetch community, includes posts", async () => {
+  let communityRes = await createCommunity(alpha);
+  expect(communityRes.community_view.community.name).toBeDefined();
+  expect(communityRes.community_view.counts.subscribers).toBe(1);
+
+  let postRes = await createPost(alpha, communityRes.community_view.community.id);
+  expect(postRes.post_view.post).toBeDefined();
+
+  let resolvedCommunity = await waitUntil(
+    () => resolveCommunity(beta, communityRes.community_view.community.actor_id),
+    c => c.community?.community.id != undefined,
+  );
+  let betaCommunity = resolvedCommunity.community;
+  expect(betaCommunity?.community.actor_id).toBe(communityRes.community_view.community.actor_id);
+
+  await longDelay();
+
+  let post_listing = await getPosts(beta, 'All');
+  expect(post_listing.posts.length).toBe(1);
+  expect(post_listing.posts[0].post.ap_id).toBe(postRes.post_view.post.ap_id);
+});

crates/apub/src/collections/community_outbox.rs

@@ -96,11 +96,21 @@ impl Collection for ApubCommunityOutbox {
     // process items in parallel, to avoid long delay from fetch_site_metadata() and other processing
     join_all(outbox_activities.into_iter().map(|activity| {
       async {
-        // use separate request counter for each item, otherwise there will be problems with
-        // parallel processing
-        let verify = activity.verify(data).await;
-        if verify.is_ok() {
-          activity.receive(data).await.ok();
+        // Receiving announce requires at least one local community follower for anti spam purposes.
+        // This won't be the case for newly fetched communities, so we extract the inner activity
+        // and handle it directly to bypass this check.
+        let inner: Option<AnnouncableActivities> = activity
+          .object
+          .object(data)
+          .await
+          .ok()
+          .map(|o| o.try_into().ok())
+          .flatten();
+        if let Some(AnnouncableActivities::CreateOrUpdatePost(inner)) = inner {
+          let verify = inner.verify(data).await;
+          if verify.is_ok() {
+            inner.receive(data).await.ok();
+          }
         }
       }
     }))

crates/apub/src/objects/community.rs

@@ -28,9 +28,8 @@ use lemmy_db_schema::{
   traits::{ApubActor, Crud},
 };
 use lemmy_db_views_actor::structs::CommunityFollowerView;
-use lemmy_utils::{error::LemmyError, utils::markdown::markdown_to_html};
+use lemmy_utils::{error::LemmyError, spawn_try_task, utils::markdown::markdown_to_html};
 use std::ops::Deref;
-use tracing::debug;
 use url::Url;
 
 #[derive(Clone, Debug)]
@@ -142,21 +141,16 @@ impl Object for ApubCommunity {
 
     // Fetching mods and outbox is not necessary for Lemmy to work, so ignore errors. Besides,
     // we need to ignore these errors so that tests can work entirely offline.
-    let fetch_outbox = group.outbox.dereference(&community, context);
-    let fetch_followers = group.followers.dereference(&community, context);
-
-    if let Some(moderators) = group.attributed_to {
-      let fetch_moderators = moderators.dereference(&community, context);
-      // Fetch mods, outbox and followers in parallel
-      let res = tokio::join!(fetch_outbox, fetch_moderators, fetch_followers);
-      res.0.map_err(|e| debug!("{}", e)).ok();
-      res.1.map_err(|e| debug!("{}", e)).ok();
-      res.2.map_err(|e| debug!("{}", e)).ok();
-    } else {
-      let res = tokio::join!(fetch_outbox, fetch_followers);
-      res.0.map_err(|e| debug!("{}", e)).ok();
-      res.1.map_err(|e| debug!("{}", e)).ok();
-    }
+    let community_ = community.clone();
+    let context_ = context.reset_request_count();
+    spawn_try_task(async move {
+      group.outbox.dereference(&community_, &context_).await?;
+      group.followers.dereference(&community_, &context_).await?;
+      if let Some(moderators) = group.attributed_to {
+        moderators.dereference(&community_, &context_).await?;
+      }
+      Ok(())
+    });
 
     Ok(community)
   }