fix(background-sync): properly handle removed repositories

Keep track of accessible repositories during background sync
and remove all issues that do not belong to such repositories
immediately.

This prevents issues hanging on the board that are inaccessible
to the board due to ownership transfer or changed GitHub app
permissions.

Closes #93

packages/app/lib/apps/background-sync/BackgroundSync.js

@@ -1,5 +1,6 @@
 const {
-  filterIssueOrPull
+  filterIssueOrPull,
+  filterRepository
 } = require('../../filters');
 
 const {
@@ -88,10 +89,12 @@ We automatically synchronize all repositories you granted us access to via the G
     return Date.now() - removeClosedLookback;
   }
 
-  async function fetchInstallationIssues(installation, syncClosedSince) {
+  async function fetchInstallationEntities(installation, syncClosedSince) {
 
     const foundIssues = {};
 
+    const foundRepositories = {};
+
     const owner = installation.account.login;
 
     log.debug({ installation: owner }, 'processing');
@@ -109,6 +112,9 @@ We automatically synchronize all repositories you granted us access to via the G
         const owner = repository.owner.login;
         const repo = repository.name;
 
+        // log found repository
+        foundRepositories[repository.id] = filterRepository(repository);
+
         // we ignore archived repositories
         if (repository.archived) {
           log.debug({
@@ -247,32 +253,44 @@ We automatically synchronize all repositories you granted us access to via the G
       log.error({ installation: owner }, 'processing failed', error);
     }
 
-    return foundIssues;
+    return {
+      issues: foundIssues,
+      repositories: foundRepositories
+    };
   }
 
-  async function fetchUpdates(installations, syncClosedSince) {
+  async function fetchEntities(installations, syncClosedSince) {
 
     let foundIssues = {};
+    let foundRepositories = {};
 
     // sync issues
     for (const installation of installations) {
 
-      const installationIssues = await fetchInstallationIssues(installation, syncClosedSince);
+      const installationEntities = await fetchInstallationEntities(installation, syncClosedSince);
 
       foundIssues = {
         ...foundIssues,
-        ...installationIssues
+        ...installationEntities.issues
+      };
+
+      foundRepositories = {
+        ...foundRepositories,
+        ...installationEntities.repositories
       };
     }
 
-    return foundIssues;
+    return {
+      issues: foundIssues,
+      repositories: foundRepositories
+    };
   }
 
-  async function checkExpiration(issues, expiryTime) {
+  async function checkCleanup(issues, repositories, expiryTime) {
 
     let now = Date.now();
 
-    let expired = {};
+    let removedIssues = {};
 
     log.debug('expiration check start');
 
@@ -284,25 +302,40 @@ We automatically synchronize all repositories you granted us access to via the G
         updated_at
       } = issue;
 
+      let expired = false;
+      let removed = false;
+
+      if (!repositories[issue.repository.id]) {
+        log.debug({ issue: key }, 'repository removed');
+
+        removed = true;
+      }
+
       const updatedTime = new Date(updated_at).getTime();
 
       if (updatedTime < expiryTime) {
+        log.debug({ issue: key }, 'issue expired');
 
-        try {
-          log.debug({ issue: key }, 'cleaning up');
+        expired = true;
+      }
 
-          await store.removeIssueById(id);
+      if (!expired && !removed) {
+        continue;
+      }
 
-          expired[id] = issue;
-        } catch (err) {
-          log.error({ issue: key }, 'cleanup failed', err);
-        }
+      try {
+        log.debug({ issue: key }, 'cleaning up');
+        await store.removeIssueById(id);
+
+        removedIssues[id] = issue;
+      } catch (err) {
+        log.error({ issue: key }, 'cleanup failed', err);
       }
     }
 
     log.debug({ t: Date.now() - now }, 'expiration check done');
 
-    return expired;
+    return removedIssues;
   }
 
   async function doSync(installations) {
@@ -311,12 +344,16 @@ We automatically synchronize all repositories you granted us access to via the G
 
     // search existing issues
 
-    const foundIssues = await fetchUpdates(installations, getSyncClosedSince());
+    const {
+      issues: foundIssues,
+      repositories: foundRepositories
+    } = await fetchEntities(installations, getSyncClosedSince());
 
     log.debug(
       { t: Date.now() - t },
-      'found %s issues',
-      Object.keys(foundIssues).length
+      'found %s issues in %s repositories',
+      Object.keys(foundIssues).length,
+      Object.keys(foundRepositories).length
     );
 
     const pendingUpdates = Object.values(foundIssues).filter(update => update);
@@ -357,13 +394,13 @@ We automatically synchronize all repositories you granted us access to via the G
         .filter(k => !(k in foundIssues))
         .map(k => knownIssues[k]);
 
-    const expiredIssues = await checkExpiration(missingIssues, getRemoveClosedBefore());
+    const removedIssues = await checkCleanup(missingIssues, foundRepositories, getRemoveClosedBefore());
 
     log.info(
       { t: Date.now() - t },
-      'updated %s, expired %s issues',
+      'updated %s, removed %s issues',
       pendingUpdates.length,
-      Object.keys(expiredIssues).length
+      Object.keys(removedIssues).length
     );
   }