AttachmentDownloads: Wait for job completion, validate active job list

ts/messageModifiers/AttachmentDownloads.ts

@@ -195,9 +195,47 @@ async function _maybeStartJob(): Promise<void> {
     const job = jobs[i];
     const existing = _activeAttachmentDownloadJobs[job.id];
     if (existing) {
-      logger.warn(`_maybeStartJob: Job ${job.id} is already running`);
+      logger.warn(
+        `attachment_downloads/_maybeStartJob: Job ${job.id} is already running`
+      );
     } else {
-      _activeAttachmentDownloadJobs[job.id] = _runJob(job);
+      logger.info(
+        `attachment_downloads/_maybeStartJob: Starting job ${job.id}`
+      );
+      const promise = _runJob(job);
+      _activeAttachmentDownloadJobs[job.id] = promise;
+
+      const postProcess = async () => {
+        const logId = `attachment_downloads/_maybeStartJob/postProcess/${job.id}`;
+        try {
+          await promise;
+          if (_activeAttachmentDownloadJobs[job.id]) {
+            throw new Error(
+              `${logId}: Active attachments jobs list still has this job!`
+            );
+          }
+        } catch (error: unknown) {
+          log.error(
+            `${logId}: Download job threw an error, deleting.`,
+            Errors.toLogFormat(error)
+          );
+
+          delete _activeAttachmentDownloadJobs[job.id];
+          try {
+            await removeAttachmentDownloadJob(job.id);
+          } catch (deleteError) {
+            log.error(
+              `${logId}: Failed to delete attachment job`,
+              Errors.toLogFormat(error)
+            );
+          } finally {
+            _maybeStartJob();
+          }
+        }
+      };
+
+      // Note: intentionally not awaiting
+      postProcess();
     }
   }
 }
@@ -305,7 +343,6 @@ async function _runJob(job?: AttachmentDownloadJobType): Promise<void> {
       Errors.toLogFormat(error)
     );
 
-    try {
     // Remove `pending` flag from the attachment.
     await _addAttachmentToMessage(
       message,
@@ -330,10 +367,6 @@ async function _runJob(job?: AttachmentDownloadJobType): Promise<void> {
     };
 
     await saveAttachmentDownloadJob(failedJob);
-    } finally {
-      delete _activeAttachmentDownloadJobs[id];
-      _maybeStartJob();
-    }
   }
 }