syncObject: delete 'coms-id' tag on new file if id already in use

app/src/services/sync.js

@@ -177,6 +177,37 @@ const service = {
         else {
           const objId = await service._deriveObjectId(s3Object, path, bucketId);
 
+          // if `coms-id` already in use in COMS, delete the 'coms-id' tag on the new object first,
+          // so that we don't attempt to use a coms-id that's already in use.
+          try {
+            const existingComsId = await objectService.read(objId);
+            if (existingComsId) {
+              const sourceObject = await storageService.getObjectTagging({
+                filePath: path,
+                bucketId: bucketId
+              });
+
+              // Workaround for deleting just the 'coms-id' tag (S3 can only delete ALL tags on an object):
+              //  Retrieve all tags, delete all tags on object, then re-add all keys except 'coms-id'.
+              const objectTags = sourceObject.TagSet.filter(x => !sourceObject.TagSet.includes(x.Key) && x.Key != 'coms-id');
+
+              await storageService.deleteObjectTagging({
+                filePath: path,
+                bucketId: bucketId
+              });
+
+              const data = {
+                bucketId,
+                filePath: path,
+                tags: objectTags
+              };
+
+              await storageService.putObjectTagging(data);
+            }
+          } catch {
+            // no coms-id conflict, proceed as usual
+          }
+
           response = await objectService.create({
             id: objId,
             name: path.match(/(?!.*\/)(.*)$/)[0], // get `name` column