Made sure that cache did not over write itself.

src/morethantext/cache.rs

@@ -99,6 +99,18 @@ impl Cache {
         output
     }
 
+    fn next_id(&mut self) -> String {
+        let mut id: String;
+        loop {
+            id = self.ids.next().unwrap();
+            match self.get(&id) {
+                FromCache::Error(_) => break,
+                _ => (),
+            }
+        }
+        id
+    }
+
     pub async fn listen(&mut self, listener: Receiver<ToCache>) {
         loop {
             match listener.recv().await.unwrap() {
@@ -132,7 +144,7 @@ impl Cache {
             }
         };
         for name in data.list() {
-            let id = self.ids.next().unwrap();
+            let id = self.next_id();
             match store.add_by_id(name, &id) {
                 Ok(_) => {
                     self.data.insert(id, FromCache::DB(Database::new()));
@@ -244,6 +256,37 @@ mod engine {
             ),
         }
     }
+
+    #[async_std::test]
+    async fn ids_are_not_overwritten() {
+        let ids = ["first", "first", "second"];
+        let names = ["barney", "fred"];
+        let dir = tempdir().unwrap();
+        let mut cache = Cache::with_ids(dir.path(), ids).await;
+        let mut store1 = Store::new();
+        store1.add(names[0]).unwrap();
+        let mut store2 = Store::new();
+        store2.add(names[1]).unwrap();
+        cache.commit(store1);
+        cache.commit(store2);
+        assert_eq!(
+            cache.data.len(),
+            3,
+            "cache.data had the following entries {:?}",
+            cache.data.keys()
+        );
+    }
+
+    #[async_std::test]
+    async fn no_duplicate_ids() {
+        let ids = ["one", "two"];
+        let dir = tempdir().unwrap();
+        let mut cache = Cache::with_ids(dir.path(), ids).await;
+        cache
+            .data
+            .insert(ids[0].to_string(), FromCache::DB(Database::new()));
+        assert_eq!(cache.next_id(), ids[1]);
+    }
 }
 
 #[cfg(test)]