Move 'ns not found' into mongo adapter.

src/Adapters/Storage/Mongo/MongoStorageAdapter.js

@@ -70,8 +70,15 @@ export class MongoStorageAdapter {
     });
   }
 
-  dropCollection(name: string) {
-    return this.collection(this._collectionPrefix + name).then(collection => collection.drop());
+  dropCollection(className: string) {
+    return this.collection(this._collectionPrefix + className).then(collection => collection.drop())
+    .catch(error => {
+      // 'ns not found' means collection was already gone. Ignore deletion attempt.
+      if (error.message == 'ns not found') {
+        return Promise.resolve();
+      }
+      return Promise.reject(error);
+    });
   }
 
   // Used for testing only right now.

src/Controllers/DatabaseController.js

@@ -44,10 +44,6 @@ DatabaseController.prototype.collectionExists = function(className) {
   return this.adapter.collectionExists(className);
 };
 
-DatabaseController.prototype.dropCollection = function(className) {
-  return this.adapter.dropCollection(className);
-};
-
 DatabaseController.prototype.validateClassName = function(className) {
   if (this.skipValidation) {
     return Promise.resolve();

src/Routers/SchemasRouter.js

@@ -93,7 +93,7 @@ var removeJoinTables = (database, mongoSchema) => {
     .filter(field => mongoSchema[field].startsWith('relation<'))
     .map(field => {
       let collectionName = `_Join:${field}:${mongoSchema._id}`;
-      return database.dropCollection(collectionName);
+      return database.adapter.dropCollection(collectionName);
     })
   );
 };
@@ -117,17 +117,7 @@ function deleteSchema(req) {
           return removeJoinTables(req.config.database, document);
         });
     })
-    .then(() => {
-      // Success
-      return { response: {} };
-    }, error => {
-      if (error.message == 'ns not found') {
-        // If they try to delete a non-existent class, that's fine, just let them.
-        return { response: {} };
-      }
-
-      return Promise.reject(error);
-    });
+    .then(() => ({ response: {} }));
 }
 
 export class SchemasRouter extends PromiseRouter {

src/Schema.js

@@ -525,15 +525,7 @@ class Schema {
       if (this.data[className][fieldName].type == 'Relation') {
         //For relations, drop the _Join table
         return database.adapter.deleteFields(className, [fieldName], [])
-        .then(() => database.dropCollection(`_Join:${fieldName}:${className}`))
-        .catch(error => {
-          // 'ns not found' means collection was already gone. Ignore deletion attempt.
-          // TODO: 'ns not found' is a mongo implementation detail. Move it into mongo adapter.
-          if (error.message == 'ns not found') {
-            return Promise.resolve();
-          }
-          return Promise.reject(error);
-        });
+        .then(() => database.adapter.dropCollection(`_Join:${fieldName}:${className}`));
       }
 
       const fieldNames = [fieldName];