Finding areas that are untested and need love (#4131)

* Makes InstallationRouter like others

* Adds testing for Range file requests

- Fixes issue with small requests (0-2)

* Revert "Makes InstallationRouter like others"

This reverts commit e2d2a16ebf2757db6138c7b5b33c97c56c69ead6.

* Better handling of errors in FilesRouter

* Fix incorrectness in range requests

* Better/simpler logic

* Only on mongo at it requires Gridstore

* Open file streaming to all adapters supporting it

* Improves coverage of parsers

* Ensures depreciation warning is effective

* Removes unused function

* de-duplicate logic

* Removes necessity of overriding req.params.className on subclasses routers

* Use babel-preset-env to ensure min-version compatible code

* removes dead code

* Leverage indexes in order to infer which field is duplicated upon signup

- A note mentioned that it would be possible to leverage using the indexes on username/email to infer which is duplicated

* Small nit

* Better template to match column name

* Restores original implementation for safety

* nits

src/RestWrite.js

@@ -1011,9 +1011,19 @@ RestWrite.prototype.runDatabaseOperation = function() {
         if (this.className !== '_User' || error.code !== Parse.Error.DUPLICATE_VALUE) {
           throw error;
         }
+
+        // Quick check, if we were able to infer the duplicated field name
+        if (error && error.userInfo && error.userInfo.duplicated_field === 'username') {
+          throw new Parse.Error(Parse.Error.USERNAME_TAKEN, 'Account already exists for this username.');
+        }
+
+        if (error && error.userInfo && error.userInfo.duplicated_field === 'email') {
+          throw new Parse.Error(Parse.Error.EMAIL_TAKEN, 'Account already exists for this email address.');
+        }
+
         // If this was a failed user creation due to username or email already taken, we need to
         // check whether it was username or email and return the appropriate error.
-
+        // Fallback to the original method
         // TODO: See if we can later do this without additional queries by using named indexes.
         return this.config.database.find(
           this.className,