Added check for duplicate email and username

common/djangoapps/user_api/api/account.py

@@ -1,11 +1,13 @@
 """Python API for user accounts.
 
+
 Account information includes a student's username, password, and email
 address, but does NOT include user profile information (i.e., demographic
 information and preferences).
 
 """
 from django.db import transaction, IntegrityError
+from django.db.models import Q
 from django.core.validators import validate_email, validate_slug, ValidationError
 from user_api.models import User, UserProfile, Registration, PendingEmailChange
 from user_api.helpers import intercept_errors
@@ -138,6 +140,34 @@ def create_account(username, password, email):
     return registration.activation_key
 
 
+def check_account_exists(username=None, email=None):
+    """Check whether an account with a particular username or email already exists.
+
+    Keyword Arguments:
+        username (unicode)
+        email (unicode)
+
+    Returns:
+        list of conflicting fields
+
+    Example Usage:
+        >>> account_api.check_account_exists(username="bob")
+        []
+        >>> account_api.check_account_exists(username="ted", email="ted@example.com")
+        ["email", "username"]
+
+    """
+    conflicts = []
+
+    if email is not None and User.objects.filter(email=email).exists():
+        conflicts.append("email")
+
+    if username is not None and User.objects.filter(username=username).exists():
+        conflicts.append("username")
+
+    return conflicts
+
+
 @intercept_errors(AccountInternalError, ignore_errors=[AccountRequestError])
 def account_info(username):
     """Retrieve information about a user's account.