4 files changed, 88 insertions, 6 deletions

diff --git a/src/mailman/docs/NEWS.rst b/src/mailman/docs/NEWS.rst
index 95663d5ee..0000afb73 100644
--- a/src/mailman/docs/NEWS.rst
+++ b/src/mailman/docs/NEWS.rst
@@ -22,6 +22,12 @@ Configuration
  * The default languages from Mailman 2.1 have been ported over.  Given by
    Aurélien Bompard.
 
+REST
+----
+ * When creating a user via REST using an address that already exists, but
+   isn't linked, the address is linked to the new user.  Given by Aurélien
+   Bompard.
+
 
 3.0.0 -- "Show Don't Tell"
 ==========================
diff --git a/src/mailman/rest/docs/users.rst b/src/mailman/rest/docs/users.rst
index 13390a00f..493cf65e2 100644
--- a/src/mailman/rest/docs/users.rst
+++ b/src/mailman/rest/docs/users.rst
@@ -496,3 +496,35 @@ Gwen, a new users, takes over as a server owner.
     password: {plaintext}...
     self_link: http://localhost:9001/3.0/users/7
     user_id: 7
+
+
+Linking users
+=============
+
+If an address already exists, but is not yet linked to a user, and a new user
+is requested for that address, the user will be linked to the existing
+address.
+
+Herb's address already exists, but no user is linked to it.
+
+    >>> herb = user_manager.create_address('herb@example.com')
+    >>> print(herb.user)
+    None
+    >>> transaction.commit()
+
+Now, a user creation request is received, using Herb's email address.
+
+    >>> dump_json('http://localhost:9001/3.0/users', {
+    ...           'email': 'herb@example.com',
+    ...           'display_name': 'Herb Person',
+    ...           })
+    content-length: 0
+    date: ...
+    location: http://localhost:9001/3.0/users/8
+    server: ...
+    status: 201
+
+Herb's email address is now linked to the new user.
+
+    >>> herb.user
+    <User "Herb Person" (8) at ...
diff --git a/src/mailman/rest/tests/test_users.py b/src/mailman/rest/tests/test_users.py
index ac8d018e8..d58d7f9c3 100644
--- a/src/mailman/rest/tests/test_users.py
+++ b/src/mailman/rest/tests/test_users.py
@@ -160,7 +160,7 @@ class TestUsers(unittest.TestCase):
                      })
         self.assertEqual(cm.exception.code, 400)
         self.assertEqual(cm.exception.reason,
-                         b'Address already exists: anne@example.com')
+                         b'User already exists: anne@example.com')
 
     def test_addresses_of_missing_user_id(self):
         # Trying to get the /addresses of a missing user id results in error.
@@ -190,6 +190,39 @@ class TestUsers(unittest.TestCase):
                      })
         self.assertEqual(cm.exception.code, 404)
 
+    def test_existing_address_link(self):
+        # Creating a user with an existing address links them.
+        user_manager = getUtility(IUserManager)
+        with transaction():
+            user_manager.create_address('anne@example.com')
+        call_api('http://localhost:9001/3.0/users', dict(
+            email='anne@example.com',
+            ))
+        anne = user_manager.get_user('anne@example.com')
+        self.assertEqual(anne.display_name, '')
+        self.assertFalse(anne.is_server_owner)
+        self.assertIn('anne@example.com',
+                      [address.email for address in anne.addresses])
+
+    def test_existing_address_link_with_arguments(self):
+        # Creating a user with an existing address links them, and the
+        # addition arguments get honored.
+        user_manager = getUtility(IUserManager)
+        with transaction():
+            user_manager.create_address('anne@example.com')
+        call_api('http://localhost:9001/3.0/users', dict(
+            email='anne@example.com',
+            display_name='Anne Person',
+            password='123',
+            is_server_owner=True,
+            ))
+        anne = user_manager.get_user('anne@example.com')
+        self.assertEqual(anne.display_name, 'Anne Person')
+        self.assertTrue(anne.is_server_owner)
+        self.assertEqual(anne.password, '{plaintext}123')
+        self.assertIn('anne@example.com',
+                      [address.email for address in anne.addresses])
+
     def test_create_user_twice(self):
         # LP: #1418280.  No additional users should be created when an address
         # that already exists is given.
@@ -207,7 +240,7 @@ class TestUsers(unittest.TestCase):
                 email='anne@example.com'))
         self.assertEqual(cm.exception.code, 400)
         self.assertEqual(cm.exception.reason,
-                         b'Address already exists: anne@example.com')
+                         b'User already exists: anne@example.com')
         # But at least no new users was created.
         content, response = call_api('http://localhost:9001/3.0/users')
         self.assertEqual(content['total_size'], 1)
diff --git a/src/mailman/rest/users.py b/src/mailman/rest/users.py
index 7b1ec8040..4521593d4 100644
--- a/src/mailman/rest/users.py
+++ b/src/mailman/rest/users.py
@@ -96,12 +96,23 @@ def create_user(arguments, response):
     # after the fact if successful.
     password = arguments.pop('password', None)
     is_server_owner = arguments.pop('is_server_owner', False)
+    user_manager = getUtility(IUserManager)
     try:
-        user = getUtility(IUserManager).create_user(**arguments)
+        user = user_manager.create_user(**arguments)
     except ExistingAddressError as error:
-        bad_request(
-            response, 'Address already exists: {}'.format(error.address))
-        return None
+        # The address already exists.  If the address already has a user
+        # linked to it, raise an error, otherwise create a new user and link
+        # it to this address.
+        email = arguments.pop('email')
+        user = user_manager.get_user(email)
+        if user is None:
+            address = user_manager.get_address(email)
+            user = user_manager.create_user(**arguments)
+            user.link(address)
+        else:
+            bad_request(
+                response, 'User already exists: {}'.format(error.address))
+            return None
     if password is None:
         # This will have to be reset since it cannot be retrieved.
         password = generate(int(config.passwords.password_length))