142 Fixing database existance double check (#286)

* Fix exists() double call in client create_database method
* Add throw_on_exists functionality to database create method
* Add logic to database test validating new create functionality

Author: porthunt

CHANGES.rst

@@ -1,6 +1,7 @@
 2.5.0 (Unreleased)
 ==================
 - [FIXED] Fixed ``TypeError`` when setting revision limits on Python>=3.6.
+- [FIXED] Fixed the ``exists()`` double check on ``client.py`` and ``database.py``.
 - [FIXED] Fixed Cloudant exception code 409 with 412 when creating a database that already exists.
 
 2.4.0 (2017-02-14)

src/cloudant/client.py

@@ -23,7 +23,10 @@
 from ._2to3 import bytes_, unicode_
 from .database import CloudantDatabase, CouchDatabase
 from .feed import Feed, InfiniteFeed
-from .error import CloudantArgumentError, CloudantClientException
+from .error import (
+    CloudantArgumentError,
+    CloudantClientException,
+    CloudantDatabaseException)
 from ._common_util import (
     USER_AGENT,
     append_response_error_content,
@@ -224,10 +227,11 @@ def create_database(self, dbname, **kwargs):
         :returns: The newly created database object
         """
         new_db = self._DATABASE_CLASS(self, dbname)
-        if new_db.exists():
-            if kwargs.get('throw_on_exists', True):
+        try:
+            new_db.create(kwargs.get('throw_on_exists', False))
+        except CloudantDatabaseException as ex:
+            if ex.status_code == 412:
                 raise CloudantClientException(412, dbname)
-        new_db.create()
         super(CouchDB, self).__setitem__(dbname, new_db)
         return new_db
 

src/cloudant/database.py

@@ -329,15 +329,19 @@ def get_view_result(self, ddoc_id, view_name, raw_result=False, **kwargs):
         else:
             return view.result
 
-    def create(self):
+    def create(self, throw_on_exists=False):
         """
         Creates a database defined by the current database object, if it
         does not already exist and raises a CloudantException if the operation
         fails.  If the database already exists then this method call is a no-op.
 
+        :param bool throw_on_exists: Boolean flag dictating whether or
+            not to throw a CloudantDatabaseException when attempting to
+            create a database that already exists.
+
         :returns: The database object
         """
-        if self.exists():
+        if not throw_on_exists and self.exists():
             return self
 
         resp = self.r_session.put(self.database_url)

tests/unit/database_tests.py

@@ -202,6 +202,11 @@ def test_create_db_delete_db(self):
             # No issue should arise if attempting to create existing database
             db_2 = db.create()
             self.assertEqual(db, db_2)
+            # If we use throw_on_exists=True, it will raise a
+            # CloudantDatabaseException if the database already exists.
+            with self.assertRaises(CloudantDatabaseException) as cm:
+                db.create(throw_on_exists=True)
+            self.assertEqual(cm.exception.status_code, 412)
         except Exception as err:
             self.fail('Exception {0} was raised.'.format(str(err)))
         finally:
@@ -690,7 +695,7 @@ def test_revisions_diff(self):
         )
         # Test differences
         self.assertEqual(
-            self.db.revisions_diff('julia006', *revs), 
+            self.db.revisions_diff('julia006', *revs),
             {'julia006': {'missing': revs, 'possible_ancestors': [doc['_rev']]}}
         )
         # Test no differences
@@ -1150,7 +1155,7 @@ def test_create_json_index(self):
                  'lists': {},
                  'shows': {},
                  'language': 'query',
-                 'views': {index.name: {'map': {'fields': {'name': 'asc', 
+                 'views': {index.name: {'map': {'fields': {'name': 'asc',
                                                            'age': 'asc'}},
                                         'reduce': '_count',
                                         'options': {'def': {'fields': ['name',
@@ -1241,7 +1246,7 @@ def test_create_multiple_indexes_one_ddoc(self):
                  'lists': {},
                  'shows': {},
                  'views': {'json-index-001': {
-                                'map': {'fields': {'name': 'asc', 
+                                'map': {'fields': {'name': 'asc',
                                                    'age': 'asc'}},
                                         'reduce': '_count',
                                         'options': {'def': {'fields': ['name',
@@ -1258,7 +1263,7 @@ def test_create_multiple_indexes_one_ddoc(self):
                                    'default': 'keyword',
                                    'fields': {'$default': 'standard'}}}}}
             )
-    
+
     def test_create_query_index_failure(self):
         """
         Tests that a type of something other than 'json' or 'text' will cause