storage: make pymongo and redis dependency optional

Fail only if the module required by the storage wrapper is not
available. Since the library is usable without any persistent storage
driver at all, the database-specific module requirements have been
moved to extras_require.

Author: bajnokk

setup.py

@@ -12,7 +12,9 @@
     description='OpenID Connect Provider (OP) library in Python.',
     install_requires=[
         'oic >= 1.2.1',
+    ],
+    extras_require=[
         'pymongo',
-        'redis'
+        'redis',
     ]
 )

src/pyop/storage.py

@@ -3,10 +3,22 @@
 from abc import ABC, abstractmethod
 import copy
 import json
-import pymongo
-from redis.client import Redis
 from datetime import datetime
 
+try:
+    import pymongo
+except ImportError:
+    _has_pymongo = False
+else:
+    _has_pymongo = True
+
+try:
+    from redis.client import Redis
+except ImportError:
+    _has_redis = False
+else:
+    _has_redis = True
+
 
 class StorageBase(ABC):
     _ttl = None
@@ -55,6 +67,8 @@ def ttl(self):
 
 class MongoWrapper(StorageBase):
     def __init__(self, db_uri, db_name, collection, ttl=None):
+        if not _has_pymongo:
+            raise ImportError("pymongo module is required but it is not available")
         self._db_uri = db_uri
         self._coll_name = collection
         self._db = MongoDB(db_uri, db_name=db_name)
@@ -105,6 +119,8 @@ class RedisWrapper(StorageBase):
     """
 
     def __init__(self, db_uri, collection, ttl=None):
+        if not _has_redis:
+            raise ImportError("redis module is required but it is not available")
         self._db = Redis.from_url(db_uri, decode_responses=True)
         self._collection = collection
         if ttl is None or (isinstance(ttl, int) and ttl >= 0):

tests/pyop/test_storage.py

@@ -11,7 +11,7 @@
 import pymongo
 import time
 
-from pyop.storage import StorageBase
+import pyop.storage
 
 __author__ = 'lundberg'
 
@@ -32,7 +32,9 @@ def mock_mongo():
 class TestStorage(object):
     @pytest.fixture(params=uri_list)
     def db(self, request):
-        return StorageBase.from_uri(request.param, db_name="pyop", collection='test')
+        return pyop.storage.StorageBase.from_uri(
+            request.param, db_name="pyop", collection="test"
+        )
 
     def test_write(self, db):
         db['foo'] = 'bar'
@@ -79,7 +81,7 @@ def test_items(self, db):
         ],
     )
     def test_from_uri(self, args, kwargs):
-        store = StorageBase.from_uri(*args, **kwargs)
+        store = pyop.storage.StorageBase.from_uri(*args, **kwargs)
         store["test"] = "value"
         assert store["test"] == "value"
 
@@ -118,12 +120,12 @@ def test_from_uri(self, args, kwargs):
     )
     def test_from_uri_invalid_parameters(self, error, args, kwargs):
         with pytest.raises(error):
-            StorageBase.from_uri(*args, **kwargs)
+            pyop.storage.StorageBase.from_uri(*args, **kwargs)
 
 
 class StorageTTLTest(ABC):
     def prepare_db(self, uri, ttl):
-        self.db = StorageBase.from_uri(
+        self.db = pyop.storage.StorageBase.from_uri(
             uri,
             collection="test",
             ttl=ttl,
@@ -169,6 +171,13 @@ def new_time():
     def test_ttl(self):
         self.execute_ttl_test("redis://localhost/0", 3600)
 
+    def test_missing_module(self):
+        pyop.storage._has_redis = False
+        self.prepare_db("mongodb://localhost/0", None)
+        with pytest.raises(ImportError):
+            self.prepare_db("redis://localhost/0", None)
+        pyop.storage._has_redis = True
+
 
 class TestMongoTTL(StorageTTLTest):
     def set_time(self, offset, monkeypatch):
@@ -180,3 +189,10 @@ def new_time():
 
     def test_ttl(self):
         self.execute_ttl_test("mongodb://localhost/pyop", 3600)
+
+    def test_missing_module(self):
+        pyop.storage._has_pymongo = False
+        self.prepare_db("redis://localhost/0", None)
+        with pytest.raises(ImportError):
+            self.prepare_db("mongodb://localhost/0", None)
+        pyop.storage._has_pymongo = True