Use the ABC class to declare an abstract class

This allows IDEs and other tools to recognize that the class is abstract and throws the appropriate warnings. It also causes an exception to be thrown before a token is consumed.

(cherry picked from commit 29ea3b0e2617fe88bc4488a900b1f12cc1ca68e5)

asyncpraw/util/token_manager.py

@@ -11,8 +11,10 @@
 """
 import aiofiles
 
+from abc import ABC, abstractmethod
 
-class BaseTokenManager:
+
+class BaseTokenManager(ABC):
     """An abstract class for all token managers."""
 
     def __init__(self):
@@ -32,6 +34,7 @@ def reddit(self, value):
             )
         self._reddit = value
 
+    @abstractmethod
     def post_refresh_callback(self, authorizer):
         """Handle callback that is invoked after a refresh token is used.
 
@@ -43,8 +46,8 @@ def post_refresh_callback(self, authorizer):
         ``refresh_token``.
 
         """
-        raise NotImplementedError("``post_refresh_callback`` must be extended.")
 
+    @abstractmethod
     def pre_refresh_callback(self, authorizer):
         """Handle callback that is invoked before refreshing PRAW's authorization.
 
@@ -56,7 +59,6 @@ def pre_refresh_callback(self, authorizer):
         ``refresh_token``.
 
         """
-        raise NotImplementedError("``pre_refresh_callback`` must be extended.")
 
 
 class FileTokenManager(BaseTokenManager):

tests/unit/test_reddit.py

@@ -16,6 +16,14 @@
 from . import UnitTest
 
 
+class DummyTokenManager(BaseTokenManager):
+    def post_refresh_callback(self, authorizer):
+        pass
+
+    def pre_refresh_callback(self, authorizer):
+        pass
+
+
 class TestReddit(UnitTest):
     REQUIRED_DUMMY_SETTINGS = {
         x: "dummy" for x in ["client_id", "client_secret", "user_agent"]
@@ -182,8 +190,8 @@ async def test_post_ratelimit(self, __, _):
     async def test_read_only__with_authenticated_core(self):
         async with Reddit(
             password=None,
-            token_manager=BaseTokenManager(),
             username=None,
+            token_manager=DummyTokenManager(),
             **self.REQUIRED_DUMMY_SETTINGS,
         ) as reddit:
             assert not reddit.read_only
@@ -210,8 +218,8 @@ async def test_read_only__with_authenticated_core__non_confidential(self):
             client_id="dummy",
             client_secret=None,
             redirect_uri="dummy",
-            token_manager=BaseTokenManager(),
             user_agent="dummy",
+            token_manager=DummyTokenManager(),
         ) as reddit:
             assert not reddit.read_only
             reddit.read_only = True

tests/unit/util/test_token_manager.py

@@ -6,6 +6,7 @@
 from asyncpraw.util.token_manager import BaseTokenManager, FileTokenManager
 
 from .. import UnitTest
+from ..test_reddit import DummyTokenManager
 
 
 class DummyAuthorizer:
@@ -14,25 +15,17 @@ def __init__(self, refresh_token):
 
 
 class TestBaseTokenManager(UnitTest):
-    def test_post_refresh_token_callback__raises_not_implemented(self):
-        manager = BaseTokenManager()
-        with pytest.raises(NotImplementedError) as excinfo:
-            manager.post_refresh_callback(None)
-        assert str(excinfo.value) == "``post_refresh_callback`` must be extended."
-
-    def test_pre_refresh_token_callback__raises_not_implemented(self):
-        manager = BaseTokenManager()
-        with pytest.raises(NotImplementedError) as excinfo:
-            manager.pre_refresh_callback(None)
-        assert str(excinfo.value) == "``pre_refresh_callback`` must be extended."
+    def test_init_base_fail(self):
+        with pytest.raises(TypeError):
+            BaseTokenManager()
 
     def test_reddit(self):
-        manager = BaseTokenManager()
+        manager = DummyTokenManager()
         manager.reddit = "dummy"
         assert manager.reddit == "dummy"
 
     def test_reddit__must_only_be_set_once(self):
-        manager = BaseTokenManager()
+        manager = DummyTokenManager()
         manager.reddit = "dummy"
         with pytest.raises(RuntimeError) as excinfo:
             manager.reddit = None