Fix get_subreddit_info crash when redditwarp raises KeyError

When Reddit removes fields from their API response (e.g.
active_user_count), redditwarp's Subreddit model construction
raises KeyError. This adds a fallback that catches KeyError
and uses a raw API call to return basic subreddit info.

Fixes #6

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: johntrandall

src/mcp_server_reddit/server.py

@@ -115,7 +115,25 @@ def get_frontpage_posts(self, limit: int = 10) -> list[Post]:
 
     def get_subreddit_info(self, subreddit_name: str) -> SubredditInfo:
         """Get information about a subreddit"""
-        subr = self.client.p.subreddit.fetch_by_name(subreddit_name)
+        try:
+            subr = self.client.p.subreddit.fetch_by_name(subreddit_name)
+        except KeyError as exc:
+            # redditwarp's Subreddit model uses bracket access on fields that
+            # Reddit may have removed from the API (e.g. active_user_count).
+            # Fall back to a raw API call to get basic subreddit info.
+            import logging
+            logging.getLogger(__name__).warning(
+                "redditwarp model construction failed for r/%s: %s. "
+                "Using fallback.",
+                subreddit_name, exc,
+            )
+            root = self.client.request('GET', f'/r/{subreddit_name}/about')
+            data = root['data']
+            return SubredditInfo(
+                name=data.get('display_name', subreddit_name),
+                subscriber_count=data.get('subscribers', -1),
+                description=data.get('public_description'),
+            )
         return SubredditInfo(
             name=subr.name,
             subscriber_count=subr.subscriber_count,

tests/__init__.py

@@ -0,0 +1,87 @@
+"""Tests for mcp-server-reddit server logic."""
+
+from unittest.mock import MagicMock, patch, PropertyMock
+
+import pytest
+
+from mcp_server_reddit.server import RedditServer, SubredditInfo
+
+
+class TestGetSubredditInfo:
+    """Test get_subreddit_info with normal and fallback paths."""
+
+    def _make_server_with_mock_client(self):
+        """Create a RedditServer with a mocked redditwarp client."""
+        with patch.object(RedditServer, '__init__', lambda self: None):
+            server = RedditServer()
+            server.client = MagicMock()
+            return server
+
+    def test_normal_path(self):
+        """Returns SubredditInfo when redditwarp model construction succeeds."""
+        server = self._make_server_with_mock_client()
+
+        mock_subr = MagicMock()
+        mock_subr.name = 'python'
+        mock_subr.subscriber_count = 1200000
+        mock_subr.public_description = 'News about Python'
+        server.client.p.subreddit.fetch_by_name.return_value = mock_subr
+
+        result = server.get_subreddit_info('python')
+
+        assert isinstance(result, SubredditInfo)
+        assert result.name == 'python'
+        assert result.subscriber_count == 1200000
+        assert result.description == 'News about Python'
+
+    def test_fallback_on_keyerror(self):
+        """Falls back to raw API when redditwarp raises KeyError.
+
+        This happens when Reddit removes fields from the API response
+        that redditwarp expects (e.g. active_user_count).
+        """
+        server = self._make_server_with_mock_client()
+
+        # Simulate redditwarp KeyError during model construction
+        server.client.p.subreddit.fetch_by_name.side_effect = KeyError('active_user_count')
+
+        # Mock the raw API fallback
+        server.client.request.return_value = {
+            'data': {
+                'display_name': 'python',
+                'subscribers': 1200000,
+                'public_description': 'News about Python',
+            }
+        }
+
+        result = server.get_subreddit_info('python')
+
+        assert isinstance(result, SubredditInfo)
+        assert result.name == 'python'
+        assert result.subscriber_count == 1200000
+        assert result.description == 'News about Python'
+        server.client.request.assert_called_once_with('GET', '/r/python/about')
+
+    def test_fallback_with_missing_fields(self):
+        """Fallback handles missing fields gracefully with defaults."""
+        server = self._make_server_with_mock_client()
+        server.client.p.subreddit.fetch_by_name.side_effect = KeyError('active_user_count')
+
+        # Minimal API response — missing optional fields
+        server.client.request.return_value = {
+            'data': {}
+        }
+
+        result = server.get_subreddit_info('test_sub')
+
+        assert result.name == 'test_sub'  # falls back to argument
+        assert result.subscriber_count == -1  # default
+        assert result.description is None
+
+    def test_non_keyerror_exceptions_propagate(self):
+        """Non-KeyError exceptions are not caught by the fallback."""
+        server = self._make_server_with_mock_client()
+        server.client.p.subreddit.fetch_by_name.side_effect = ConnectionError('network down')
+
+        with pytest.raises(ConnectionError):
+            server.get_subreddit_info('python')