Fix KeyError when active_user_count is missing from API response

Reddit removed the active_user_count field from some subreddit API
endpoints. The Subreddit model constructor used bracket access
(d['active_user_count']) which raises KeyError when the field is
absent. Changed to d.get('active_user_count') which returns None
for missing keys, falling through to the existing -1 default.

Added tests for Subreddit model construction covering:
- Complete API response (field present with value)
- Field present but None (search results)
- Field absent (new Reddit API behavior)
- Field present with zero value

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

Author: johntrandall

redditwarp/models/subreddit.py

@@ -212,7 +212,7 @@ def __init__(self, d: Mapping[str, Any]) -> None:
 
         self.subscriber_count: int = d['subscribers']
         ("")
-        self.viewing_count: int = -1 if (x := d['active_user_count']) is None else x
+        self.viewing_count: int = -1 if (x := d.get('active_user_count')) is None else x
         ("""
             The number of online users who are subscribed to the subreddit.
 

tests/models/__init__.py

@@ -0,0 +1,89 @@
+
+from __future__ import annotations
+
+import pytest
+
+from redditwarp.models.subreddit import Subreddit
+
+
+def _make_subreddit_data(**overrides) -> dict:
+    """Build a minimal subreddit API response dict.
+
+    All required fields are populated with sensible defaults.
+    Pass keyword arguments to override or remove specific fields.
+    """
+    data = {
+        'id': '2qh1i',
+        'display_name': 'AskReddit',
+        'subreddit_type': 'public',
+        'created_utc': 1201233135.0,
+        'title': 'Ask Reddit...',
+        'public_description': 'A subreddit for asking questions.',
+        'public_description_html': '<p>A subreddit for asking questions.</p>',
+        'description': 'Rules and sidebar text.',
+        'description_html': '<p>Rules and sidebar text.</p>',
+        'submit_text': '',
+        'submit_text_html': None,
+        'submit_text_label': None,
+        'submit_link_label': None,
+        'subscribers': 48000000,
+        'active_user_count': 15000,
+        'submission_type': 'any',
+        'allow_galleries': True,
+        'allow_polls': True,
+        'suggested_comment_sort': None,
+        'over18': False,
+        'quarantine': False,
+        'user_is_moderator': None,
+        'user_is_subscriber': None,
+        'user_flair_enabled_in_sr': None,
+        'user_sr_flair_enabled': None,
+        'user_flair_text': None,
+        'user_flair_css_class': None,
+        'user_flair_background_color': None,
+        'user_flair_text_color': None,
+        'user_flair_template_id': None,
+        'can_assign_user_flair': False,
+        'can_assign_link_flair': False,
+        'user_flair_position': 'right',
+        'link_flair_enabled': True,
+        'link_flair_position': 'left',
+        'has_menu_widget': False,
+    }
+    data.update(overrides)
+    return data
+
+
+class TestSubredditConstruction:
+    """Test Subreddit model construction from API response dicts."""
+
+    def test_basic_construction(self):
+        """Subreddit can be constructed from a complete API response."""
+        data = _make_subreddit_data()
+        subr = Subreddit(data)
+        assert subr.name == 'AskReddit'
+        assert subr.subscriber_count == 48000000
+        assert subr.viewing_count == 15000
+
+    def test_active_user_count_none(self):
+        """viewing_count is -1 when active_user_count is None (e.g., search results)."""
+        data = _make_subreddit_data(active_user_count=None)
+        subr = Subreddit(data)
+        assert subr.viewing_count == -1
+
+    def test_active_user_count_missing(self):
+        """viewing_count is -1 when active_user_count is absent from API response.
+
+        Reddit removed this field from some API endpoints circa 2025.
+        Previously this raised KeyError.
+        """
+        data = _make_subreddit_data()
+        del data['active_user_count']
+        subr = Subreddit(data)
+        assert subr.viewing_count == -1
+
+    def test_active_user_count_zero(self):
+        """viewing_count is 0 when active_user_count is 0."""
+        data = _make_subreddit_data(active_user_count=0)
+        subr = Subreddit(data)
+        assert subr.viewing_count == 0