fix: modules losing data after HTTP 304 responses#4180
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When a calendar server responds with 304 (nothing changed since last fetch), the response has no body. CalendarFetcher was parsing it anyway, which produced an empty event list - clearing all previously loaded events and showing nothing on screen. The bug was hidden until MagicMirrorOrg#4120 started forwarding 304 responses through HTTPFetcher instead of silently dropping them. Fix: skip parsing on 304 and re-broadcast the cached events as-is. Also adding unit tests for CalendarFetcher: 304 handling, HTTP error forwarding, parse error resilience, and shouldRefetch boundaries.
KristjanESPERANTO
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khassel
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Jun 6, 2026
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When a server responds with 304 (nothing changed since last fetch), the response has no body. Several modules were trying to parse that empty body anyway - which either cleared their cached data or threw an exception. The result: a blank calendar, empty newsfeed, or missing weather data after the next refresh cycle.
This was reported in the forum: https://forum.magicmirror.builders/topic/20250/calendar-events-broadcasting-nothing-showing
The bug was "introduced" by #4120, which correctly started forwarding 304s to consumers - but not all were ready for it.
Fix
Skip parsing on 304 and keep the existing data as-is:
response.json()