Refactor hot reload logic into separate module#1365
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Extract file-watcher logic from bin.py into a new mesop/server/hot_reload.py
module so it can be shared by both the mesop CLI and the WSGI integration.
Add a `watch_path` parameter to `create_wsgi_app()`: when provided alongside
`debug_mode=True`, a background watchdog thread is started immediately so that
hot reloading works when Mesop is mounted inside FastAPI, Starlette, Gunicorn,
or any other WSGI-compatible server.
Usage:
mesop_app = create_wsgi_app(debug_mode=True, watch_path=__file__)
Also add THIRD_PARTY_PY_WATCHDOG to build_defs/defaults.bzl and update the
server/BUILD and bin/BUILD targets accordingly.
https://claude.ai/code/session_01U3KhAZacaA9FpVT1jzGeYn
Dict keys that are Python tuples (e.g. (1, 2)) were not handled correctly in two places: 1. diff_state: DeepDiff incorrectly expanded the tuple into multiple path segments, producing ["val1", 1, 2] instead of the correct single element ["val1", "(1, 2)"]. The fix normalises both state objects with a new _normalize_state_for_diff helper before passing them to DeepDiff. The helper converts any non-JSON-scalar dict key (tuple, frozenset, etc.) to its str() representation so DeepDiff emits an unambiguous, single path element like "(1, 2)". 2. serialize_dataclass: json.dumps raised TypeError for dicts with tuple keys because JSON only supports string keys. The same normalisation is now applied to the asdict() output before encoding. The TypeScript applyStateDiff already handles arbitrary string path elements correctly, so no frontend changes are required beyond a new test that exercises the "(1, 2)" string-key path. https://claude.ai/code/session_01U3KhAZacaA9FpVT1jzGeYn
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Summary
Extracted hot reload functionality from
mesop/bin/bin.pyinto a new dedicated modulemesop/server/hot_reload.pyto improve code organization and enable hot reload support in WSGI server environments.Key Changes
New module: Created
mesop/server/hot_reload.pycontaining:execute_main_module()- executes the main app module with error handlingstart_file_watcher()- starts a background daemon thread for file watchingfs_watcher()- filesystem watcher implementation using watchdogReloadEventHandler- handles file system events (modified, created, deleted)clear_app_modules,add_app_module,remove_app_module)Updated
mesop/bin/bin.py:mesop.server.hot_reload)start_file_watcher()instead of managing threads directlythreading,time,watchdog, etc.)execute_main_module()call to passprod_modeparameterEnhanced
mesop/server/wsgi_app.py:watch_pathparameter tocreate_wsgi_app()functiondebug_mode=Trueandwatch_pathis providedBuild configuration updates:
THIRD_PARTY_PY_WATCHDOGdependency definition inbuild_defs/defaults.bzlmesop/server/BUILDto include watchdog dependency and necessary importsmesop/bin/BUILDto depend on//mesop/serverinstead of individual modulesImplementation Details
prod_modeparameter is now threaded through the hot reload pipeline to control error reporting behaviorapp_modules.remove()toapp_modules.discard()for safer module removalhttps://claude.ai/code/session_01U3KhAZacaA9FpVT1jzGeYn