A better way to ensure that the components cache won't be rewritten unless changed.

- Compare the serialized versions of the cache before and after, minus
  the saved/loaded timestamps, rather than marking the cache as dirty
  after a set.

- `Date` and `DateTime` schema fields should have static default values,
  or those values will change on every run.

- Always sort all the sets before serializing them.

platypush/plugins/inspect/__init__.py

@@ -4,6 +4,7 @@ import json
 import os
 import pathlib
 import pkgutil
+from copy import deepcopy
 from concurrent.futures import Future, ThreadPoolExecutor
 from typing import List, Optional
 
@@ -70,6 +71,9 @@ class InspectPlugin(Plugin):
         """
         cache_version_differs = self._cache.version != Cache.cur_version
         force = force or cache_version_differs
+        old_cache = deepcopy(self._cache.to_dict())
+        old_cache.pop('loaded_at', None)
+        old_cache.pop('saved_at', None)
 
         with self._cache.lock(), auto_mocks(), override_definitions(), ThreadPoolExecutor(
             self._num_workers
@@ -101,7 +105,11 @@ class InspectPlugin(Plugin):
             while futures:
                 futures.pop().result()
 
-        if self._cache.has_changes:
+        new_cache = self._cache.to_dict()
+        new_cache.pop('loaded_at', None)
+        new_cache.pop('saved_at', None)
+
+        if old_cache != new_cache or cache_version_differs:
             self.logger.info('Saving new components cache to %s', self.cache_file)
             self._cache.dump(self.cache_file)
             self._cache.loaded_at = self._cache.saved_at

platypush/schemas/__init__.py

@@ -3,7 +3,6 @@ from enum import Enum
 from typing import Any, Optional, Type, Union
 
 from dateutil.parser import isoparse
-from dateutil.tz import tzutc
 from marshmallow import fields
 
 
@@ -38,7 +37,7 @@ class DateTime(Function):  # lgtm [py/missing-call-to-init]
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.metadata = {
-            'example': datetime.now(tz=tzutc()).isoformat(),
+            'example': '2020-01-01T00:00:00+00:00',
             **(self.metadata or {}),
         }
 
@@ -55,7 +54,7 @@ class Date(Function):  # lgtm [py/missing-call-to-init]
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.metadata = {
-            'example': date.today().isoformat(),
+            'example': '2020-01-01',
             **(self.metadata or {}),
         }
 

platypush/utils/manifest.py

@@ -274,12 +274,15 @@ class Dependencies:
     def to_dict(self):
         return {
             'before': self.before,
-            'packages': list(self.packages),
+            'packages': sorted(self.packages),
-            'pip': self.pip,
+            'pip': sorted(self.pip),
             'after': self.after,
             'by_pkg_manager': {
-                pkg_manager.value.executable: list(pkgs)
+                pkg_manager.value.executable: sorted(pkgs)
-                for pkg_manager, pkgs in self.by_pkg_manager.items()
+                for pkg_manager, pkgs in sorted(
+                    self.by_pkg_manager.items(),
+                    key=lambda item: item[0].value.executable,
+                )
             },
         }
 
@@ -560,7 +563,9 @@ class Manifest(ABC):
     def _init_events(
         events: Union[Iterable[str], Mapping[str, Optional[str]]]
     ) -> Dict[Type, str]:
-        evt_dict = events if isinstance(events, Mapping) else {e: None for e in events}
+        evt_dict = (
+            events if isinstance(events, Mapping) else dict.fromkeys(events, None)
+        )
         ret = {}
 
         for evt_name, doc in evt_dict.items():