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Support clearing the latest value in the LatestValueCache #426

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Support clearing the latest value in the LatestValueCache #426

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e16f3f0
Support clearing the latest value in the `LatestValueCache`
shsms Jun 16, 2025
9fcfc1a
Add tests for `LatestValueCache.clear()`
shsms Jun 16, 2025
fbbf48c
Update release notes
shsms Jun 16, 2025
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16 changes: 16 additions & 0 deletions src/frequenz/channels/_latest_value_cache.py
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Original file line number Diff line number Diff line change
Expand Up @@ -194,6 +194,22 @@ def has_value(self, key: HashableT | Sentinel = NO_KEY) -> bool:
return key in self._latest_value_by_key
return not isinstance(self._latest_value, Sentinel)

def clear(self, key: HashableT | Sentinel = NO_KEY) -> None:
"""Clear the latest value or the latest value for a specific key.

If `key` is provided, it clears the latest value for that key. If no key is
provided, it clears the latest value received overall.

Args:
key: An optional key to clear the latest value for that key. If not
provided, it clears the latest value received overall.
"""
if not isinstance(key, Sentinel):
_ = self._latest_value_by_key.pop(key, None)
return

self._latest_value = NO_VALUE_RECEIVED

Comment on lines +197 to +212
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@ela-kotulska-frequenz ela-kotulska-frequenz Jun 16, 2025 •
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Why call clear() doesn't remove all keys and values in self._latest_value_by_key ?
Or shouldn't you remove _latest_value_by_key[self._key(self._latest_value)]], too?

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@shsms shsms Jun 16, 2025

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oh damn, because my usecase didn't need clearing all keys. I wonder if we should change the API slightly to keep the option open for a "clear everything" in the future.

any opinions @llucax ?

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@shsms shsms Jun 16, 2025

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Another option is to make the key parameter required, so that I can make progress and we can decide how to generalise later.

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@llucax llucax Jun 16, 2025

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Some options I can think of:

  1. clear_all(), clear() but it is true that clear() with no key looks ambiguous
  2. clear_all(), clear_key() maybe is more clear that without a key it clears the no-key?

I'm starting to find the use case for a "global" key a bit weird. I guess we need to support it for backwards compatibility, otherwise maybe we should always require a key and let the user use something like None if they don't want one? Not sure.

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@shsms shsms Jun 16, 2025

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We haven't released it. I can actually pull out all the new stuff into experimental.GroupingLatestValueCache that doesn't have a global mode.

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@shsms shsms Jun 16, 2025

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Done here: #428

async def _run(self) -> None:
async for value in self._receiver:
self._latest_value = value
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