feat(signal-slice): optimize subscription management

[endlacer]

Problem

Calling a function-form actionSource (e.g. increaseAge: (state, $) => $.pipe(...)) with a plain, non-Observable value created a brand-new subscription to the action's already-connected, shared pipeline on every call, in addition to the one permanent subscription connect() makes once at slice-creation time. Each of these extra subscriptions was wired to takeUntilDestroyed(destroyRef) and only released when the owning injector was destroyed — never between calls — so live subscriptions accumulated without bound for the lifetime of the slice.

Root cause

The offending .subscribe() call in addReducerProperties used to have real handlers: it fed an effectTrigger Subject that powered the experimental actionEffects API (added in #154). When actionEffects was removed in #361, the next/error handlers were stripped out but the bare .subscribe() call was left behind - a leftover with nothing listening, serving no purpose beyond registering a new teardown per call.

Fix

Deleted the dead resubscription block and the now-unused observableFromActionSource parameter it depended on. State updates are unaffected - they were already handled entirely by the permanent connect(state, sharedObservable) subscription made once at slice creation.

Testing

• Added a regression test asserting that repeated calls to a plain-value action don't register additional DestroyRef.onDestroy teardowns beyond the one made at slice creation.
• Verified the test fails against the old code (i.e. it actually catches the leak) and passes with the fix.
• Full signal-slice suite (28 tests) and ngxtension lint pass.

No public API changes.

[nx-cloud]

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☁️ Nx Cloud last updated this comment at 2026-07-08 06:47:34 UTC

[gemini-code-assist]

Code Review

This pull request optimizes subscription handling in signalSlice by removing redundant subscriptions to action sources and preventing multiple permanent subscription teardowns when actions are called with plain values. A unit test has been added to verify this behavior. The feedback suggests further cleanup by removing the now-redundant share() operator on the observable and restoring the Jest spy at the end of the new test to prevent mock pollution.

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[gemini-code-assist]

Since sharedObservable is no longer passed to addReducerProperties, it is only subscribed to once by connect(state, sharedObservable) at line 204. This makes the share() operator on line 203 redundant. You can clean this up by removing const sharedObservable = observable.pipe(share()); and passing observable directly to connect(state, observable).

[gemini-code-assist]

It is a good practice to restore Jest spies at the end of the test to prevent potential mock pollution or side effects in other tests within the same suite.

				expect(onDestroySpy.mock.calls.length).toEqual(baseline);
				onDestroySpy.mockRestore();