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Matthew Hodgson
d8a2ac75a8
* Fix CurrentValuePublisher.map dropping updates when the mapped publisher is chained inline
The eager implementation bridged through a second CurrentValueSubject fed by
a sink whose AnyCancellable was stored on the returned struct. Combine
consumes publisher structs when building a subscription, so chaining the
mapped publisher inline (e.g. `publisher.map { … }.removeDuplicates(…)
.sink { … }`, as RoomScreenViewModel and RoomDetailsScreenViewModel do for
knock requests) dropped the only copy holding that cancellable: the feeding
sink was cancelled and subscribers only ever received the initial value.
In practice this meant a room admin viewing a knockable room never saw the
"wants to join" banner (or a live "Requests to join" badge) for a knock
arriving while the room was open — it only appeared when the knock predated
opening the room. Caught by a live cross-client knocking test; the
double-execution of the transform at subscription time (eager transform +
current-value replay) was the giveaway.
Make map lazy instead: keep the transformed AnyPublisher and a value
provider, so subscribers attach straight through to the source subject (which
replays its current value itself) and no keep-alive is needed. Adds a
regression test chaining a mapped publisher inline.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
* swiftformat
* better docs
---------
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Mauro Romito <mauro.romito@element.io>
49 lines
1.6 KiB
Swift
49 lines
1.6 KiB
Swift
//
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// Copyright 2026 Element Creations Ltd.
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//
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// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
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// Please see LICENSE files in the repository root for full details.
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//
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import Combine
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@testable import ElementX
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import Testing
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struct CurrentValuePublisherTests {
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@Test
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func publisherReplaysCurrentValueAndDeliversSubsequentOnes() {
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let subject = CurrentValueSubject<Int, Never>(1)
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var received = [Int]()
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let cancellable = subject.asCurrentValuePublisher().sink { received.append($0) }
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subject.send(2)
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subject.send(3)
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#expect(received == [1, 2, 3])
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cancellable.cancel()
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}
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@Test
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func mappedPublisherChainedInlineDeliversSubsequentValues() {
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let subject = CurrentValueSubject<Int, Never>(1)
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var received = [Int]()
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// The mapped publisher is intentionally chained without being stored: the struct is
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// discarded mid-chain, which used to cancel an eager map's subscription and stop updates.
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let cancellable = subject.asCurrentValuePublisher()
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.map { $0 * 2 }
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.removeDuplicates()
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.sink { received.append($0) }
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subject.send(2)
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subject.send(3)
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#expect(received == [2, 4, 6])
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cancellable.cancel()
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}
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@Test
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func mappedPublisherValueStaysCurrent() {
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let subject = CurrentValueSubject<Int, Never>(1)
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let mapped = subject.asCurrentValuePublisher().map { $0 * 2 }
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#expect(mapped.value == 2)
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subject.send(5)
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#expect(mapped.value == 10)
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}
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}
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