IssueTracker

Change from exception class to a third LoadResult.Invalid return type within LoadResult class in PagingSource.

Note that it is binary compatible but source-incompatible.

Project: platform/frameworks/support
Branch: androidx-main

commit 6bd2347ff259c28b34789c8569b7a298d2a8fd8d
Author: Clara Fok <clarafok@google.com>
Date:   Fri Jul 09 12:53:22 2021

    Implement Invalid return type in PagingSource
   
    Added third return type for LoadResult sealed class in PagingSource. It
    was added as a support feature to handle race scenarios between data loads
    and database invalidations, such as if Room's InvalidationTracker does
    not propagate invalidation signal to the PagingSource in time and the
    PagingSource continues querying an updated database. This can result in
    data being loaded onto a stale PageFetcherSnapshot causing duplicated or
    missing data. Related bug regarding race scenario in Room b/191806126.
   
    For example, if data was deleted and items shifted positions,
    positionally-keyed paging sources can end up loading duplicated items.
   
    Paging handles this return type by discarding the loaded data and
    invalidating the paging source. This will trigger a new paging source to
    be generated. This return type is also supported for Paging2 APIs
    leveraging PagingSource such as LivePagedList and RxPagedList.
   
    Aside from handling invalid data due to races, this return type can be
    leveraged in general where the database or network returns potentially
    invalid or stale data that needs to be discarded.
   
    Bug: 192013267
    Test: ./gradlew :paging:paging-common:test
    Relnote: "A third LoadResult return type LoadResult.Invalid is added to
        PagingSource. When a PagingSource.load returns
        LoadResult.Invalid, paging will discard the loaded data and
        invalidate the PagingSource. This return type is designed to
        handle potentially invalid or stale data that can be returned
        from the database or network.
   
        For example, if the underlying database gets written into but
        the PagingSource does not invalidate in time, it may return
        inconsistent results if its implementation depends on the
        immutability of the backing dataset it loads from (e.g., LIMIT
        OFFSET style db implementations). In this scenario, it is
        recommended to check for invalidation after loading and to
        return LoadResult.Invalid, which causes Paging to discard any
        pending or future load requests to this PagingSource and
        invalidate it.
   
        This return type is also supported by Paging2 API that leverages
        LivePagedList or RxPagedList. When using a PagingSource with
        Paging2's PagedList APIs, the PagedList is immediately detached,
        stopping further attempts to load data on this PagedList and
        triggers invalidation on the PagingSource.
   
        LoadResult is a sealed class, which means this is a
        source-incomptabile change such that use cases directly using
        PagingSource.load results will have to handle LoadResult.Invalid
        at compile time. For example, Kotlin users leveraging
        exhaustive-when to check return type will have to add a check
        for Invalid type."
   
    Change-Id: Id6bd3f2544f1ba97a95a0d590353438a95fedf2a

M       paging/common/api/current.txt
M       paging/common/api/public_plus_experimental_current.txt
M       paging/common/api/restricted_current.txt
M       paging/common/src/main/kotlin/androidx/paging/PageFetcherSnapshot.kt
M       paging/common/src/main/kotlin/androidx/paging/PagedList.kt
M       paging/common/src/main/kotlin/androidx/paging/PagingSource.kt
M       paging/common/src/test/kotlin/androidx/paging/PageFetcherSnapshotTest.kt
M       paging/common/src/test/kotlin/androidx/paging/PageFetcherTest.kt
M       paging/common/src/test/kotlin/androidx/paging/PagedListTest.kt
M       paging/common/src/test/kotlin/androidx/paging/PagingDataDifferTest.kt
M       paging/common/src/test/kotlin/androidx/paging/PagingSourceTest.kt
M       paging/integration-tests/testapp/src/main/java/androidx/paging/integration/testapp/v3room/V3RemoteMediator.kt
M       paging/integration-tests/testapp/src/main/java/androidx/paging/integration/testapp/v3room/V3RoomViewModel.kt

https://android-review.googlesource.com/1747297

Project: platform/frameworks/support
Branch: androidx-main

commit 24ac03f503425f05acfc9c2a1627cf179ab8de16
Author: Clara Fok <clarafok@google.com>
Date:   Mon Jul 12 10:47:27 2021

    Add LoadResult.Invalid support for Paging2
   
    This change adds LoadResult.Invalid support for Paging2 leveraging
    PagingSource, such as LivePagedList and RxPagedList.
   
    In the event of a PagingSource returning LoadResult.Invalid to its
    PagedList, paging will detach the PagedList to stop attempts to load
    on this PagedList and invalidate the PagingSource.
   
    If no initial page is provided to PagedList.Builder and the initial
    load fails with a LoadResult.Invalid, an IllegalStateException
    will be thrown. To use a PagingSource that supports invalidation, use a
    PagedList builder that accepts a factory method for PagingSource or
    DataSource.Factory such as LivePagedList.
   
    Bug: 192013267
    Test: ./gradlew :paging:paging-common:test
    Test: ./gradlew :paging:paging-runtime:cC
    Test: ./gradlew :paging:paging-rxjava2:test
    Test: ./gradlew :paging:paging-rxjava3:test
    Change-Id: I97de7e67cc5fe01b2c5c5a8e13bd1926c5ca2cde

M       paging/common/src/main/kotlin/androidx/paging/LegacyPageFetcher.kt
M       paging/common/src/test/kotlin/androidx/paging/ContiguousPagedListTest.kt
M       paging/common/src/test/kotlin/androidx/paging/LegacyPageFetcherTest.kt
M       paging/runtime/src/androidTest/java/androidx/paging/LivePagedListBuilderTest.kt
M       paging/runtime/src/androidTest/java/androidx/paging/LivePagedListTest.kt
M       paging/runtime/src/main/java/androidx/paging/LivePagedList.kt
M       paging/rxjava2/build.gradle
M       paging/rxjava2/src/main/java/androidx/paging/RxPagedListBuilder.kt
M       paging/rxjava2/src/test/java/androidx/paging/RxPagedListBuilderTest.kt
M       paging/rxjava3/build.gradle
M       paging/rxjava3/src/main/java/androidx/paging/rxjava3/RxPagedListBuilder.kt
M       paging/rxjava3/src/test/java/androidx/paging/RxPagedListBuilderTest.kt

https://android-review.googlesource.com/1758714