IllegalStateException thrown when change a MutableState value in the background: "Reading a state that was created after the snapshot was taken or in a snapshot that has not yet been applied" [166486000]

Fixed

Bug

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Description

ma...@gmail.com

created issue #1

Aug 26, 2020 09:19PM

Version of Gradle Plugin: 4.2.0-alpha07
Version of Gradle: 6.6
Version of Java: 1.8
OS: Android 10

Compose options:

composeOptions {
    kotlinCompilerVersion "1.4.0"
    kotlinCompilerExtensionVersion "0.1.0-dev17"
}

Updating a MutableState value in the backgroung, sometimes I get the following error:

java.lang.IllegalStateException: Reading a state that was created after the snapshot was taken or in a snapshot that has not yet been applied
        at androidx.compose.runtime.snapshots.SnapshotKt.readError(Snapshot.kt:1495)
        at androidx.compose.runtime.snapshots.SnapshotKt.current(Snapshot.kt:1654)
        at androidx.compose.runtime.SnapshotMutableState.setValue(MutableState.kt:499)
        at com.manueldidonna.redhex.inventory.FakeInventory.fetchItems(Test.kt:26)
        at com.manueldidonna.redhex.inventory.TestKt$TestSnapshotCrash$2$1$1.invokeSuspend(Test.kt:60)

Code to reproduce is attached. See @Composable TestSnapshotCrash() It's a simple layout with 3 Tabs and a LazyColumn. Changing the tab, a new list is created in the background and assigned to a mutablestate. That state is used in the lazycolumn. If you change the tab very quickly and many times, the crash should happen.

TestSnapshotCrash.kt

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Comments

so...@google.com <so...@google.com> Aug 27, 2020 10:00AM

Assigned to ch...@google.com.

ch...@google.com <ch...@google.com> #2Aug 27, 2020 11:07PM

I'll be happy to implement this

ch...@google.com <ch...@google.com> #3Aug 28, 2020 12:53AM

Thanks. Let us know when you have some API design (not looking for a doc, just commenting here is also fine, whichever is easier for you).

One tricky bit about this one is the "transactionality" of it.

e.g. we need to handle the case where we called onPopuplated but application crashed before onPopulated could succeed. We need to re-run it in the next run. We might do this by keeping a record in room_master_table (there might be a better option, this is the first thing that comes to my mind)

ch...@google.com <ch...@google.com> Aug 28, 2020 05:58PM

Reassigned to ad...@google.com.

ap...@google.com <ap...@google.com> #4Aug 29, 2020 12:30AM

Marked as fixed.

I looked around the code and I found out that actual copying of the database file is done in SQLiteCopyOpenHelper - getWritableDatabase() and getReadableDatabase() methods are calling verifyDatabaseFile() which does the copying under the hoods.

My idea is to:
1. Add RoomDatabase.Callback#onPopulated method
2. SQLiteCopyOpenHelper already has access to a list of callbacks (List<RoomDatabase.Callback>) through mDatabaseConfiguration.callbacks
3. Modify getWritableDatabase() and getReadableDatabase() so that after the file is copied I can iterate over those callbacks and call onPopulated. I would pass mDelegate.getWritableDatabase() and mDelegate.getReadableDatabase() as a parameter to onPopulated.
4. Add tests in DatabaseCallbackTest

I asked Danny about it and he said that I might need to temporarily open the DB with a vanilla open helper just to invoke onPopulated close it and then let Room re-open it through the normal path. Not sure how would I do that yet so I'm still reading and trying to get better understanding of the code.

This probably also doesn't take this "transactionality" thing into account so I need to look into it. I think I'll try to create some tests that will help me verify if it works or not.

I'm also wondering if there is a way to build the lib locally so I can test it on a sample project. Can I somehow publish it to local maven or something?

Issue 166486000