(#) StateFlow.value should not be called within composition !!! ERROR: StateFlow.value should not be called within composition This is an error. Id : `StateFlowValueCalledInComposition` Summary : StateFlow.value should not be called within composition Severity : Error Category : Correctness Platform : Any Vendor : Jetpack Compose Identifier : androidx.compose.runtime Feedback : https://issuetracker.google.com/issues/new?component=612128 Min : Lint 8.0 and 8.1 Compiled : Lint 8.0 and 8.1 Artifact : [androidx.compose.runtime:runtime-android](androidx_compose_runtime_runtime-android.md.html) Since : 1.5.0 Affects : Kotlin and Java files and test sources Editing : This check runs on the fly in the IDE editor Implementation : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/runtime/runtime-lint/src/main/java/androidx/compose/runtime/lint/ComposableStateFlowValueDetector.kt) Tests : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/runtime/runtime-lint/src/test/java/androidx/compose/runtime/lint/ComposableStateFlowValueDetectorTest.kt) Copyright Year : 2021 Calling StateFlow.value within composition will not observe changes to the StateFlow, so changes might not be reflected within the composition. Instead you should use stateFlow.collectAsState() to observe changes to the StateFlow, and recompose when it changes. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/androidx/compose/runtime/foo/TestFlow.kt:20:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] testFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:24:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] stateFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:25:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] testFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:29:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] stateFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:30:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] testFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:39:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] stateFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:40:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] testFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:43:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] stateFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:44:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] testFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:50:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] stateFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:51:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] testFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:55:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] stateFlow.value ----- src/androidx/compose/runtime/foo/TestFlow.kt:56:Error: StateFlow.value should not be called within composition [StateFlowValueCalledInComposition] testFlow.value ----- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/androidx/compose/runtime/foo/TestFlow.kt`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers package androidx.compose.runtime.foo import androidx.compose.runtime.Composable import kotlinx.coroutines.flow.* val stateFlow: StateFlow = object : StateFlow { override val value = true } class TestFlow : StateFlow { override val value = true } val testFlow = TestFlow() @Composable fun Test() { stateFlow.value testFlow.value } val lambda = @Composable { stateFlow.value testFlow.value } val lambda2: @Composable () -> Unit = { stateFlow.value testFlow.value } @Composable fun LambdaParameter(content: @Composable () -> Unit) {} @Composable fun Test2() { LambdaParameter(content = { stateFlow.value testFlow.value }) LambdaParameter { stateFlow.value testFlow.value } } fun test3() { val localLambda1 = @Composable { stateFlow.value testFlow.value } val localLambda2: @Composable () -> Unit = { stateFlow.value testFlow.value } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/runtime/runtime-lint/src/test/java/androidx/compose/runtime/lint/ComposableStateFlowValueDetectorTest.kt) for the unit tests for this check to see additional scenarios. The above example was automatically extracted from the first unit test found for this lint check, `ComposableStateFlowValueDetector.errors`. To report a problem with this extracted sample, visit https://issuetracker.google.com/issues/new?component=612128. (##) Including !!! This is not a built-in check. To include it, add the below dependency to your project. ``` // build.gradle.kts implementation("androidx.compose.runtime:runtime-android:1.8.0-alpha07") // build.gradle implementation 'androidx.compose.runtime:runtime-android:1.8.0-alpha07' // build.gradle.kts with version catalogs: implementation(libs.runtime.android) # libs.versions.toml [versions] runtime-android = "1.8.0-alpha07" [libraries] # For clarity and text wrapping purposes the following declaration is # shown split up across lines, but in TOML it needs to be on a single # line (see https://github.com/toml-lang/toml/issues/516) so adjust # when pasting into libs.versions.toml: runtime-android = { module = "androidx.compose.runtime:runtime-android", version.ref = "runtime-android" } ``` 1.8.0-alpha07 is the version this documentation was generated from; there may be newer versions available. NOTE: These lint checks are **also** made available separate from the main library. You can also use `androidx.compose.runtime:runtime-lint:1.8.0-alpha07`. [Additional details about androidx.compose.runtime:runtime-android](androidx_compose_runtime_runtime-android.md.html). (##) Suppressing You can suppress false positives using one of the following mechanisms: * Using a suppression annotation like this on the enclosing element: ```kt // Kotlin @Suppress("StateFlowValueCalledInComposition") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("StateFlowValueCalledInComposition") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection StateFlowValueCalledInComposition problematicStatement() ``` * Using a special `lint.xml` file in the source tree which turns off the check in that folder and any sub folder. A simple file might look like this: ```xml <?xml version="1.0" encoding="UTF-8"?> <lint> <issue id="StateFlowValueCalledInComposition" severity="ignore" /> </lint> ``` Instead of `ignore` you can also change the severity here, for example from `error` to `warning`. You can find additional documentation on how to filter issues by path, regular expression and so on [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html). * In Gradle projects, using the DSL syntax to configure lint. For example, you can use something like ```gradle lintOptions { disable 'StateFlowValueCalledInComposition' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore StateFlowValueCalledInComposition ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).