(#) `Saver` objects should be passed to the saver parameter, not the vararg `inputs` parameter !!! ERROR: `Saver` objects should be passed to the saver parameter, not the vararg `inputs` parameter This is an error. Id : `RememberSaveableSaverParameter` Summary : `Saver` objects should be passed to the saver parameter, not the vararg `inputs` parameter Severity : Error Category : Correctness Platform : Any Vendor : Jetpack Compose Identifier : androidx.compose.runtime.saveable Feedback : https://issuetracker.google.com/issues/new?component=612128 Min : Lint 8.0 and 8.1 Compiled : Lint 8.7+ Artifact : [androidx.compose.runtime:runtime-saveable-android](androidx_compose_runtime_runtime-saveable-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-saveable-lint/src/main/java/androidx/compose/runtime/saveable/lint/RememberSaveableDetector.kt) Tests : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/runtime/runtime-saveable-lint/src/test/java/androidx/compose/runtime/saveable/lint/RememberSaveableDetectorTest.kt) Copyright Year : 2021 The first parameter to `rememberSaveable` is a vararg parameter for inputs that when changed will cause the state to reset. Passing a `Saver` object to this parameter is an error, as the intention is to pass the `Saver` object to the saver parameter. Since the saver parameter is not the first parameter, it must be explicitly named. !!! Tip This lint check has an associated quickfix available in the IDE. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/test/Foo.kt:15:Error: Passing Saver instance to vararg inputs [RememberSaveableSaverParameter] val foo = rememberSaveable(FooSaver) { Foo() } -------- src/test/Foo.kt:16:Error: Passing Saver instance to vararg inputs [RememberSaveableSaverParameter] val mutableStateFoo = rememberSaveable(FooSaver) { mutableStateOf(Foo()) } -------- src/test/Foo.kt:17:Error: Passing Saver instance to vararg inputs [RememberSaveableSaverParameter] val foo2 = rememberSaveable(FooSaver2()) { Foo() } ----------- src/test/Foo.kt:18:Error: Passing Saver instance to vararg inputs [RememberSaveableSaverParameter] val mutableStateFoo2 = rememberSaveable(FooSaver2()) { mutableStateOf(Foo()) } ----------- src/test/Foo.kt:19:Error: Passing Saver instance to vararg inputs [RememberSaveableSaverParameter] val foo3 = rememberSaveable(fooSaver3) { Foo() } --------- src/test/Foo.kt:20:Error: Passing Saver instance to vararg inputs [RememberSaveableSaverParameter] val mutableStateFoo3 = rememberSaveable(fooSaver3) { mutableStateOf(Foo()) } --------- src/test/Foo.kt:21:Error: Passing Saver instance to vararg inputs [RememberSaveableSaverParameter] val foo4 = rememberSaveable(fooSaver4) { Foo() } --------- src/test/Foo.kt:22:Error: Passing Saver instance to vararg inputs [RememberSaveableSaverParameter] val mutableStateFoo4 = rememberSaveable(fooSaver4) { mutableStateOf(Foo()) } --------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/test/Foo.kt`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers package test import androidx.compose.runtime.* import androidx.compose.runtime.saveable.* class Foo object FooSaver : Saver class FooSaver2 : Saver val fooSaver3 = object : Saver {} val fooSaver4 = FooSaver2() @Composable fun Test() { val foo = rememberSaveable(FooSaver) { Foo() } val mutableStateFoo = rememberSaveable(FooSaver) { mutableStateOf(Foo()) } val foo2 = rememberSaveable(FooSaver2()) { Foo() } val mutableStateFoo2 = rememberSaveable(FooSaver2()) { mutableStateOf(Foo()) } val foo3 = rememberSaveable(fooSaver3) { Foo() } val mutableStateFoo3 = rememberSaveable(fooSaver3) { mutableStateOf(Foo()) } val foo4 = rememberSaveable(fooSaver4) { Foo() } val mutableStateFoo4 = rememberSaveable(fooSaver4) { mutableStateOf(Foo()) } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/runtime/runtime-saveable-lint/src/test/java/androidx/compose/runtime/saveable/lint/RememberSaveableDetectorTest.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, `RememberSaveableDetector.saverPassedToVarargs`. 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-saveable-android:1.9.0-alpha01") // build.gradle implementation 'androidx.compose.runtime:runtime-saveable-android:1.9.0-alpha01' // build.gradle.kts with version catalogs: implementation(libs.runtime.saveable.android) # libs.versions.toml [versions] runtime-saveable-android = "1.9.0-alpha01" [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-saveable-android = { module = "androidx.compose.runtime:runtime-saveable-android", version.ref = "runtime-saveable-android" } ``` 1.9.0-alpha01 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-saveable-lint:1.9.0-alpha01`. [Additional details about androidx.compose.runtime:runtime-saveable-android](androidx_compose_runtime_runtime-saveable-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("RememberSaveableSaverParameter") fun method() { rememberSaveable(...) } ``` or ```java // Java @SuppressWarnings("RememberSaveableSaverParameter") void method() { rememberSaveable(...); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection RememberSaveableSaverParameter 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="RememberSaveableSaverParameter" 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 'RememberSaveableSaverParameter' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore RememberSaveableSaverParameter ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).