(#) Modifier factory functions should return Modifier !!! WARNING: Modifier factory functions should return Modifier This is a warning. Id : `ModifierFactoryReturnType` Summary : Modifier factory functions should return Modifier Severity : Warning Category : Correctness Platform : Any Vendor : Jetpack Compose Identifier : androidx.compose.ui Feedback : https://issuetracker.google.com/issues/new?component=612128 Min : Lint 7.0 Compiled : Lint 8.0 and 8.1 Artifact : [androidx.compose.ui:ui-android](androidx_compose_ui_ui-android.md.html) 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/ui/ui-lint/src/main/java/androidx/compose/ui/lint/ModifierDeclarationDetector.kt) Tests : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/ui/ui-lint/src/test/java/androidx/compose/ui/lint/ModifierDeclarationDetectorTest.kt) Copyright Year : 2020 Modifier factory functions should return Modifier as their type, and not a subtype of Modifier (such as Modifier.Element). (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/androidx/compose/ui/foo/TestModifier.kt:8:Warning: Modifier factory functions should have a return type of Modifier [ModifierFactoryReturnType] fun Modifier.fooModifier(): Modifier.Element { ----------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/androidx/compose/ui/foo/TestModifier.kt`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers package androidx.compose.ui.foo import androidx.compose.ui.Modifier object TestModifier : Modifier.Element fun Modifier.fooModifier(): Modifier.Element { return this.then(TestModifier) } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/ui/ui-lint/src/test/java/androidx/compose/ui/lint/ModifierDeclarationDetectorTest.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, `ModifierDeclarationDetector.functionReturnsModifierElement`. 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.ui:ui-android:1.7.0-alpha01") // build.gradle implementation 'androidx.compose.ui:ui-android:1.7.0-alpha01' // build.gradle.kts with version catalogs: implementation(libs.ui-android) # libs.versions.toml [versions] ui-android = "1.7.0-alpha01" [libraries] ui-android = { module = "androidx.compose.ui:ui-android", version.ref = "ui-android" } ``` 1.7.0-alpha01 is the version this documentation was generated from; there may be newer versions available. [Additional details about androidx.compose.ui:ui-android](androidx_compose_ui_ui-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("ModifierFactoryReturnType") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("ModifierFactoryReturnType") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection ModifierFactoryReturnType 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="ModifierFactoryReturnType" 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 'ModifierFactoryReturnType' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore ModifierFactoryReturnType ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).