(#) BoxWithConstraints content should use the constraints provided via BoxWithConstraintsScope !!! ERROR: BoxWithConstraints content should use the constraints provided via BoxWithConstraintsScope This is an error. Id : `UnusedBoxWithConstraintsScope` Summary : BoxWithConstraints content should use the constraints provided via BoxWithConstraintsScope Severity : Error Category : Correctness Platform : Any Vendor : Jetpack Compose Identifier : androidx.compose.foundation Feedback : https://issuetracker.google.com/issues/new?component=612128 Min : Lint 8.0 and 8.1 Compiled : Lint 8.7+ Artifact : [androidx.compose.foundation:foundation-android](androidx_compose_foundation_foundation-android.md.html) Since : 1.6.0 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/foundation/foundation-lint/src/main/java/androidx/compose/foundation/lint/BoxWithConstraintsDetector.kt) Tests : [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/foundation/foundation-lint/src/test/java/androidx/compose/foundation/lint/BoxWithConstraintsDetectorTest.kt) Copyright Year : 2023 The `content` lambda in BoxWithConstraints has a scope which will include the incoming constraints. If this scope is ignored, then the cost of subcomposition is being wasted and this BoxWithConstraints should be replaced with a Box. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/foo/test.kt:9:Error: BoxWithConstraints scope is not used [UnusedBoxWithConstraintsScope] BoxWithConstraints { /**/ } -------- src/foo/test.kt:10:Error: BoxWithConstraints scope is not used [UnusedBoxWithConstraintsScope] BoxWithConstraints { foo } ------- src/foo/test.kt:11:Error: BoxWithConstraints scope is not used [UnusedBoxWithConstraintsScope] BoxWithConstraints(content = { /**/ }) -------- src/foo/test.kt:12:Error: BoxWithConstraints scope is not used [UnusedBoxWithConstraintsScope] BoxWithConstraints(propagateMinConstraints = false, content = { /**/ }) -------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/foo/test.kt`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers package foo import androidx.compose.foundation.layout.BoxWithConstraints import androidx.compose.runtime.Composable @Composable fun Test() { val foo = 123 BoxWithConstraints { /**/ } BoxWithConstraints { foo } BoxWithConstraints(content = { /**/ }) BoxWithConstraints(propagateMinConstraints = false, content = { /**/ }) } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/compose/foundation/foundation-lint/src/test/java/androidx/compose/foundation/lint/BoxWithConstraintsDetectorTest.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, `BoxWithConstraintsDetector.unreferencedConstraints`. 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.foundation:foundation-android:1.8.0-alpha07") // build.gradle implementation 'androidx.compose.foundation:foundation-android:1.8.0-alpha07' // build.gradle.kts with version catalogs: implementation(libs.foundation.android) # libs.versions.toml [versions] foundation-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: foundation-android = { module = "androidx.compose.foundation:foundation-android", version.ref = "foundation-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.foundation:foundation-lint:1.8.0-alpha07`. [Additional details about androidx.compose.foundation:foundation-android](androidx_compose_foundation_foundation-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("UnusedBoxWithConstraintsScope") fun method() { BoxWithConstraints(...) } ``` or ```java // Java @SuppressWarnings("UnusedBoxWithConstraintsScope") void method() { BoxWithConstraints(...); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection UnusedBoxWithConstraintsScope 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="UnusedBoxWithConstraintsScope" 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 'UnusedBoxWithConstraintsScope' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore UnusedBoxWithConstraintsScope ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).