(#) Missing `add` call in `buildList` !!! WARNING: Missing `add` call in `buildList` This is a warning. Id : `BuildListAdds` Summary : Missing `add` call in `buildList` Severity : Warning Category : Correctness Platform : Any Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Since : 8.4.0 (April 2024) Affects : Kotlin and Java files Editing : This check runs on the fly in the IDE editor Implementation : [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/BuildListDetector.kt) Tests : [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/BuildListDetectorTest.kt) The `buildList { }` standard library function is a convenient way to build lists, but you need to actually call `add` on the items. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/Cubic.kt:4:Warning: No add calls within buildList lambda; this is usually a mistake [BuildListAdds] return buildList { // ERROR --------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/Cubic.kt`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers class Cubic(id: Int) val _morphMatch = listOf(1) fun asCubics_broken(progress: Float): List { return buildList { // ERROR for (i in _morphMatch.indices) { Cubic(i) // ERROR: Should have been wrapped in an add call. } } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/BuildListDetectorTest.kt) for the unit tests for this check to see additional scenarios. (##) 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("BuildListAdds") fun method() { buildList(...) } ``` or ```java // Java @SuppressWarnings("BuildListAdds") void method() { buildList(...); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection BuildListAdds 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="BuildListAdds" 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 'BuildListAdds' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore BuildListAdds ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).