(#) Function type properties are not parcelable !!! ERROR: Function type properties are not parcelable This is an error. Id : `ParcelizeFunctionProperty` Summary : Function type properties are not parcelable Severity : Error Category : Correctness Platform : Any Vendor : slack Identifier : slack-lint Contact : https://github.com/slackhq/slack-lints Feedback : https://github.com/slackhq/slack-lints Min : Lint 8.7+ Compiled : Lint 8.7+ Artifact : [com.slack.lint:slack-lint-checks](com_slack_lint_slack-lint-checks.md.html) Since : 0.2.3 Affects : Kotlin and Java files and test sources Editing : This check runs on the fly in the IDE editor Implementation : [Source Code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/main/java/slack/lint/parcel/ParcelizeFunctionPropertyDetector.kt) Tests : [Source Code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/test/java/slack/lint/parcel/ParcelizeFunctionPropertyDetectorTest.kt) Copyright Year : 2023 While technically (and surprisingly) supported by Parcelize, function types should not be used in Parcelize classes. There are only limited conditions where it will work and it's usually a sign that you're modeling your data wrong. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/test/pkg/Example1.kt:12:Error: While technically (and surprisingly) supported by Parcelize, function types should not be used in Parcelize classes. There are only limited conditions where it will work and it's usually a sign that you're modeling your data wrong. [ParcelizeFunctionProperty] val functionType1: () -> String, ------------ src/test/pkg/Example1.kt:13:Error: While technically (and surprisingly) supported by Parcelize, function types should not be used in Parcelize classes. There are only limited conditions where it will work and it's usually a sign that you're modeling your data wrong. [ParcelizeFunctionProperty] val functionType2: (String) -> String, ------------------ src/test/pkg/Example1.kt:14:Error: While technically (and surprisingly) supported by Parcelize, function types should not be used in Parcelize classes. There are only limited conditions where it will work and it's usually a sign that you're modeling your data wrong. [ParcelizeFunctionProperty] val functionType3: String.() -> String, ------------------- src/test/pkg/Example1.kt:15:Error: While technically (and surprisingly) supported by Parcelize, function types should not be used in Parcelize classes. There are only limited conditions where it will work and it's usually a sign that you're modeling your data wrong. [ParcelizeFunctionProperty] val functionType4: () -> Unit, ---------- src/test/pkg/Example1.kt:16:Error: While technically (and surprisingly) supported by Parcelize, function types should not be used in Parcelize classes. There are only limited conditions where it will work and it's usually a sign that you're modeling your data wrong. [ParcelizeFunctionProperty] val functionType5: suspend () -> Unit, ------------------ src/test/pkg/Example1.kt:17:Error: While technically (and surprisingly) supported by Parcelize, function types should not be used in Parcelize classes. There are only limited conditions where it will work and it's usually a sign that you're modeling your data wrong. [ParcelizeFunctionProperty] val aliasedFunction: FunctionType, ------------ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/test/pkg/Example1.kt`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers package test.pkg import android.os.Parcelable import kotlinx.parcelize.Parcelize import kotlinx.parcelize.IgnoredOnParcel typealias FunctionType = () -> String @Parcelize class Example1( val foo: String, val functionType1: () -> String, val functionType2: (String) -> String, val functionType3: String.() -> String, val functionType4: () -> Unit, val functionType5: suspend () -> Unit, val aliasedFunction: FunctionType, val functionClass: FunctionClass, @IgnoredOnParcel val ignoredFunction: () -> Unit = {}, // This is allowed ) : Parcelable ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/test/java/slack/lint/parcel/ParcelizeFunctionPropertyDetectorTest.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, `ParcelizeFunctionPropertyDetector.simple`. To report a problem with this extracted sample, visit https://github.com/slackhq/slack-lints. (##) Including !!! This is not a built-in check. To include it, add the below dependency to your project. This lint check is included in the lint documentation, but the Android team may or may not agree with its recommendations. ``` // build.gradle.kts lintChecks("com.slack.lint:slack-lint-checks:0.9.0") // build.gradle lintChecks 'com.slack.lint:slack-lint-checks:0.9.0' // build.gradle.kts with version catalogs: lintChecks(libs.slack.lint.checks) # libs.versions.toml [versions] slack-lint-checks = "0.9.0" [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: slack-lint-checks = { module = "com.slack.lint:slack-lint-checks", version.ref = "slack-lint-checks" } ``` 0.9.0 is the version this documentation was generated from; there may be newer versions available. [Additional details about com.slack.lint:slack-lint-checks](com_slack_lint_slack-lint-checks.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("ParcelizeFunctionProperty") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("ParcelizeFunctionProperty") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection ParcelizeFunctionProperty 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="ParcelizeFunctionProperty" 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 'ParcelizeFunctionProperty' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore ParcelizeFunctionProperty ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).