(#) NoOp Code !!! WARNING: NoOp Code This is a warning. Id : `NoOp` Summary : NoOp Code Note : **This issue is disabled by default**; use `--enable NoOp` Severity : Warning Category : Correctness Platform : Any Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Since : 8.1.0 (July 2023) 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/NoOpDetector.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/NoOpDetectorTest.kt) This check looks for code which looks like it's a no-op -- usually leftover expressions from interactive debugging, but in some cases bugs where you had intended to do something with the expression such as assign it to a field. (##) Options You can configure this lint checks using the following options: (###) pure-getters Whether to assume methods with getter-names have no side effects. Getter methods (where names start with `get` or `is`, and have non-void return types, and no arguments) should not have side effects. With this option turned on, lint will assume that is the case and will list any getter calls whose results are ignored as suspicious code. Default is false. Example `lint.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <lint> <issue id="NoOp"> <option name="pure-getters" value="false" /> </issue> </lint> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/Test.kt:3:Warning: This reference is unused: s === o [NoOp] s === o // ERROR 1 ------- src/Test.kt:4:Warning: This call result is unused: toString [NoOp] o.toString() // ERROR 2 ------------ src/Test.kt:5:Warning: This reference is unused: length [NoOp] s.length // ERROR 3 ------ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/Test.kt`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers class Test { fun test(s: String, o: Any) { s === o // ERROR 1 o.toString() // ERROR 2 s.length // ERROR 3 } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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/NoOpDetectorTest.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("NoOp") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("NoOp") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection NoOp 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="NoOp" 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 'NoOp' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore NoOp ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).