rakshakhegde/custom-lints

Sample Lint Checks

This project shows how Android Studio 3 (beta 5 and later) handles packaging of lint rules.

Lint Check Jar Library

First, there's the lint check implementation itself. That's done in the "checks" project, which just applies the Gradle "java" plugin, and that project produces a jar. Note that the dependencies for the lint check project (other than its testing dependencies) must all be "compileOnly":

dependencies {
    compileOnly "com.android.tools.lint:lint-api:$lintVersion"
    compileOnly "com.android.tools.lint:lint-checks:$lintVersion"
	...

Lint Check AAR Library

Next, there's a separate Android library project, called "library". This library doesn't have any code on its own (though it could). However, in its build.gradle, it specifies this:

dependencies {
    lintChecks project(':checks')
}

This tells the Gradle plugin to take the output from the "checks" project and package that as a "lint.jar" payload inside this library's AAR file. When that's done, any other projects that depends on this library will automatically be using the lint checks.

App Modules

Note that you don't have to go through the extra "library indirection" if you have a lint check that you only want to apply to one or more app modules. You can simply include the lintChecks dependency as shown above there as well, and then lint will include these rules when analyzing the project.

Lint Version

The lint version of the libraries (specified in this project as the lintVersion variable in build.gradle) should be the same version that is used by the Gradle plugin.

If the Gradle plugin version is X.Y.Z, then the Lint library version is X+23.Y.Z.