Nullability Plugin

A Gradle plugin for verifying a Spring project's nullability at compile time. Gradle 8.x is supported.

Applying the Plugin

The plugin can then be applied to a project in the usual manner, as shown in the following example:

plugins {
	id "io.spring.nullability" version "<<version>>"
}

Configuring the Plugin

The plugin can be used without configuration. It will verify the nullability of all JavaCompile tasks whose name matches compile(\\d+)?Java.

A nullability extension is added by the plugin. The extension can be used to customize the versions of the dependencies that are used during verification.

nullability {
	errorProneVersion = <<custom-version>>
	nullAwayVersion = <<custom-version>>
}

Types of Nullability Checking

The plugin supports two types of nullability checking, main and tests. The former is applied by default to tasks whose name matches compile(\\d+)?Java. The latter is opt-in.

Checking using tests differs from main. It adds support for AssertJ's custom Contract annotation and enables NullAway's HandleTestAssertionLibraries option.

Configuring Nullability Checking

The plugin adds a nullability extension to the options of all JavaCompile tasks. The extension provides a single property, checking, that can be used to configure the type of null checking that is performed. It defaults to main for tasks whose name matches compile(\\d+)?Java. For all other JavaCompile tasks it defaults to disabled.

The following enables tests nullability checking for compileTestJava:

tasks.named("compileTestJava") {
	options.nullability.checking = "tests"
}