Gradle Checker Framework Plugin

This plugin configures JavaCompile tasks to use the Checker Framework for pluggable type-checking.

Download

Add the following to your build.gradle file:

plugins {
    // Checker Framework pluggable type-checking
    id 'org.checkerframework' version '0.3.25'
}

apply plugin: 'org.checkerframework'

Configuration

Configuring which checkers to use

The checkerFramework.checkers property lists which checkers will be run.

For example:

checkerFramework {
  checkers = [
    'org.checkerframework.checker.nullness.NullnessChecker',
    'org.checkerframework.checker.units.UnitsChecker'
  ]
}

For a list of checkers, see the Checker Framework Manual.

Providing checker-specific options to the compiler

You can set the checkerFramework.extraJavacArgs property in order to pass additional options to the compiler when running a typechecker.

For example, to use a stub file:

checkerFramework {
  extraJavacArgs = [
    '-Werror',
    '-Astubs=/path/to/my/stub/file.astub'
  ]
}

Configuring third-party checkers

To use a third-party typechecker (i.e. one that is not distributed with the Checker Framework), add a dependency to the checkerFramework dependency configuration.

For example, to use the Glacier immutability checker:

dependencies {
  ...
  checkerFramework 'edu.cmu.cs.glacier:glacier:0.1'
}

Specifying a Checker Framework version

This plugin uses Checker Framework version 2.10.0 by default. Anytime you upgrade to a newer version of this plugin, it might use a different version of the Checker Framework.

If you wish to use a specific Checker Framework version, add text like the following to build.gradle, after apply plugin: 'org.checkerframework':

dependencies {
  compileOnly 'org.checkerframework:checker-qual:2.8.0'
  testCompileOnly 'org.checkerframework:checker-qual:2.8.0'
  checkerFramework 'org.checkerframework:checker:2.8.0'
  checkerFrameworkAnnotatedJDK 'org.checkerframework:jdk8:2.8.0'
}

You can also use a locally-built version of the Checker Framework:

// To use a locally-built Checker Framework, run gradle with "-PcfLocal".
if (project.hasProperty("cfLocal")) {
  def cfHome = String.valueOf(System.getenv("CHECKERFRAMEWORK"))
  dependencies {
    compileOnly files(cfHome + "/checker/dist/checker-qual.jar")
    testCompileOnly files(cfHome + "/checker/dist/checker-qual.jar")
    checkerFramework files(cfHome + "/checker/dist/checker.jar")
    checkerFrameworkAnnotatedJDK files(cfHome + "/checker/dist/jdk8.jar")
  }
}

Other options

By default, the plugin applies the selected checkers to all JavaCompile targets.

Here is how to prevent checkers from being applied to test targets:
```
checkerFramework {
  excludeTests = true
}
```
The check for test targets is entirely syntactic: this option will not apply the checkers to any task whose name includes "test", ignoring case.
If you encounter errors of the form zip file name too long when configuring your Gradle project, you can use the following code to skip this plugin's version check, which reads the manifest file of the version of the Checker Framework you are actually using:
```
checkerFramework {
  skipVersionCheck = true
}
```

Multi-project builds

By default, checkers are run on all subprojects of the project to which the plugin is applied.

In most projects with subprojects, the top-level project is not a Java project. You should not configure such a non-Java project. Instead, move all Checker Framework configuration (the checkerFramework block and any dependencies) into a subprojects block. For example:

subprojects { subproject ->
  checkerFramework {
    checkers = ['org.checkerframework.checker.index.IndexChecker']
  }
  dependencies {
    checkerFramework 'org.checkerframework:checker:2.10.0'
    implementation 'org.checkerframework:checker-qual:2.10.0'
  }
}

To not apply the plugin to all subprojects, set the applyToSubprojects flag to false:

checkerFramework {
  applyToSubprojects = false
}

Then, apply the plugin to the build.gradle in each subproject where you do want to run the checker.

Incompatibility with Error Prone

Error Prone uses the Checker Framework's dataflow analysis library. Unfortunately, Error Prone uses an old version of the library, so you cannot use both Error Prone and the current Checker Framework (because each one depends on a different version of the library).

You can resolve this via a switch that causes your build to use either Error Prone or the Checker Framework, but not both. Here is how do change the above instructions:

plugins {
  id "net.ltgt.errorprone-base" version "0.0.16" apply false
  // To do Checker Framework pluggable type-checking (and disable Error Prone), run:
  // ./gradlew compileJava -PuseCheckerFramework=true
  id 'org.checkerframework' version '0.3.25' apply false
}

if (!project.hasProperty("useCheckerFramework")) {
    ext.useCheckerFramework = "false"
}
if ("true".equals(project.ext.useCheckerFramework)) {
  apply plugin: 'org.checkerframework'
} else {
  apply plugin: 'net.ltgt.errorprone-base'
}


def checkerFrameworkVersion = "2.10.0"

dependencies {
  if ("true".equals(project.ext.useCheckerFramework)) {
    checkerFramework 'org.checkerframework:checker:' + checkerFrameworkVersion
    checkerFramework 'org.checkerframework:jdk8:' + checkerFrameworkVersion
    checkerFramework 'org.checkerframework:checker-qual:' + checkerFrameworkVersion
  } else {
    errorprone group: 'com.google.errorprone', name: 'error_prone_core', version: '2.3.3'
  }
}

if ("true".equals(project.ext.useCheckerFramework)) {
  checkerFramework {
    checkers = [
      'org.checkerframework.checker.interning.InterningChecker',
      'org.checkerframework.checker.signature.SignatureChecker'
    ]
  }
} else {
  // Configuration for the Error Prone linter.
  tasks.withType(JavaCompile).each { t ->
    if (!t.name.equals("compileTestInputJava") && !t.name.startsWith("checkTypes")) {
      t.toolChain ErrorProneToolChain.create(project)
      t.options.compilerArgs += [
        '-Xep:StringSplitter:OFF',
        '-Xep:ReferenceEquality:OFF' // use Interning Checker instead
      ]
    }
  }
}

Java 9+ compatibility

When using a Checker Framework version above 3.0.0 that is compatible with Java 9 and executing on a Java 8 JVM, this plugin will automatically substitute a Checker Framework-compatible Error Prone Java compiler version (from com.google.errorprone:javac). This is necessary because Checker Framework versions starting at 3.0.0 build on the Java 9 compiler.

When using a Checker Framework version above 3.0.0 and executing on a Java 9+ JVM, the host Java compiler is used.

Lombok compatibility

This plugin automatically interacts with the Lombok Gradle Plugin to delombok your source code before it is passed to the Checker Framework for typechecking. This plugin does not support any other use of Lombok.

Using a locally-built plugin

You can build the plugin locally rather than downloading it from Maven Central.

To build the plugin from source, run ./gradlew build.

If you want to use a locally-built version of the plugin, you can publish the plugin to your local Maven repository by running ./gradlew publish. In the build.gradle file for each project for which you want to use the locally-built plugin, make sure that mavenLocal() is the first entry in the repositories block within the buildscript block. A full example will look like this:

buildscript {
  repositories {
    mavenLocal()
  }

  dependencies {
    classpath 'gradle.plugin.org.checkerframework:checkerframework-gradle-plugin:0.3.25-SNAPSHOT'
  }
}

apply plugin: 'org.checkerframework'

Credits

This project started as a fork of a plugin built by jaredsburrows.

License

Copyright (C) 2017 Jared Burrows, 2019 Martin Kellogg

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

octylFractal / checkerframework-gradle-plugin