Gradle - Task

About

A build process execute a graph of tasks.

Task may just be:

• container (lifecycle task)
• or provided by plugin

Example

• In Gradle - Kotlin DSL

tasks.register("Hello") {
  println("Hello")
}

• execution with the wrapper of the project

gradlew Hello

Hello

Model

Tasks themselves consist of:

• Actions — pieces of work that do something, like copy files or compile source
• Inputs — values, files and directories that the actions use or operate on
• Outputs — files and directories that the actions modify or generate

A task should never call another task.

Tasks should define inputs and outputs to get the performance benefits of incremental build functionality.

Output

When declaring the outputs of a task, make sure that the directory for writing outputs is unique among all the tasks in your project.

Intermingling or overwriting output files produced by different tasks compromises up-to-date checking causing slower builds. In turn, these filesystem changes may prevent Gradle’s build cache from properly identifying and caching what would otherwise be cacheable tasks.

Management

Create

Task are provided by:

• the core api.
• or plugin

Built-in

Example for copy

task copy(type: Copy, group: "Custom", description: "Copies sources to the dest directory") {
    from "src"
    into "dest"
}

Register

Kotlin

tasks.register("logInfo") {
  logging.captureStandardOutput(LogLevel.INFO)
  doFirst {
    println("A task message which is logged at INFO level")
  }
}

Default

task echo(description: 'Default task') << {
    println 'Hello'
}
defaultTasks 'echo'

List

• In one project directory

gradlew tasks 
# or
gradlew tasks --all

• multi-project call from the root

gradle :services:webservice:tasks

Property

tasks.withType(JavaCompile) {
        options.encoding = 'UTF-8'
}

• Lookup

val testTask =  tasks.getByName<Test>("test");
testTask.failFast = true;

• Or declarative

tasks.test {
   failFast = true;
}

Execute

gradle -q taskName

where:

• -q stands for quiet

Exclude

• Specify a task to be excluded from execution.

gradle [-x|--exclude-task]

• Specify a task to be excluded dynamically. See How to skip a task if another task is executed in Gradle?

Cache

Ignore previously cached task results.

gradle --rerun-tasks

Help

gradlew help --task <task>

Disable

Run the builds with all task actions disabled.

gradle [-m|--dry-run]

Dependency

https://docs.gradle.org/current/userguide/tutorial_using_tasks.html#sec:task_dependencies

tasks.register("hello") {
    doLast {
        println("Hello world!")
    }
}
tasks.register("intro") {
    dependsOn("hello")
    doLast {
        println("I'm Gradle")
    }
}

Cache

See Gradle - Cache (.gradle)