Can you explain the mechanism of task execution in the Gradle build system?

In Gradle, tasks are the main units of work that perform specific actions, such as compiling code, copying files, or running tests. Each task is described in the build script and has:

• A name
• Actions it performs
• Dependencies on other tasks

The task execution mechanism is based on lazy evaluation: tasks are not executed immediately during project configuration but only when the build is run if they are needed. Gradle constructs a dependency graph of tasks and executes them in the correct order.

An example of a simple task in Gradle (Groovy DSL):

task hello {
    doLast {
        println 'Hello, Gradle!'
    }
}

Here, doLast adds an action that will be executed when the hello task is run.

Gradle also supports typed tasks, which can be configured and extended. Tasks can have input and output parameters, which helps Gradle optimize the build by skipping tasks if their results haven't changed.