Temporal coupling in InstallComposerDevDependencyTaskExecutor

[rjkip]

Originally submitted by @rpkamp:

The InstallComposerDevDependencyTaskExecutor has a temporal coupling problem with the arePrerequisitesMet and execute methods. Namely, if you call execute without calling arePrerequisitesMet first, the tool will blow up because the class property composerProject is not set yet.

Although this is not a big problem because the class is only called in a fixed manner from outside, it would be nice to rid of this temporal coupling by somehow preventing execute from running if arePrerequisitesMet hasn't run yet, and maybe also when arePrerequisitesMet did run but the prerequisites were not met.

A relatively easy way to do this would be something like

private $arePrerequisitesMet = false;

public function arePrerequisitesMet(...)
{
    // some checking here
    $this->arePrerequisitesMet = true;
}

public function execute()
{
    if (!$this->arePrerequisitesMet) {
        throw new RuntimeException(
            sprintf(
                'Either the prerequisites for "%s" have not been checked, or they have not been met.',
                get_class($this)
            )
        );
    }
    // execute code
}

[rjkip]

I must note that it's currently by design; consumers of the Executor API must take this temporal coupling into account. This design was put in place to keep Executors simple and it wasn't a conscious decision to incur technical debt to further the project. Not sure I like putting the suggested checks in place in all Executors. I'm still open to being convinced otherwise or to other solutions, though 😉