[meta] Reorganize Components so they are testable in isolation

Immediately postponed on #2943842: Allow component namespaces to be autoloaded independently while we make sure the component namespaces work.

@dawehner: Currently, the requirements and version constraints in each of the components' composer.json file is at best a guess, because it's hard to test.

There's this issue which will never be fixed because the solution seems like its too complex to review: #2876669-40: Fix dependency version requirement declarations in components

That solution is complex because it has to create a whole other testing system just for the components. Having the tests local to the components would make it easier to understand what's going on in that sort of issue.

We can't make this move until #2661542: Isolate Drupal\Tests\Component\Plugin\DefaultFactoryTest from core test module is in.

@alexpott: I'm not sure we need to do some of that. We'll definitely need to change TESTING.txt to whatever solution we arrive at.

We should also change TestDiscovery to use the test suites, and then also discover WTB tests.

Here's a patch that adds a testsuite called 'component'. It's governed by ComponentTestSuite.

The patch moves the Uuid test to the component directory.

You can do this:

$ ./vendor/bin/phpunit -c core --testsuite component --group Uuid

And you can also do this:

$ cd core/lib/Drupal/Component/Uuid/
$ ../../../../../vendor/bin/phpunit .

:-)

This patch also automatically adds the component testsuite to the unit testsuite, so whenever you say --testsuite unit you'll also run component. This is OK since all component tests must be unit tests, and they should fail anyway if they aren't.

$ ./vendor/bin/phpunit -c core/ --testsuite unit --group Uuid
PHPUnit 4.8.36 by Sebastian Bergmann and contributors.

Testing 
.......

Time: 14.27 seconds, Memory: 66.00MB

OK (7 tests, 7 assertions)

Where this doesn't help us is run-tests.sh:

$ php ./core/scripts/run-tests.sh --types PHPUnit-Unit Uuid
  ERROR: Test group not found: Uuid

That's because run-tests.sh uses TestDiscovery, which is above my pay grade to maintain at this point in time and space on this postponed issue.

Having them run as part of Unit makes sense because it'll limit the need for changes to testbot.

Well, except that run-tests.sh doesn't use test suites. It's a completely different discovery system. So we still have to make TestDiscovery either pay attention to the test suite classes, or have it do its own version of discovering tests in the components.

At this point I give a shoutout to #2863055-36: Move TestDiscovery out of simpletest module, minimize dependencies. :-)

Contemplating #2849669-51: Fix \Drupal\Component\Utility\Unicode() because of the Symfony mbstring polyfill and this issue....

The problem is that if we move the tests to where the components are, we end up with tests in our source.

So the solution is something like this:

core/
  lib/
  tests/
components/
  lib/
  tests/

We could also split them out into individual directories, something like:

components/
  Plugin/
    composer.json
    lib/
    tests/

This would involve restructuring the subtree split, and changing some paths in composer merges. Also probably adding another test suite to phpunit called components.

Ok, checking it out on the Uuid component.

• Add exclude-from-classmap to the composer.json file.
• Add autoload-dev to the composer.json file.
• Add a Tests directory with a test in it.
• $ cd core/lib/Drupal/Component/Uuid
• $ composer validate
• $ composer dumpautoload --no-dev
• Poke around in the generated vendor directory and see what's autoloadable.

The thing we verify here is that Tests is excluded from the classmap, but we never declared a classmap, so it kind of doesn't matter in that regard. When we say composer dumpautoload -o the test file is excluded from the map, even if it's in the autoload-dev PSR-4 list.

Maybe add a generic PHPUnit step to the testbot? #2837112-6: Add a test definition for a generic PHPUnit test run

It would give us drupalci.yml that would look like this:

      composer.annotation:
        working-directory: core/lib/Drupal/Component/Annotation
      phpunit.annotation:
        working-directory: core/lib/Drupal/Component/Annotation

...repeat for all the components.

We're still in technical debt mode on this because we don't have a way for run-tests.sh to run the tests outside of core/tests.

You can see how cumbersome it is now in #2876669: Fix dependency version requirement declarations in components, to the point that that issue is still outstanding.

Here's the travis CI version of it: https://github.com/paul-m/drupal_component_tester

I'm generally +1 on doing this for Composer stuff, in spirit. But it's also true that most of the Composer based tests are integration ones which build out a codebase from the git repo, to prove that it works. It might be that more strict unit tests could be moved to the composer/ directory, much as we'd do with components.