Add tests to enforce correct use of help_topic_link and help_route_link functions

Moving to active as ticket in #2 is closed.

Working on this. Looks like I can use Drupal\Tests\Core\Utility\LinkGeneratorTest for guidance.

Good idea 👍 looks that one is primary blocker

According to the IS, there are 3 objectives. The only thing missing from HelpTopicsSyntaxTest (as far as I could tell) was a check for use of url(). I happened to have a month-old pull of 10.1.x which had 2 core help topics that still used url() (i.e. {% set search_url = render_var(url('search.view')) %}) and my update to this test caught them. (It doesn't catch all of them at once, just the first one it finds. When that one is fixed, then it would catch the next failure.)

1. Both help_topic_link and help_route_link functions are being used for links and not the base Twig url() function.

- I added a string-match check in HelpTopicsSyntaxTest::verifyTopic() to see if url( was found. I didn't know how to explicitly check for use of a certain function in this testing framework. So I hope that string-match type of check will suffice here.
- I added a "bad topic" (core/modules/help_topics/tests/modules/help_topics_test/bad_help_topics/syntax/bad_help_topics.url_func_used.html.twig) that uses url()
- I added a case to HelpTopicsSyntaxTest::verifyBadTopic() that verifies that the new bad topic fails as expected.
- There is already a test topic (core/modules/help_topics/tests/modules/help_topics_test/help_topics/help_topics_test.test_urls.html.twig) that uses help_route_link() and help_topic_link() in various ways and tests them in HelpTopicsSyntaxTest::verifyTopic()

2. If help_route_link or help_topic_link is used, the text is translated.

- This appears to be covered already with HelpTopicsSyntaxTest::verifyTopic() as it checks core/modules/help_topics/tests/modules/help_topics_test/help_topics/help_topics_test.test_urls.html.twig

3. The syntax test includes "bad" examples to verify the tests are working, so there should also be "bad" examples added that violate those two test cases, to make sure the test is working properly.

- This appears to be covered already with HelpTopicsSyntaxTest::verifyTopic() as it checks core/modules/help_topics/tests/modules/help_topics_test/help_topics/help_topics_test.test_urls.html.twig

I'm also working on a unit test to cover HelpTwigExtension::getRouteLink() and HelpTwigExtension::getTopicLink() but I'm struggling. Maybe it's something we can add later and isn't necessary for this issue, as it isn't in the original scope. (I can open a follow-up issue if it seems like a good idea to others.)

Re-testing the patch as test failure looked like an infrastructure error and not an error from the patch.

It looks great and solves the issue but follow-up is required for twig functions, \Drupal\Tests\Core\Template\TwigExtensionTest::testFileUrl() could be used as example, I'm fine with follow-up

Re-reading #3090659-93: Make a way for help topics to generate links only if they work and are accessible I see that we have extensive functional testing coverage and the scope of the issue is to check all shipped topics has no usage of url(

Also I found no requirement to have unit test and moreover, this class will be moved to help module #3037230: Finalize the merge of Help Topics into Help

Seems random

Fixing nit, dot at the end of links we trying to prevent to get full url, leaving RTBC

Last patch went without bad topic(

Committed and pushed c42d65e4a7 to 11.x (10.2.x). Thanks!