field_help() no longer lists field_type/widget modules and can throw undefined index notice.

Looks good to me, thanks Julien :)

Could we get the steps to reproduce in the original post into a simple automated test for Help module? It's really odd that we don't have test coverage for this bunch of code.

Wrote the tests for this, it turns out that the field help page is currently broken, since it still relies on hook_field_info(), which no longer exists ([#2064123]).

Changed field_help() to make use of the FieldTypePluginManager and WidgetPluginManager to fetch the list of modules to render, and added a couple of test cases (including a test for the notice reported in this issue).

Re-titling and classifying as bug to better reflect new situation.

Removing the "Needs tests" tag.

Great! Can you please upload a test-only patch that will fail, thus confirming that the fixes are valid?

Sure, test-only patch, followed by complete patch from #5

Hmmm. The failing test seems totally unrelated to this change, and it succeeds on my local machine, so requesting a retest.

#8: 2099261-5-field-help-page.patch queued for re-testing.

The actual help text for field_help() is outdated, but this is tackled in #2091319: Update hook_help for Field module.

Ok, patches fail/pass as expected, back to RTBC.

Patch no longer applies.

That's because of a couple of use statements at the top of field.module that weren't actually needed, here's a reroll.

Committed and pushed to 8.x. Thanks!

+++ b/core/modules/field/lib/Drupal/field/Tests/FieldHelpTest.php
@@ -0,0 +1,69 @@
+    $this->assertNoLink('Telephone', 'Modules with field types that do not implement hook_help are not linked.');

This broke #2078813: Create hook_help for telephone module, and since all modules should have hook_help(), this is not really a great assumption. Can we remove the assertion, or should we write a new test field type module that doesn't have hook_help()? Please answer on the other issue.

I'll rewrite the assertion so they use a test module instead of a core module.

...and here is a more sane way to test, using the existing field_test module to verify that modules implementing a widget and not having a hook_help() implementation list but not link to that module.

Might need a re-roll after #2078813: Create hook_help for telephone module lands.

nm, after discussing with tim.plunkett and webchick in IRC, we decided this can be combined in #2078813: Create hook_help for telephone module