Custom query on relationship is not called when Query returns Union type

[edgarsn]

Summary

When GraphQL query returns Union Type, it doesn't call custom query on relationship field.

Issue here - #900

As I discussed with @mfn I'm a bit confused how to solve this bug. From my initial observations, it looks like it may involve major code rewrites to fix it, but I could be wrong. I don't have that much knowledge how this package works under the hood, the least I can help with is add tests showing the bug.

I'll appreciate anyone who might want to look at this.

Context

PostType.php

This should only query comments where title column value is lorem.

'comments' => [
	'type' => Type::nonNull(Type::listOf(Type::nonNull(GraphQL::type('Comment')))),
	'query' => function (array $args, $query, $ctx) {
		$query->where('title', 'like', 'lorem');
	},
],

SearchUnionTest.php

• On line 35, we create a comment for a post with title lorem.
• On line 36, we create a comment for a post with title ipsum. This should not be included in results.

But it returns both comments.

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Type of change:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Misc. change (internal, infrastructure, maintenance, etc.)

Checklist:

• Existing tests have been adapted and/or new tests have been added
• Add a CHANGELOG.md entry
• Update the README.md
• Code style has been fixed via composer fix-style

[mfn]

Nice, thanks, that's all we need for now!

I've fixed the remaining code style issue in #971 and also added the (wrong) 2nd comment to the assertion and documented what the problem with it is.

Even though there's no ETA for working on a fix, at least now we've a test documenting the current wrong behaviour and if it gets eventually fixed, we already have a test which is expected to flip!