[D8 only] Add forwards-compatibility shim for assertEqualsCanonicalizing() in phpunit 6&7

Here's a concept. If this works, could also be extended to other FC needs (thinking of assertString(Not)ContainsString, assertIsString, etc)

+++ b/core/tests/Drupal/TestTools/PhpUnitCompatibility/PhpUnit7/TestCompatibilityTrait.php
@@ -39,4 +39,30 @@ public static function assertFalse($actual, string $message = ''): void {
+    $parent = new \ReflectionClass(parent::class);
+    if ($parent->hasMethod('assertEqualsCanonicalizing')) {
+      parent::assertEqualsCanonicalizing($expected, $actual, $message);
+    }
+    else {
+      static::assertEquals($expected, $actual, $message, 0.0, 10, TRUE);
+    }
+  }

Can we just call static::assertEquals() here? Both methods are functionally identical in the final release of PHPUnit 7.5, there will never be a deprecation warning, and so using reflection here seems like over engineering.

Reference: https://github.com/sebastianbergmann/phpunit/blob/7.5.20/src/Framework/A...

#5 I agree, but then we should make clear that we only support PHPUnit 7.5.0 and above in D8, whereas in the composer.json we currently have "phpunit/phpunit": "^6.5 || ^7".

And if we do that, then we do not even need to have ANY method in the PHPUnit7 version of the trait.

Why does this change the version of PHPUnit? parent::assertEquals() will work the same in 7.0.0 up to 7.5.20 unless I am missing something?

edit: in both cases I wrote parent::assertEquals() but really I should say static::assertEquals()!

@longwave you're right, thanks

from https://www.php.net/manual/en/language.oop5.traits.php :

Precedence

An inherited member from a base class is overridden by a member inserted by a Trait. The precedence order is that members from the current class override Trait methods, which in turn override inherited methods.

Here we go.

Looks great, as simple as it can be.

OK I'll do the re-roll

Re-rolled patch #9 for core 8.8

removing re-roll tag

Reroll looks good.

We should put a brief note in the 8.9.0 release notes that a forward-compatibility layer for PHPUnit 9 is provided, and mention it in the 8.8.6 release notes since technically backporting this API is outside our allowed changes policy and there's a small risk it might be disruptive with method name collisions.

Oops, this issue is missing a CR. We could add the issue to the CR for #3126787: [D8 only] Add forwards-compatibility shim for assertInternalType() replacements in phpunit 6&7 and cover all the BC layer methods in one place.

Added a CR.
The CR is not jet published, therefor putting the status to RTBC.

Thanks @daffie -- I guess a separate CR is OK too. Published the CR.