[policy, no patch] Use declare(strict_types=1) in new code

+1

Re #2. I guess many tests will be broken because of passing null values to string functions.

Sometimes you just want to create a fun patch hehe.

+1 — existing code won't be affected if we start doing this for new files only for now.

rebased, moving files confused it.

Whitespace.

+1

+1 here also.

Bit unfrotunate cspell fails, locallty it doesnt :/

Remaining tasks
Decide whether this is a good idea.
Decide on a standard for adding declare(strict_types=1); to files

So far no one objected, so the first part of the issue can be considered as completed. Right?

As of coding standard it actually consists of two independent rules.
1. Whether or not put spaces around =.
2. Where to place the declaration. On the same line as opening php tag or on a new line below.

I like the way it is placed in PhpUnit.
https://github.com/sebastianbergmann/phpunit/blob/9.5/src/Exception.php#L1
Though I would prefer it having spaces around =.
Example:
<?php declare(strict_types = 1);

That issue is an interesting read. Would recommend.

There is an argument that if we use PHPStan we should not need PHP's strict typing, as PHPStan can do all this and more.

Not exactly.
PHPStan is a static code analyzer.
declare(strict_types = 1) works on runtime.

In most of the cases PHPStan can give a warning, but not all the time.

I know that, a lot of library (PHPUnit was mentioned before) puts the declare statement in the same line.
<?php declare(...);

I am not fun of that style.
strict_types is not the only thing that can be declared.
https://www.php.net/manual/en/control-structures.declare.php

Right now there is only three of them, maybe more to come in the future.
ticks and encoding won't be used in core and contrib any time soon,
but I would like to use a one statement per line style.

<?php

declare(strict_types = 1);
declare(encoding = 'ISO-8859-1');
?>

Re #17. In reality, strict_types is the only declare statement in use.

This declares can go away in PHP 9.0 https://externals.io/message/112230#112233

Came across this and I decided to create an MR to see the failures.

Good idea @quetone, I had thought about doing the same. I think fixing most of #3404246: [META] Fix strict type errors detected by phpstan would go a long way to getting this green. From memory there were no reported errors in core/lib/Drupal/Component, so maybe we could try limit to just that area first.

Seems I didn't do Components in the MR, so I have added that now.

There is consensus here that this is a good idea and the standard for adding the declaration has also been agreed to. So, the policy has been agreed to.

Does this require documentation? If so, where?

FYI, the latest MR added strict types to Components and that is failing. The MR is information only and is not needed to resolve this policy issue.

The Needs Review Queue Bot tested this issue. It no longer applies to Drupal core. Therefore, this issue status is now "Needs work".

This does not mean that the patch necessarily needs to be re-rolled or the MR rebased. Read the Issue Summary, the issue tags and the latest discussion here to determine what needs to be done.

Consult the Drupal Contributor Guide to find step-by-step guides for working with issues.

As stated in #26, the MR is for information only.

There is one remaining question, where to document?

I don't know of any docs specific to "how to write good code for Core" anywhere. 😅 Here are some of the spots I found while searching for a home:

https://www.drupal.org/community/contributor-guide/skill/php-codingprogr...
https://www.drupal.org/community/contributor-guide/task/create-a-merge-r...

Neither of those are particularly discoverable or exactly relevant.

Probably more likely to be found if we considered this a "Coding standard" not a core-only policy, but that's a bit of a slippery slope.

Maybe we want a new child page under https://www.drupal.org/about/core/policies for stuff like this. Something like "Core coding policies". Would also be somewhere to document the outcome of #3488476: [policy, no patch] Allow using @final when a class is not considered as an extension point vs. #3019332: Use final to define classes that are NOT extension points. We could write up #3154762: [policy, no patch] All new Drupal 10 code should use appropriate type hints wherever possible there, too.

While we're discussing if we want to do this, I figured we could do this fairly simply with a git diff in a gitlab ci job. Opened #3529705: Enforce strict types in new code with a proof of concept.

I think the easiest thing is to just place it in the coding standards.

We already do this in practice, we should document this and make it a standard.

Created a follow up in Coding standards to discuss making this a requirement for all new code. #3630579: Use declare(strict_types=1) in new code

catch brought this up in committer channels where I and @mstrelan participated in the discussion. There is agreement to do this, and it is already being done in core. There is now a follow up in Coding Standards to discuss implementing in the standards, and there #3529705: Enforce strict types in new code to implement this for core.

Therefor, closing this policy issue as fixed.

Thanks everyone for helping to resolve this.