Disallow unused imports

[sirbrillig]

Add a sniff that prevents use statements that import classes, functions, or constants which are not used.

For example, if I have the line use My\Classname; but Classname is not used anywhere in the file, this would trigger an error.

This adds the rule:

New code MUST NOT import a class, function, or constant without using that import.

[janm6k]

Is this sniff from other coding standard or written from scratch?

I think this one should do the same: https://github.com/slevomat/coding-standard/blob/master/SlevomatCodingStandard/Sniffs/Namespaces/UnusedUsesSniff.php

[sirbrillig]

Is this sniff from other coding standard or written from scratch?

It's written from scratch. I figured one would exist somewhere but I couldn't find it. Clearly you are better at looking than I am. 😁 Theirs looks much more... complete? But mine is much shorter! 😛 Looking through their version I'm trying to come up with a case where mine would fail, but I'm having trouble doing that. I'm inclined to keep my version unless I can come up with a failing test.

[janm6k]

If I understand the difference correctly, this is the case where theirs sniff would detect it, but the shorter one would not detect it:

<?php

use First;
use Second;

new \Third\Second\First();

[Hywan]

We have 4 kind of names in PHP:

1. Unqualified, like C,
2. Qualified, like A\B\C,
3. Relative qualified, like namespace\C,
4. Fully-qualified, like \A\B\C.

I would rename the rule as:

New code MUST NOT use fully-qualified names.

(with a note to remind the kind of names in PHP maybe?)

But the main point of my comment is: It's easier to detect fully-qualified names, than comparing aliases (use) with names. See my comment https://github.com/Automattic/phpcs-neutron-standard/pull/3#discussion_r156016787.

[janm6k]

New code MUST NOT use fully-qualified names.

Situations when I think fully qualified names are better (all fall into category of using a library/wp classes):

• \Stripe\Charge::create express much better that we are using the official library there and not our wrapper
• new \WP_Error - I know for sure when I see it it is the global WP_Error, I don't have to worry about if there is an import on top

[Hywan]

Oh sorry, I guess I misinterprete the whole goal of the rule… I thought it was to forbidden fully-qualified names, but it's not :-p.

[sirbrillig]

If we create a separate repo which is a configuration of different standards (see #13), we could just include the sniff that Jan found there, rather than trying to duplicate it here.

[sirbrillig]

https://github.com/Automattic/phpcs-neutron-ruleset/issues/1 will take care of this.