[8.x] Change Arr::toCssClasses to Arr::conditionallyToString to be more abstract

[NickSdot]

The functionality introduced with #38016 is very useful. Thanks @danharrin! I might be a little late with this because it already got merged, and it's also maybe a little pedantic, but I still would like to try to make a point.

From my point of view the introduced array helper is too specific to a special situation. I see several use cased for the same functionality. If the framework starts to add helpers for each specific case, I could get bloated quite fast.

What does the array helper function actually do? It conditionally creates a string from a given array.

Hence, I would like to propose to change Arr::toCssClasses to Arr::conditionallyToString and add a little extra flexibility with the newly added parameter $separator.

Changes

Before:

public static function toCssClasses($array)
    {
        $classList = static::wrap($array);

        $classes = [];

        foreach ($classList as $class => $constraint) {
            if (is_numeric($class)) {
                $classes[] = $constraint;
            } elseif ($constraint) {
                $classes[] = $class;
            }
        }

        return implode(' ', $classes);
    }

After:

public static function conditionallyToString($array, $separator = ' ')
    {
        $array = static::wrap($array);

        $values = [];

        foreach ($array as $key => $value) {
            if (is_numeric($key)) {
                $values[] = $value;
            } elseif ($value) {
                $values[] = $key;
            }
        }

        return implode($separator, $values);
    }

Benefit

Function is re-usable to conditionally create any kind of string from an array.

Let's say I want to create a - separated string from an array. I can use:

$classes = Arr::conditionallyToString([
            'we',
            'do',
            'not' => false,
            'want',
            'to' => true,
            'build',
            'something' => true,
            'slug',
            'like'
        ], '-');

        // result: 'we-do-want-to-build-something-slug-like

Or I want to have a , separated list of people attending to an event:

        $values = Arr::conditionallyToString([
            'Taylor',
            'John',
            'Sponge Bob' => false,
            'Dave' => true,
        ], ', ');

        // result: Taylor, John, Dave'

Breaking change or not?

Technically this is a breaking change, because the new function just got merged and released. One could argue that no one is using the new function now.

In worst case there could be a non documented alias from Arr::toCssClasses to the more abstract Arr::conditionallyToString. This would not bloat the framework less in the specific case, but would enable developers to use a properly named function for teir own purpose.

Notes

1. Blade stuff is changed to the new function name
2. Tests are changed to the new function name and a cases for the new $separator parameter got added.
3. This pull request requires changes in the newly added documentation items (@class Blade directive and array helper docs#7194)
4. For better comparability I did not yet move the function to be in alphabetical order in Arr::class. Happy to do that in case the PR is considered to be merged

[taylorotwell]

No plans to change this for now.