Get repeater data via providesContext/usesContext

[JiveDig]

Originally brought up via #654 (comment)

It seems we only have access to the raw data, which is understandable, but it would be great to get the return value as expected via get_field().

@lgladdy originally posted:

In the future, I'd expect we'll get some kind of acf_build_context_data() function into core for you, but given this context was just a quick thing I managed to get into the 6.0 release as an MVP, we'll work more on this over our next few releases.

This is a new issue to keep the discussion focused on this specific FR.

[JiveDig]

FWIW, this works but is messy:

// $context is the acf/fields data.

// Key => Default.
$repeaters    = [
	'arrangement'    => '1/4',
	'arrangement_md' => '1/3',
	'arrangement_sm' => '1/2',
	'arrangement_xs' => '1/1',
];

$args = [];

foreach ( $repeaters as $name => $default ) {
	$args[ $name ] = [];

	$value = isset( $context[ $name ] ) ? $context[ $name ] : null;

	if ( is_null( $value ) ) {
		$args[ $name ][] = $default;
		continue;
	}

	// Array starts with 0 but rows count starts with 1.
	for ( $i = 0; $i < (int) $value; $i++ ) {
		$sub_key         = sprintf( '%s_%s_columns', $name, $i );
		$sub_value       = isset( $context[ $sub_key ] ) ? $context[ $sub_key ] : [ $default ];
		$args[ $name ][] = $sub_value;
	}
}

While this is cleaner but only gets the first row, or at least I think that's what's happening:

// $context is the acf/fields data.
$setup = acf_setup_meta( $context, 'block_context' );

// Key => Default.
$repeaters    = [
	'arrangement'    => '1/4',
	'arrangement_md' => '1/3',
	'arrangement_sm' => '1/2',
	'arrangement_xs' => '1/1',
];

$args = [];

foreach ( $repeaters as $name => $default ) {
	$args[ $name ] = [];
	$values        = get_field( $name, 'block_context' );

	if ( ! $values ) {
		$args[ $name ][] = $default;
		continue;
	}

	foreach ( (array) $values as $value ) {
		$args[ $name ][] = isset( $value['columns'] ) ? $value['columns'] : $default;
	}
}