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Fix: preserve parent presets when saving child theme changes #893

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Fix: preserve parent presets when saving child theme changes #893

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123 changes: 123 additions & 0 deletions includes/create-theme/resolver_additions.php
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,16 @@ public static function export_theme_data( $content, $extra_theme_data = null ) {

$data = $theme->get_data();

if ( 'current' === $content && $current_theme->parent() ) {
$parent_file = static::get_file_path_from_theme( 'theme.json', true );
if ( $parent_file ) {
$parent_data = static::read_json_file( $parent_file );
if ( is_array( $parent_data ) ) {
$data = static::merge_parent_preset_arrays( $data, $parent_data );
}
}
}

// Add the schema.
if ( empty( $schema ) ) {
global $wp_version;
Expand All @@ -102,6 +112,119 @@ public static function export_theme_data( $content, $extra_theme_data = null ) {
return static::stringify( $data );
}

/**
* Merge parent theme preset arrays into child theme data.
*
* For child themes, WordPress Core replaces indexed preset arrays (like color palettes,
* font sizes, gradients) entirely rather than merging them. This method traverses
* child data and backfills parent preset entries for any preset array present in child data,
* with child entries overriding parent entries that share the same slug.
*
* @param array $child_data Child theme data.
* @param array $parent_data Parent theme data.
* @return array Merged theme data.
*/
public static function merge_parent_preset_arrays( array $child_data, array $parent_data ) {
if ( empty( $child_data ) || empty( $parent_data ) ) {
return $child_data;
}

$result = $child_data;

foreach ( $child_data as $key => $child_value ) {
// Non-arrays (scalars, booleans, null) are already preserved in $result.
if ( ! is_array( $child_value ) ) {
continue;
}

// Associative objects (settings, color, blocks, etc.): recurse.
if ( ! static::is_list( $child_value ) ) {
$parent_subdata = ( isset( $parent_data[ $key ] ) && is_array( $parent_data[ $key ] ) ) ? $parent_data[ $key ] : array();
$result[ $key ] = static::merge_parent_preset_arrays( $child_value, $parent_subdata );
continue;
}

// Slug-keyed preset lists: backfill parent entries if parent defines this preset.
if ( static::is_preset_list( $child_value ) && isset( $parent_data[ $key ] ) && static::is_preset_list( $parent_data[ $key ] ) ) {
$result[ $key ] = static::merge_preset_list( $child_value, $parent_data[ $key ] );
}
}

return $result;
}

/**
* Check whether a value is a slug-keyed preset list (e.g. palette, fontSizes).
*
* @param mixed $value Value to check.
* @return bool Whether the value is a preset list.
*/
private static function is_preset_list( $value ) {
return is_array( $value )
&& static::is_list( $value )
&& ! empty( $value )
&& is_array( $value[0] )
&& isset( $value[0]['slug'] );
}

/**
* Merge parent and child preset lists keyed by slug.
*
* Preserves parent item order with child overrides replacing parent items
* at their original positions, and new child entries appended.
*
* @param array $child_list Child preset list.
* @param array $parent_list Parent preset list.
* @return array Merged preset list.
*/
private static function merge_preset_list( array $child_list, array $parent_list ) {
$merged = array();
$slug_to_index = array();

foreach ( $parent_list as $item ) {
if ( is_array( $item ) && isset( $item['slug'] ) ) {
$slug_to_index[ $item['slug'] ] = count( $merged );
}
$merged[] = $item;
}

foreach ( $child_list as $item ) {
if ( is_array( $item ) && isset( $item['slug'] ) && isset( $slug_to_index[ $item['slug'] ] ) ) {
$merged[ $slug_to_index[ $item['slug'] ] ] = $item;
} else {
if ( is_array( $item ) && isset( $item['slug'] ) ) {
$slug_to_index[ $item['slug'] ] = count( $merged );
}
$merged[] = $item;
}
}

return $merged;
}

/**
* Detect whether an array is a list (sequential integer keys starting at 0).
* Mirrors PHP 8.1+ `array_is_list()`.
*
* @param array $arr Array to check.
* @return bool Whether the array is a list.
*/
private static function is_list( array $arr ) {
if ( function_exists( 'array_is_list' ) ) {
return array_is_list( $arr );
}
if ( array() === $arr ) {
return true;
}
$expected = 0;
foreach ( $arr as $key => $_v ) {
if ( $key !== $expected++ ) {
return false;
}
}
return true;
}

/**
* Get the user data.
*
Expand Down
120 changes: 120 additions & 0 deletions tests/test-resolver-preset-merge.php
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Original file line number Diff line number Diff line change
@@ -0,0 +1,120 @@
<?php
/**
* @package Create_Block_Theme
*/
class Test_Resolver_Preset_Merge extends WP_UnitTestCase {

public function set_up() {
parent::set_up();
if ( ! class_exists( 'CBT_Theme_JSON_Resolver' ) && function_exists( 'cbt_augment_resolver_with_utilities' ) ) {
cbt_augment_resolver_with_utilities();
}
}

public function test_merge_appends_child_presets_and_overrides() {
$parent = array(
'settings' => array(
'color' => array(
'palette' => array(
array(
'slug' => 'base',
'color' => '#ffffff',
'name' => 'Base',
),
array(
'slug' => 'contrast',
'color' => '#000000',
'name' => 'Contrast',
),
),
),
),
);

$child = array(
'settings' => array(
'color' => array(
'palette' => array(
array(
'slug' => 'base',
'color' => '#f0f0f0',
'name' => 'Custom Base',
),
array(
'slug' => 'accent',
'color' => '#0073aa',
'name' => 'Accent',
),
),
),
),
);

$result = CBT_Theme_JSON_Resolver::merge_parent_preset_arrays( $child, $parent );
$palette = $result['settings']['color']['palette'];

$this->assertCount( 3, $palette );
$this->assertSame( array( 'base', 'contrast', 'accent' ), array_column( $palette, 'slug' ) );
$this->assertSame( '#f0f0f0', $palette[0]['color'] );
$this->assertSame( 'Custom Base', $palette[0]['name'] );
$this->assertSame( '#000000', $palette[1]['color'] );
$this->assertSame( '#0073aa', $palette[2]['color'] );
}

public function test_merge_empty_child_preset_clears() {
$parent = array(
'settings' => array(
'color' => array(
'palette' => array(
array(
'slug' => 'base',
'color' => '#ffffff',
'name' => 'Base',
),
),
),
),
);

$child = array(
'settings' => array(
'color' => array(
'palette' => array(),
),
),
);

$result = CBT_Theme_JSON_Resolver::merge_parent_preset_arrays( $child, $parent );
$this->assertSame( array(), $result['settings']['color']['palette'] );
}

public function test_merge_preserves_non_preset_deltas() {
$parent = array(
'settings' => array(
'layout' => array(
'contentSize' => '645px',
'wideSize' => '1200px',
),
'spacing' => array(
'units' => array( '%', 'px', 'em' ),
),
),
);

$child = array(
'settings' => array(
'layout' => array(
'contentSize' => '800px',
),
'spacing' => array(
'units' => array( '%', 'rem' ),
),
),
);

$result = CBT_Theme_JSON_Resolver::merge_parent_preset_arrays( $child, $parent );

$this->assertSame( array( 'contentSize' => '800px' ), $result['settings']['layout'] );
$this->assertSame( array( '%', 'rem' ), $result['settings']['spacing']['units'] );
}
}
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