Page dropdown walker must check selected against value field

[geminorum]

Walker_PageDropdown only checks selected with the page ID and ignores value_field option.

[SergeyBiryukov]

Related: #43522

Refreshing 41471.diff for Testing and Review Purposes

Trac ticket: https://core.trac.wordpress.org/ticket/41471

[SirLouen]

Reproduction and Patch Testing Report

Description

✅ This report validates that the indicated issue can be reproduced and patch works as expected.

Patch tested: ​https://github.com/WordPress/wordpress-develop/pull/10203

Environment

• WordPress: 6.9-alpha-60093-src
• PHP: 8.2.29
• Server: nginx/1.29.1
• Database: mysqli (Server: 8.4.6 / Client: mysqlnd 8.2.29)
• Browser: Chrome 140.0.0.0
• OS: Windows 10/11
• Theme: Twenty Seventeen 3.9
• MU Plugins: None activated
• Plugins:
  • BBB Testing Dolly
  • Classic Editor 1.6.7
  • Test Reports 1.2.0

Testing Instructions

1. Create a new page with the slug test-slug-page
2. Create two or three other pages for the example
3. Add the shortcode to a plugin or wherever it can be executed
4. Add the shortcode to anotherpage
5. The page with the test-slug-page slug should be selected by default

Actual Results

1. ✅ Issue resolved with patch.

Additional Notes

• Given that we are already setting by default the ID to $argsvalue_field, having the option of assigning whatever value_field we prefer, as provided in the example in supp artifacts, improves this.
• This must be upgraded to enhancement as this is not a bug per se.
• Some unit test coverage for this would be ideal.

Supplemental Artifacts

function test_page_dropdown() {
    get_pages();
    $dropdown = wp_dropdown_pages( array(
        'echo' => 0,
        'value_field' => 'post_name',
        'selected' => 'test-slug-page',
        'name' => 'test_dropdown',
        'show_option_none' => 'Select a page',
    ) );
    echo $dropdown;
}
add_shortcode( 'test_dropdown', 'test_page_dropdown' );