[Sabbir345]

Trac ticket: https://core.trac.wordpress.org/ticket/41604

A request to /wp/v2/settings that contains a setting that is not registered (or not exposed with show_in_rest) returns a 200 response, and the setting is silently ignored:

POST /wp/v2/settings  {"this_setting_does_not_exist": "value"}  → 200 (expected 400)

This PR returns a 400 rest_invalid_param error when the request body contains a setting that is not registered. The query string is not checked.

Why only the request body

The two previous fixes (r60301, r60357) were reverted in r61324 because they rejected valid requests that use the query string. The two open PRs, #10662 and #12967, use an allow-list of global parameters instead, but any parameter missing from that list breaks requests again. For example, on a site with plain permalinks every REST request is sent as /?rest_route=/wp/v2/settings, and WP_REST_Server::serve_request() passes $_GET as-is, so rest_route becomes a request parameter. With either open PR applied, saving any setting on such a site returns 400 Invalid parameter(s): rest_route.

The query string can contain:

• settings, which are supported there in place of the body (the Web Stories case in comment:33),
• global parameters such as rest_route and _locale (comment:7),
• parameters added by other code, such as cache busters.

None of these can be reliably told apart from a mistyped setting, so the query string is left as it is. The request body has no such ambiguity, apart from global parameters, which are prefixed with an underscore and are ignored.

Changes

• WP_REST_Settings_Controller::update_item() returns 400 rest_invalid_param ("Invalid parameter(s): …") if the form or JSON body contains a setting that is not registered. No settings are updated in that case.
• Body parameters prefixed with an underscore (_wpnonce, _method, _locale, …) are ignored.
• The error message reuses the existing Invalid parameter(s): %s string, so there is no new string to translate.

Notes

• An empty request is not rejected. Rejecting it is what broke requests that pass settings only in the query string, and the ticket is about unknown settings.
• An unknown setting passed only in the query string is still ignored, as before.
• Follow-up to r60301, r60357, and r61324.

Testing

New tests in tests/phpunit/tests/rest-api/rest-settings-controller.php:

• An unregistered setting in a form body (POST) and a JSON body (POST and PUT) returns a 400, and neither setting is updated. These fail on trunk.
• The request still succeeds with ?rest_route=/wp/v2/settings, ?_locale=user, an unknown query parameter, a setting in the query string with an empty body, and _wpnonce in the body.

npm run test:php -- --filter WP_Test_REST_Settings_Controller
npm run test:php -- --group restapi

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