is_preview was called incorrectly notice on every early get_field() since 6.8.10 (acf_revisions::acf_validate_post_id)

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Since Oct 12, 2026.

  • #1049 by @faisalahammad — open

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
78/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
php
Domain
backend

Research direction

Start in includes/revisions.php at acf_revisions::acf_validate_post_id() and review its acf/validate_post_id hook and early preview check. Reproduce the plugins_loaded get_field() call with WP_DEBUG enabled, then verify that early reads no longer log the is_preview notice while normal preview validation remains intact.

Written by the indexing model from the issue text.

Description

is_preview was called incorrectly notice on every early get_field() since 6.8.10

Environment
  • ACF PRO 6.8.10
  • WordPress 7.0 (multisite)
  • PHP 8.4
  • WP_DEBUG enabled
Description

Since 6.8.10, any get_field() / get_option()-style ACF read made before WordPress creates the main query triggers a PHP notice:

PHP Notice: Function is_preview was called incorrectly. Conditional query tags do not work before the query is run. Before then, they always return false. (This message was added
in version 3.1.0.) in wp-includes/functions.php on line 6131

The notice fires on every such call, so production logs fill up quickly. It also breaks sites that convert notices to exceptions: with Whoops in development, the request ends in
a 500.

Cause

acf_revisions::acf_validate_post_id() (includes/revisions.php) is hooked to acf/validate_post_id, so it runs on every field read. In 6.8.10 its early bail changed:

- // bail early if no preview in URL
- if ( ! isset( $_GET['preview'] ) ) {
+ // Bail early if not a well-formed WordPress preview context.
+ if ( ! is_preview() ) {
      return $post_id;
  }

is_preview() calls _doing_it_wrong() when the global $wp_query is not set yet. WordPress only creates it in wp-settings.php after plugins_loaded. Reading options while
plugins load (settings, feature flags, service bootstrapping) is a common and legitimate pattern, and before 6.8.10 it produced no notice.

Steps to reproduce

  1. Enable WP_DEBUG and WP_DEBUG_LOG.

  2. Add to any plugin:

    add_action( 'plugins_loaded', function () {
    get_field( 'any_field', 'option' );
} );

  3. Load any front-end page.

Expected

No notice, as in 6.8.9 and earlier.

Actual

The is_preview was called incorrectly notice is logged on every call.

Suggested fix

Before the main query exists, is_preview() returns false anyway, so bailing out without calling it keeps the behavior identical:

global $wp_query;

if ( ! isset( $wp_query ) || ! is_preview() ) {
    return $post_id;
}
Workaround

Right after ACF loads, we replace ACF's callback on acf/validate_post_id with a wrapper. The wrapper calls acf()->revisions->acf_validate_post_id() only when
$GLOBALS['wp_query'] is set.

Dominant language
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