[faisalahammad]

Description

When local fields are disabled (via acf_disable_local() or the acf/settings/local filter), acf_get_local_store() returns the shared local-empty ACF_Data store. Writes from acf_add_local_field_group() and friends silently accumulate there, and they are still in that shared store the next time the dummy is reached — for example after re-enabling local.

This PR resets the local-empty store inside both acf_enable_local() and acf_disable_local(), so toggle paths discard any registrations that landed while local was disabled.

Changes

includes/local-fields.php

Reset acf_get_store( 'local-empty' ) after each toggle so registrations made while local is disabled cannot carry across toggle boundaries.

function acf_enable_local() {
    acf_enable_filter( 'local' );
    // Clear dummy local-empty store on enable so any registrations that
    // landed there while disabled do not leak back (issue #459).
    acf_get_store( 'local-empty' )->reset();
}

function acf_disable_local() {
    acf_disable_filter( 'local' );
    // Clear dummy local-empty store on disable so registrations made while
    // disabled do not accumulate across toggles (issue #459).
    acf_get_store( 'local-empty' )->reset();
}

Why: The dummy local-empty store is the documented fallback when local is disabled, and it is shared between the fields and groups paths. Discarding its contents on toggle is the smallest fix for the leak.

tests/php/includes/test-local-fields.php

• Updated test_local_setting_filter_disables_local to assert the dummy store is empty after acf_enable_local() runs.
• Added test_disabled_local_clears_dummy_store_on_toggle covering disable → register → enable path.

Reproduction

1. Add an acf/init mu-plugin that sets add_filter( 'acf/settings/local', '__return_false' ) then calls acf_add_local_field_group().
2. Trigger a request — acf_get_store( 'local-empty' )->count() returns 1.
3. Call acf_enable_local().
4. Before this fix: re-enabling surfaces the previously disabled group. After this fix: local-empty count is 0 and the group is not present.

Testing

• composer test — full PHPUnit suite (2846 tests pass).
• composer test:phpstan — targeted run on touched files, no errors.
• composer lint:php — phpcs counts unchanged from baseline.
• New unit tests covering the toggle-clear path.

Closes #459

Use of AI Tools

I used AI tooling to help investigate the bug, draft tests, and verify fix coverage. I reviewed and take responsibility for every change in this PR.

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Props faisalahammad, cbravobernal.

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[cbravobernal]

Thanks for the contribution and the effort here! 🙏

A heads-up on how this repo works: a large part of SCF's codebase (field types, Flexible Content, Blocks v3, local fields, forms, value formatting, and most of includes/ and assets/src/js/) is regularly synced from an upstream codebase. Any change we make there, whether a bug fix or a new feature, gets overwritten or causes hard merge conflicts on the next sync. That includes features behind a beta flag. Fixes for those areas arrive through the sync itself, so we can't accept PRs that touch that code, even good ones.