Mirror Store API product taxonomy operators in WCPOS REST

[kilbot]

Follow-up from wcpos/monorepo#513 and #1072.

Context

The app-side query translator now mirrors Woo Store API taxonomy filter names for product filters:

• category + category_operator
• tag + tag_operator
• brand + brand_operator

The companion WooCommerce POS API PR currently adds server-side support for brand and brand_operator, but does not yet add custom REST support for category_operator or tag_operator. If WooCommerce REST products ignores those params, client-side $and taxonomy semantics may not be honored server-side.

Goal

Mirror Woo Store API product taxonomy filter behavior in the WCPOS REST products endpoint until WooCommerce REST adds native support.

Relevant Store API params documented by WooCommerce:

• category_operator: in, not_in, and
• tag_operator: in, not_in, and
• brand_operator: in, not_in, and
• _unstable_tax_[product-taxonomy]
• _unstable_tax_[product-taxonomy]_operator

Docs: https://developer.woocommerce.com/docs/apis/store-api/resources-endpoints/products/

Requirements

• Add WCPOS REST support for category_operator and tag_operator if WC REST does not already support them.
• Keep the same future-proofing pattern used for brand: if parent WooCommerce REST adds native support later, defer to the parent and avoid duplicate tax queries.
• Confirm whether WooCommerce REST already supports any of these operator params in the installed Woo version.
• Add PHPUnit coverage for category_operator=and|not_in and tag_operator=and|not_in.
• Consider whether _unstable_tax_[product-taxonomy] parity is needed for custom product taxonomies.

Related PRs

• Client translation: Fix product query filters and auth fallback monorepo#513
• Initial brand support: Add Store API taxonomy REST filters #1072

[kilbot]

Shipped in PR #1072 (merged 2026-05-25): taxonomy operators in product filters incl. tests. (Closed during the 2026-06-11 roadmap review — evidence-verified and approved by @kilbot. Reopen if this is wrong.)