fix(domain): skip auto domain-record creation when site uses a checkout-form base domain

[superdav42]

Summary

In subdirectory multisite, an operator can publish an alternate base
domain via the checkout form's Site URL field (available_domains /
available_domains_multi). When customers register subsites under that
alternate base — for example example.com/<slug> on a network whose
primary host is wp.example.test — the previous check in
Domain_Manager::handle_site_created():

$has_subdomain = str_replace($current_site->domain, '', $site->domain);

treated the alternate base as a per-subsite custom mapping and produced a
primary_domain = true Domain record for the shared base against every
newly registered subsite. That row then caused Mercator/sunrise to route
all <base>/* traffic to the single subsite owning the mapping and
404 every sibling subsite — until the operator manually deleted the row
from Ultimate Multisite → Domains.

Reproduction (matches the customer report)

1. Subdirectory multisite installed on wp.example.test.
2. In the checkout form's Site URL field, set Enable Domain Selection
   = on and Available Domains = example.com.
3. Customer registers, selecting example.com → site example.com/tenant.
4. Open Ultimate Multisite → Domains: a row for example.com (mapped
   to the new subsite, primary_domain = true, stage = checking-dns)
   has been created automatically.
5. Visit any other subsite under example.com/... → Page not found.
6. Delete the row → all subsites resolve again.

Fix

Introduce Domain_Manager::is_network_base_domain($domain), which
recognises both the network primary and any operator-configured
checkout-form base domain. Use it in handle_site_created() and
handle_site_deleted() instead of the simple string test.

Two extension seams are added for addons/integrations:

• wu_should_create_domain_record_for_site (bool, \WP_Site) —
  return false to suppress the automatic Domain record from anywhere.
• wu_checkout_form_base_domains (string[]) — declare extra
  network-base hosts (e.g. hosts provisioned by a host-provider
  integration) so they are also excluded from auto-mapping.

The DB scan that walks every published checkout form's site_url field
is memoised per request, but the wu_checkout_form_base_domains filter
is re-applied on every call so addons (and tests) can override the list
without restarting the request.

Files changed

• inc/managers/class-domain-manager.php — new helpers
  is_network_base_domain(), get_checkout_form_base_domains(),
  collect_checkout_form_base_domains(), normalize_base_domain();
  handle_site_created() and handle_site_deleted() now use them and
  expose the new filters.
• tests/WP_Ultimo/Managers/Domain_Manager_Test.php — 8 new regression
  tests (see below).

Behaviour delta

Scenario	Before	After
Subsite at tenant.network.test (real subdomain) on a network rooted at network.test	Domain record auto-created	unchanged — still auto-created
Subsite at network.test/tenant (network primary)	Skipped	unchanged — still skipped
Subsite at example.com/tenant on a network rooted at wp.example.test with example.com listed in checkout form available_domains	Domain record auto-created → breaks siblings	Skipped — siblings keep working
Subsite at customer-brand.com (real per-site mapping, not in any checkout form)	Domain record auto-created	unchanged — still auto-created

The change is strictly additive: hosts not listed in any checkout form
and not equal to the network primary still produce a mapped-domain
record exactly as before.

Verification

cd /home/dave/Git/ultimate-multisite--checkout-available-domains-auto-mapping
vendor/bin/phpcs inc/managers/class-domain-manager.php tests/WP_Ultimo/Managers/Domain_Manager_Test.php   # ✅ 0 errors on new code
vendor/bin/phpstan analyse                                                                                # ✅ pre-commit hook: 0 errors
vendor/bin/phpunit --filter 'Domain_Manager_Test' --no-coverage                                           # ✅ 145 tests, 337 assertions

The 8 new tests:

• test_is_network_base_domain_matches_network_primary
• test_is_network_base_domain_normalises_host (case, www.)
• test_is_network_base_domain_rejects_unknown_host
• test_is_network_base_domain_honours_filter
• test_handle_site_created_skips_domain_record_for_checkout_form_base (regression)
• test_handle_site_created_respects_should_create_filter
• test_handle_site_deleted_skips_remove_for_checkout_form_base (regression)
• test_normalize_base_domain_handles_varied_inputs

Two failures observed in Signup_Field_Site_Url_Test::test_to_fields_array_with_domain_selection
and Site_Manager_Test::test_site_network_id reproduce identically on
main (commit 1511f868) and are unrelated to this PR.

Related history

• 793057d2 — fix(checkout): use available_domains for auto-generated site URLs (fix(checkout): use available_domains for auto-generated site URLs #1072)
• 41ea2f23 — fix: site provisioning hardening — limitations, membership inference, domain promotion (fix: site provisioning hardening — limitations, membership inference, domain promotion #965)
• 702e0c58 — fix: auto-promote custom domain to primary on DNS verification (fix: auto-promote custom domain to primary on DNS verification for 3-part domains #991)

#1072 made available_domains actually flow into the new site's
domain column (good); this PR closes the matching gap on the
Domain_Manager side so the alternate base is recognised as a shared
network base, not a per-site mapping.

---

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• inc/managers/class-domain-manager.php
• tests/WP_Ultimo/Managers/Domain_Manager_Test.php

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• Commit unit tests in branch fix/checkout-available-domains-auto-mapping

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[superdav42]

Summary

In subdirectory multisite, an operator can publish an alternate base
domain via the checkout form's Site URL field (available_domains /
available_domains_multi). When customers register subsites under that
alternate base — for example example.com/<slug> on a network whose
primary host is wp.example.test — the previous check in
Domain_Manager::handle_site_created():

$has_subdomain = str_replace($current_site->domain, '', $site->domain);

treated the alternate base as a per-subsite custom mapping and produced a
primary_domain = true Domain record for the shared base against every
newly registered subsite. That row then caused Mercator/sunrise to route
all <base>/* traffic to the single subsite owning the mapping and
404 every sibling subsite — until the operator manually deleted the row
from Ultimate Multisite → Domains.

Reproduction (matches the customer report)

1. Subdirectory multisite installed on wp.example.test.
2. In the checkout form's Site URL field, set Enable Domain Selection
   = on and Available Domains = example.com.
3. Customer registers, selecting example.com → site example.com/tenant.
4. Open Ultimate Multisite → Domains: a row for example.com (mapped
   to the new subsite, primary_domain = true, stage = checking-dns)
   has been created automatically.
5. Visit any other subsite under example.com/... → Page not found.
6. Delete the row → all subsites resolve again.

Fix

Introduce Domain_Manager::is_network_base_domain($domain), which
recognises both the network primary and any operator-configured
checkout-form base domain. Use it in handle_site_created() and
handle_site_deleted() instead of the simple string test.
Two extension seams are added for addons/integrations:

• wu_should_create_domain_record_for_site (bool, \WP_Site) —
  return false to suppress the automatic Domain record from anywhere.
• wu_checkout_form_base_domains (string[]) — declare extra
  network-base hosts (e.g. hosts provisioned by a host-provider
  integration) so they are also excluded from auto-mapping.
  The DB scan that walks every published checkout form's site_url field
  is memoised per request, but the wu_checkout_form_base_domains filter
  is re-applied on every call so addons (and tests) can override the list
  without restarting the request.

Files changed

• inc/managers/class-domain-manager.php — new helpers
  is_network_base_domain(), get_checkout_form_base_domains(),
  collect_checkout_form_base_domains(), normalize_base_domain();
  handle_site_created() and handle_site_deleted() now use them and
  expose the new filters.
• tests/WP_Ultimo/Managers/Domain_Manager_Test.php — 8 new regression
  tests (see below).

Behaviour delta

Scenario	Before	After
Subsite at tenant.network.test (real subdomain) on a network rooted at network.test	Domain record auto-created	unchanged — still auto-created
Subsite at network.test/tenant (network primary)	Skipped	unchanged — still skipped
Subsite at example.com/tenant on a network rooted at wp.example.test with example.com listed in checkout form available_domains	Domain record auto-created → breaks siblings	Skipped — siblings keep working
Subsite at customer-brand.com (real per-site mapping, not in any checkout form)	Domain record auto-created	unchanged — still auto-created
The change is strictly additive: hosts not listed in any checkout form
and not equal to the network primary still produce a mapped-domain
record exactly as before.

Verification

cd /home/dave/Git/ultimate-multisite--checkout-available-domains-auto-mapping
vendor/bin/phpcs inc/managers/class-domain-manager.php tests/WP_Ultimo/Managers/Domain_Manager_Test.php   # ✅ 0 errors on new code
vendor/bin/phpstan analyse                                                                                # ✅ pre-commit hook: 0 errors
vendor/bin/phpunit --filter 'Domain_Manager_Test' --no-coverage                                           # ✅ 145 tests, 337 assertions

The 8 new tests:

• test_is_network_base_domain_matches_network_primary
• test_is_network_base_domain_normalises_host (case, www.)
• test_is_network_base_domain_rejects_unknown_host
• test_is_network_base_domain_honours_filter
• test_handle_site_created_skips_domain_record_for_checkout_form_base (regression)
• test_handle_site_created_respects_should_create_filter
• test_handle_site_deleted_skips_remove_for_checkout_form_base (regression)
• test_normalize_base_domain_handles_varied_inputs
  Two failures observed in Signup_Field_Site_Url_Test::test_to_fields_array_with_domain_selection
  and Site_Manager_Test::test_site_network_id reproduce identically on
  main (commit 1511f868) and are unrelated to this PR.

Related history

• 793057d2 — fix(checkout): use available_domains for auto-generated site URLs (fix(checkout): use available_domains for auto-generated site URLs #1072)
• 41ea2f23 — fix: site provisioning hardening — limitations, membership inference, domain promotion (fix: site provisioning hardening — limitations, membership inference, domain promotion #965)
• 702e0c58 — fix: auto-promote custom domain to primary on DNS verification (fix: auto-promote custom domain to primary on DNS verification for 3-part domains #991)
  #1072 made available_domains actually flow into the new site's
  domain column (good); this PR closes the matching gap on the
  Domain_Manager side so the alternate base is recognised as a shared
  network base, not a per-site mapping.

---

---

Merged via PR #1300 to main.
Merged by deterministic merge pass (pulse-wrapper.sh).

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aidevops.sh v3.20.1 spent 1m on this as a headless bash routine.