Task 956 — Allow renaming a custom field (name) in the modern cfields edit modals

Issue: #956 Status: IMPLEMENTED & VERIFIED (2026-09-23) — branch task/issue-956

The gap

The legacy custom field edit form lets the user change the field name even when editing an existing field:

• gui/templates/dashio/cfields/cfieldsEdit.tpl:83-89 — cf_name is a plain editable text box (<input ... name="cf_name" ... value="{$gui->cfield.name|escape}">), no read-only attribute in edit mode.
• lib/cfields/cfieldsEdit.php:367-381 (doUpdate) — before saving it re-checks uniqueness with name_is_unique($id, $name); a rename that collides with an existing name is rejected with lang_get('cf_name_exists') ("Custom field name already exists. Please choose a new one"). Create has the same guarded check (cfieldsEdit.php:311-334).

The modern screens blocked renaming entirely:

• gui/templates/cfields/cfieldsView.html:318 — $('#editName').val(cf.name) .prop('readonly', true) forced the Name input read-only in the edit modal.
• gui/templates/cfields/cfieldsAssignView.html:251 — the same .prop('readonly', true) in the Assign screen's edit modal (reachable from the Assigned/Available name links).

Meanwhile the modern BFF PUT /api/cfields/{id} (api/cfields/index.php:268-274) already implemented the uniqueness guard and supported a changed name — the front-end gate was the only thing in the way.

Measured gap (browser DOM before the fix): editing the "Deployment" field returned {"modalVisible":true,"readonly":true,"name":"Deployment",...} — #editName.readOnly === true.

Implementation

BFF — api/cfields/index.php (Refs #956)

• PUT /{id} (update) — the duplicate-name 400 response now carries the machine-readable code: 'cf_name_exists' plus the legacy localized message lang_get('cf_name_exists', assignLocale()) instead of the raw English string (:268-278). This mirrors the pre-existing warning_no_type_change pattern so the front-ends can map the code onto the localized bundle text.
• POST / (create) — the same duplicate-name 400 now also returns code: 'cf_name_exists' + localized message (legacy doCreate surfaces lang_get('cf_name_exists') too, cfieldsEdit.php:311-334).

Screens — cfieldsView.html + cfieldsAssignView.html

• cfieldsView.html editCf() — removed the .prop('readonly', true) on #editName; the Name input is now a plain editable text box in edit mode, parity with the legacy cfieldsEdit.tpl:83-89.
• cfieldsAssignView.html editCf() — same removal: the Assign screen's edit modal can now rename fields too.
• Both saveCf() — the error handler maps resp.code === 'cf_name_exists' onto TLi18n.t('cf.msg.nameExists') (fallback resp.message / cf.msg.errorSave remain).

i18n

cf.msg.nameExists ("Custom field name already exists. Please choose a new one") added to all 10 bundles (gui/templates/i18n/{en,de,es,fr,it,ja,pt,ro,ru,zh}.json). Translations ported from the legacy $TLS_cf_name_exists in locale/*/strings.txt. All bundles validated with python3 -m json.tool.

Verification evidence (browser + API, fixture project id=1 + fields)

• Rename via cfieldsView edit modal: "Deployment" → "DeploymentPrime" editable, Save persisted the new name in custom_fields (label unchanged).
• Rename collision (cfieldsView): rename "Tier" → "DeploymentPrime" rejected, modal shows "Custom field name already exists. Please choose a new one"; switch to ?locale=ro shows "Numele campului personalizat există deja. Alegeți alt nume, vă rugăm." — localization works.
• Create collision (cfieldsView): Create with an existing name shows the same localized message.
• Assign screen: modal opened from the Assigned-table name link is editable (readonly:false); "Tier" → "TierY" persists to the DB and the table re-renders; collision rename shows the localized rejection and keeps the modal open.
• Browser console clean; inline JS node --check clean; php -l clean; all 10 bundles valid JSON.
• Event Viewer / events: only audit entries (log_level=16), 0 new Error/Warning rows.

Suite 956 in tmp/TLU_Test_Cases.md — 5/5 PASS.

Screenshots mirrored to docs/screenshots/ in the repo: issue-956-edit-modal-readonly-before.png, issue-956-edit-modal-editable.png, issue-956-rename-collision-rejected.png, issue-956-rename-support-after.png.

Refs #956.