Webform Node and other entity references

It is probably also useful to see when any Webform Nodes exist but do not reference any webform. A report going in both directions is akin to a more proper Correspondence or Bijection graph, where we're trying to ensure each entity has a matching partner, a natural 1-to-1 mapping.

The basic information can be obtained, roughly, with a simple query like this:

SELECT `webform`.`webform_id`, `node__webform`.`entity_id` as node_id FROM `webform`
LEFT JOIN `node__webform` ON `node__webform`.`webform_target_id` = `webform`.`webform_id`
ORDER BY node_id;

But this only accounts for webforms that either have or don't have Webform Nodes, it doesn't account for Webform Nodes that don't link to webforms, or Webforms referenced by multiple Webform Nodes.

For a more complete picture, we need a more complex query:

-- Show pairs + orphans + cardinality checks in one result.
SELECT
  x.webform_id,
  x.node_id,
  CASE
    WHEN x.webform_id IS NULL THEN '1_NODE_WITHOUT_WEBFORM'
    WHEN x.node_id   IS NULL THEN '2_UNREFERENCED_WEBFORM'
    WHEN wn.cnt_nodes_for_form = 1 AND nw.cnt_forms_for_node = 1
         THEN '5_PAIRED_1_TO_1'
    WHEN wn.cnt_nodes_for_form > 1 THEN '3_FORM_REFERENCED_BY_MULTIPLE_NODES'
    WHEN nw.cnt_forms_for_node > 1 THEN '4_NODE_REFERENCES_MULTIPLE_FORMS'
    ELSE 'CHECK'
  END AS status,
  wn.cnt_nodes_for_form,
  nw.cnt_forms_for_node
FROM (
  -- A) all webforms, with their referencing node if any
  SELECT w.webform_id, n.entity_id AS node_id
  FROM webform AS w
  LEFT JOIN node__webform AS n
    ON n.webform_target_id = w.webform_id
   AND n.deleted = 0
  /* optionally constrain to the node bundle that should carry the field:
     AND n.bundle = 'webform_node' */
  UNION
  -- C) nodes whose field points to a webform id that doesn't exist
  SELECT w.webform_id, n.entity_id AS node_id
  FROM node__webform AS n
  LEFT JOIN webform AS w
    ON w.webform_id = n.webform_target_id
  WHERE w.webform_id IS NULL
    AND n.deleted = 0
  /* optionally: AND n.bundle = 'webform_node' */
) AS x
LEFT JOIN (
  -- count how many nodes reference each webform
  SELECT webform_target_id, COUNT(*) AS cnt_nodes_for_form
  FROM node__webform
  WHERE deleted = 0
  GROUP BY webform_target_id
) AS wn
  ON wn.webform_target_id = x.webform_id
LEFT JOIN (
  -- count how many webforms each node references (should be 0 or 1)
  SELECT entity_id, COUNT(*) AS cnt_forms_for_node
  FROM node__webform
  WHERE deleted = 0
  GROUP BY entity_id
) AS nw
  ON nw.entity_id = x.node_id
ORDER BY status, x.node_id, x.webform_id;

This is a great idea. It would be handy for tracking nodes and paragraphs that reference webforms.

I think it should be in a dedicated contrib module called something like webform_audit or webform_usage.

I might opt not to have a query build the report, but to track webform usage in a table when an entity is saved.

When saving an entity, review the field definitions to check for a webform reference field. If a webform reference field exists, then store the entity type, entity ID, field name, delta, and webform id in the webform_usage table. For paragraphs, you can also look up the main entity. I would store the delta just in case there is a multiple-value webform reference field.

BTW, I think the entity usage module has some support for webforms.
@see https://www.drupal.org/project/issues/entity_usage?text=webform&status=All →

I hope this helps.