Document changes to field_read_fields()

[NormPlum]

The field_read_fields() function has changed since Drupal 7. I just ported a module that used this function, and it didn't work due to changes in the information provided to and from it.

For example, the D7 code was:

foreach (field_read_fields(array('type' => 'entityreference', 'entity_type' => $instance['entity_type'])) as $field_name => $field_info) {
  $er_fields[$field_name] = $field_name;
}

whereas I had to change it to:

foreach (field_read_fields(array('type' => 'entityreference')) as $field_name => $field_info) {
  if ($field_info['settings']['target_type'] == 'node') {
    $er_fields[$field_name] = $field_name;
  }
}

as passing in 'entity_type' no longer works.
There are other changes too. The D7 documentation says:

Additionally, conditions on the 'entity_type' and 'bundle' columns from the 'field_config_instance' table are supported (select fields having an instance on a given bundle).

But this seems to no longer be the case.

I think the changes to this function need to be documented, as I couldn't find any change records for it: https://docs.backdropcms.org/change-records?keys=field_read_fields&field_impacts_value=All

[laryn]

@NormPlum Thanks for filing this -- I ran across something field_read_* related just recently as well and it's also a change that needs to be documented. I'm guessing these changes came in with config management way back when...