Structure field : Conflicting "fields" attribute/prop

[Daandelange]

Description

The structure field itself works great. But extending it, some unexpected behaviour happens. Context: I've been extending a structure field by overriding its fields prop to a custom value, to dynamically provide one column per language. Result: The structure throws an error because it tries to use the fields from the blueprint [aka $field->attr['fields']]. Undefined index: fields in file: /starterkit/kirby/config/fields/structure.php line: 162

Expected behavior
That the underlying structure field is able to use my changed fields prop. (Or rather expect the structure field not to have a fields prop, so I'm unable to over-ride it ? ).

Notes

• The structure's fields prop is initially required (structure-field), changing it to not required myself, I can expect it to crash. But relying on the prop instead of the blueprint attrs would make the structure field more re-useable.
• For this use case I could also go with dynamic blueprints but that's not the point.

Solving
Changing $this->attrs['fields'] to $this->fields solves the issue in kirby/config/fields/structure.php. https://github.com/getkirby/kirby/blob/351b6348348cf78aed9a65920358caf218473102/config/fields/structure.php#L163 Everywhere else, the structure field already uses the parsed props via $this->propName.
Only here the code directly uses the popName from the attrs. (is there a reason for this? do other fields have similar bottlenecks?) This solution would definitely make re-using the structure field easier.

To reproduce

• Install this plugin in a Kirby 3.6.0 or 3.6.1.1 site :

  <?php
  // site/plugins/autostructurefields/index.php
  Kirby::plugin('kirbybugs/autostructurefields', [
    'fields' => [
      'languagesstructure' => [
          'extends' => 'structure',
          'props' => [
              'label' => 'Translation Items',
              'help' => 'One value per language, as much as you\'d like !',
              'fields' => function(array $dummyValue=null){ // Note: parent::fields() is required, ours is not
                  $fields = [];
                  foreach($this->kirby()->languages() as $lang){
                    $fields['lang_'.$lang->code()]=[
                        'type'  => 'text',
                        'name'  => 'lang_'.$lang->code(),
                        'label' => $lang->name(),
                    ];
                  }
                  //$this->attrs['fields']=$fields; // <-- Solution 2: if you uncomment this, fields get parsed correctly
                  return $fields;
              },
          ],
      ],
      'fieldpropsdebugger' => [
          'extends' => 'structure',
          'props' => [
              'label' => 'Structure Props Debugger',
              'fields' => ['test'=>['label'=>'TestField','name'=>'test', 'type'=>'text']],
          ],
      ],
  ],
  ]);

  // site/plugins/autostructurefields/index.js
  panel.plugin("kirbybugs/autostructurefields", {
  fields: {
    languagesstructure: {
      extends: "k-structure-field",
    },
    fieldpropsdebugger: {
      extends: "k-structure-field",
      template: '<ul><li v-for="field in fields">Label: {{field.label}} - Name: {{field.name}} - Type: {{field.type}}</li></ul>',
    },
  },
  });

• Add these fields to any page blueprint :

  fields:
  auto:
    type: languagesstructure
      #fields:
      #  link:
      #    type: url
  dbug:
    type: fieldpropsdebugger

  1. Go to the corresponding panel page : The underlying structure shows the error message above.
     Here I expect the structure field to use my provided fields.
  2. Uncomment the fields part in the blueprint and reload the panel : As the attribute was initially required, providing it should make the underlying structure behave correctly. The field from the user blueprint is shown correctly.
     But I still expect to see the fields from my props.
  3. Choose one :
     • global solution: Try the solution above in structure.php. Everything works as expected.
     • case-by-case fix/hack: Apply Solution 2 (see in comment) Everything works as expected.

Edit: Whoops, I pasted the "fields part" in the js snippet. The code should work now, with clarified instructions.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[Daandelange]

Hello, I'd like to re-open this tiny issue, I'm still running into it (while there are multiple ways of bypassing this).

So the purpose of my request is to make the structure-field better re-useable. Unless you really need to use the user-provided attributes from the blueprint, I think it makes more sense to use $this->props['fields'] or $this->fields instead of $this->attrs['fields'] so the StructureField is easier to extend, with less redondant code. (see snippet below)

If other people are running into this issue, the easiest way I found is to add a form to your extended-structure-field's methods. This will also ensure compatibility with current Kirby version (3.8.3) and before.

Kirby::plugin('kirbybugs/staticstructure', [
  'extends' => 'structure',
  'props' => [
    // Make fields static or whatever
    'fields' => function($fields=[]){
      //$this->attrs['fields']=[...]; // Here you could eventually force the prop into the attrs so that the native methods.form picks the right one.
      return [ 'test'=>['label'=>'TestField','name'=>'test', 'type'=>'text'] ];
    },
  ],
  'methods' => [
    // Overrides structure-field::methods::form() which grabs the form from $this->attrs['fields'] which we can't override.
    // Until https://github.com/getkirby/kirby/issues/4107 is merged, and after this will still be needed this for compatibility with older kirby versions.
    'form' => function (array $values = []) { 
      return new Form([
        'fields' => $this->fields, // <-- only line changed
        'values' => $values,
        'model'  => $this->model
      ]);
    },
  ],
]);