Clean up Edit's PHP to make it more maintainable: Drupal 8-style in-place editor definitions

While debugging #1946950: Node's menu link removed when changing either title, date or author via in-place editing (also: fape.inc is unmaintainable), I became even more baffled by the absolute piece of spaghetti that fape.inc is. It's impossible to understand.

Frankly, every commit made by nod_ during his D7 backport sprint has made it less understandable (that's what extreme time pressure will do). There's now two codepaths, and it's not clear why that's necessary and what the differences are.

So, to make Edit module stable and to solve #1946950: Node's menu link removed when changing either title, date or author via in-place editing (also: fape.inc is unmaintainable), I'll have to try to make sense out of fape.inc and simplify it. Potentially even add tests. Only then it will become solvable.

There's too much to be done in this issue, so it makes sense to split this off to subissues. fape.inc clean-up and the problem with the node menu link being removed when changing title/date/author have been solved in one patch (because their problem spaces overlapped so much) over at #1946950-3: Node's menu link removed when changing either title, date or author via in-place editing (also: fape.inc is unmaintainable).

I completed a bunch of this today:

• #1968524: Edit module maintainability: Rename _edit_is_special_field() to _edit_is_extra_field()
• #1968724: Refactor includes/pages.inc to closely resemble Drupal 8's codebase: controllers, MetadataGenerator, EditorSelector, etc.

Only remaining thing: backport D8-style in-place editor definitions to D7.

That was wrong for a while now.

This.

Do we really want to backport D8-style in-place editor definitions to D7? That means classes implementing an interface rather than info hooks listing callbacks and an include file. Isn't what we have now more D7-like, and shouldn't we therefor keep it?

/**
 * Implements hook_edit_editor_info().
 *
 * @see Drupal 8's \Drupal\edit\Plugin\InPlaceEditorManager.
 * @see Drupal 8's \Drupal\edit\EditPluginInterface.
 */
function edit_edit_editor_info() {
  $editors = array();
  $path = drupal_get_path('module', 'edit');
  $editors['form'] = array(
    'compatibility check callback' => '_edit_editor_form_is_compatible',
    'metadata callback' => '_edit_editor_form_metadata',
    'attachments callback' => '_edit_editor_form_attachments',
    'file' => 'includes/editor.form.inc',
    'file path' => $path,
  );
  return $editors;
}

and

<?php

/**
 * @file
 * Defines the "plain text" in-place editor.
 *
 * @see Drupal 8's \Drupal\edit\Plugin\InPlaceEditor\PlainTextEditor.
 */

function _edit_editor_plain_text_is_compatible(array $instance, array $items) {
  $field = field_info_field($instance['field_name']);

  // This editor is incompatible with multivalued fields.
  $cardinality_allows = $field['cardinality'] == 1;
  // This editor is incompatible with processed ("rich") text fields.
  $no_text_processing = empty($instance['settings']['text_processing']);

  return $cardinality_allows && $no_text_processing;
}

function _edit_editor_plain_text_metadata(array $instance, array $items) {
  return array();
}

function _edit_editor_plain_text_attachments() {
  return array(
    'library' => array(
      array('edit', 'edit.inPlaceEditor.plainText'),
    ),
  );
}

versus

<?php

/**
 * @file
 * Contains \Drupal\edit\Plugin\InPlaceEditor\PlainTextEditor.
 */

namespace Drupal\edit\Plugin\InPlaceEditor;

use Drupal\edit\EditorBase;
use Drupal\edit\Annotation\InPlaceEditor;
use Drupal\Core\Field\FieldDefinitionInterface;

/**
 * Defines the plain text in-place editor.
 *
 * @InPlaceEditor(
 *   id = "plain_text"
 * )
 */
class PlainTextEditor extends EditorBase {

  /**
   * {@inheritdoc}
   *
   * @todo The processed text logic is too coupled to text fields. Figure out
   *   how to generalize to other textual field types.
   */
  function isCompatible(FieldDefinitionInterface $field_definition, array $items) {
    // This editor is incompatible with multivalued fields.
    if ($field_definition->getFieldCardinality() != 1) {
      return FALSE;
    }
    // This editor is incompatible with processed ("rich") text fields.
    elseif ($field_definition->getFieldSetting('text_processing')) {
      return FALSE;
    }
    else {
      return TRUE;
    }
  }

  /**
   * {@inheritdoc}
   */
  public function getAttachments() {
    return array(
      'library' => array(
        array('edit', 'edit.inPlaceEditor.plainText'),
      ),
    );
  }

}

#10: that's definitely true. OTOH, the code in these classes would in any case be pretty significantly different, because of the huge changes to Entity/Field API in D8. But it'd still be easier to map changes in D8 to changes in D7, so it might still be worthwhile.

This is a 1.0 blocker. Together with #2169401: Provide direct download link for the necessary custom build of CKEditor. It's blocked on #2169505: Clean up Edit's Plugin class names and file locations.

Done.

I even found a piece of dead code in the process.

http://drupalcode.org/project/edit.git/commit/58044ac