Incorrect "missing schema" error for widget settings, if widget has the same id as formatter / field type

I agree the schema looks correct. 🤔

However, the Config Inspector module does not contain the string missing schema anywhere. So it must come from \Drupal\Core\Config\Schema\SchemaCheckTrait::checkValue() which contains:

    if ($element instanceof Undefined) {
      return [$error_key => 'missing schema'];
    }

1. Can you please provide a config export of the config that triggers this error? Just paste the YAML here :) I bet that's where the problem is: the schema looks fine, but probably the config data itself is not.
2. You can do what I'd do too: put a breakpoint on the quoted line above and re-trigger the error, then observe how you get to that point!

Sure thing!

Here is the output, which LGTM ("field_icon.settings.packages" throws the error: "'packages' is not a supported key."):

uuid: bef6d86a-4328-4e29-a0a9-6f83b1de96d7
langcode: en
status: true
dependencies:
  config:
    - field.field.node.article.body
    - field.field.node.article.comment
    - field.field.node.article.field_icon
    - field.field.node.article.field_image
    - field.field.node.article.field_tags
    - image.style.thumbnail
    - node.type.article
  module:
    - comment
    - image
    - micon
    - path
    - text
_core:
  default_config_hash: ewbd6G2uX456-bgwseM2Q-KQG3RkASoyHmTh-XR3oLU
id: node.article.default
targetEntityType: node
bundle: article
mode: default
content:
  body:
    type: text_textarea_with_summary
    weight: 2
    region: content
    settings:
      rows: 9
      summary_rows: 3
      placeholder: ''
      show_summary: false
    third_party_settings: {  }
  comment:
    type: comment_default
    weight: 20
    region: content
    settings: {  }
    third_party_settings: {  }
  created:
    type: datetime_timestamp
    weight: 10
    region: content
    settings: {  }
    third_party_settings: {  }
  field_icon:
    type: string_micon
    weight: 121
    region: content
    settings:
      packages:
        fa: fa
    third_party_settings: {  }
  field_image:
    type: image_image
    weight: 1
    region: content
    settings:
      progress_indicator: throbber
      preview_image_style: thumbnail
    third_party_settings: {  }
  field_tags:
    type: entity_reference_autocomplete_tags
    weight: 3
    region: content
    settings:
      match_operator: CONTAINS
      match_limit: 10
      size: 60
      placeholder: ''
    third_party_settings: {  }
  path:
    type: path
    weight: 30
    region: content
    settings: {  }
    third_party_settings: {  }
  promote:
    type: boolean_checkbox
    weight: 15
    region: content
    settings:
      display_label: true
    third_party_settings: {  }
  status:
    type: boolean_checkbox
    weight: 120
    region: content
    settings:
      display_label: true
    third_party_settings: {  }
  sticky:
    type: boolean_checkbox
    weight: 16
    region: content
    settings:
      display_label: true
    third_party_settings: {  }
  title:
    type: string_textfield
    weight: 0
    region: content
    settings:
      size: 60
      placeholder: ''
    third_party_settings: {  }
  uid:
    type: entity_reference_autocomplete
    weight: 5
    region: content
    settings:
      match_operator: CONTAINS
      match_limit: 10
      size: 60
      placeholder: ''
    third_party_settings: {  }
hidden: {  }

You can do what I'd do too: put a breakpoint on the quoted line above and re-trigger the error, then observe how you get to that point!

Can't seem to get into the correct loop iteration without "steping over" a hundred times.

And this workaround:

Doesn't seem to trigger xdebug for some reason...

Ok, no idea what I was doing there yesterday...

So I put a breakpoint at the exact location you pinpointed me to. But it looks fine to me!

The key is correct: $key = "content.field_icon.settings.packages"

And the $this->schema variable also seems to hold the correct values:

and the schema definition looks good as well:

I really doubt, that the implementation of Drupal\Core\Config\Schema\ArrayElement::get(), which is inherited and used by the

$element = $this->schema->get($key);

call.
But I don't see anything else, that could lead to this? Am I missing something?