How to put field elements in fieldsets in filter config forms

I can't enable the test module.
Drupal\Component\Plugin\Exception\PluginNotFoundException: The "filter_fieldsets_example" plugin does not exist. in Drupal\Core\Plugin\DefaultPluginManager->doGetDefinition() (line 57 of /Library/WebServer/Documents/drupal8x/core/lib/Drupal/Component/Plugin/Discovery/DiscoveryTrait.php).

+++ b/core/modules/filter/src/FilterFormatEditForm.php
@@ -33,9 +33,39 @@ public function form(array $form, FormStateInterface $form_state) {
+    // "Flatten" submitted settings

Must be a period after this.

This should have tests.

I got this error too, when I go to this path: /node/add/my-custom-content
I applied this patch, but it does not work, I think because I did not submit any form.

I think the real issue is: every times we throw an exception, this issue occur. To know what is the exception, we can set 'args' to array() in Symfony\Component\Debug\Exception\FlattenException::setTrace(). After fixing the exception, this issue gone away.

I can confirm that the above patch lets the filter settings form submit again...

Scratch that - this breaks things which need to be nested, like checkbox arrays...

Also this only seems to fix edit - I get the error on Add too...

In FilterFormatFormBase, I did this to the submit:

    echo 'presave';
    $format->save();
    echo 'postsave';

This produces:

presave
Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 64 bytes) in /Users/nthompson/Sites/d8/drupal-8.0.0-beta4/core/vendor/symfony/debug/Symfony/Component/Debug/Exception/FlattenException.php on line 216

So The bug seems to be inside the format saving...

Drupal/Core/Config/Config.php

in the save() method there is a section for casting the value... This seems to be where a failure happens:

      foreach ($this->data as $key => $value) {
        echo "casting $key to : "; var_dump($value);
        $this->data[$key] = $this->castValue($key, $value);
      }
      echo 'done';

casting uuid to : string(36) "8105978f-4ac7-4351-9e00-00144ecc281a"
casting langcode to : string(2) "en"
casting status to : bool(true)
casting dependencies to : array(1) {
  ["module"]=>
  array(2) {
    [0]=>
    string(6) "editor"
    [1]=>
    string(14) "path_corrector"
  }
}
casting name to : string(10) "Basic HTML"
casting format to : string(10) "basic_html"
casting weight to : int(0)
casting filters to : array(10) {
  ["filter_html"]=>
  array(5) {
    ["id"]=>
    string(11) "filter_html"
    ["provider"]=>
    string(6) "filter"
    ["status"]=>
    bool(true)
    ["weight"]=>
    int(-50)
    ["settings"]=>
    array(3) {
      ["allowed_html"]=>
      string(106) "    
 
 <ul> <ol> <li> <dl> <dt> <dd> <h4> <h5> <h6> <p> <span> <img>"
      ["filter_html_help"]=>
      int(0)
      ["filter_html_nofollow"]=>
      int(0)
    }
  }
  ["filter_align"]=>
  array(5) {
    ["id"]=>
    string(12) "filter_align"
    ["provider"]=>
    string(6) "filter"
    ["status"]=>
    bool(true)
    ["weight"]=>
    int(-49)
    ["settings"]=>
    array(0) {
    }
  }
  ["filter_caption"]=>
  array(5) {
    ["id"]=>
    string(14) "filter_caption"
    ["provider"]=>
    string(6) "filter"
    ["status"]=>
    bool(true)
    ["weight"]=>
    int(-48)
    ["settings"]=>
    array(0) {
    }
  }
  ["filter_html_image_secure"]=>
  array(5) {
    ["id"]=>
    string(24) "filter_html_image_secure"
    ["provider"]=>
    string(6) "filter"
    ["status"]=>
    bool(true)
    ["weight"]=>
    int(-47)
    ["settings"]=>
    array(0) {
    }
  }
  ["filter_htmlcorrector"]=>
  array(5) {
    ["id"]=>
    string(20) "filter_htmlcorrector"
    ["provider"]=>
    string(6) "filter"
    ["status"]=>
    bool(true)
    ["weight"]=>
    int(-46)
    ["settings"]=>
    array(0) {
    }
  }
  ["editor_file_reference"]=>
  array(5) {
    ["id"]=>
    string(21) "editor_file_reference"
    ["provider"]=>
    string(6) "editor"
    ["status"]=>
    bool(true)
    ["weight"]=>
    int(-45)
    ["settings"]=>
    array(0) {
    }
  }
  ["filter_url"]=>
  array(5) {
    ["id"]=>
    string(10) "filter_url"
    ["provider"]=>
    string(6) "filter"
    ["status"]=>
    bool(false)
    ["weight"]=>
    int(-41)
    ["settings"]=>
    array(1) {
      ["filter_url_length"]=>
      string(2) "72"
    }
  }
  ["path_corrector"]=>
  array(5) {
    ["id"]=>
    string(14) "path_corrector"
    ["provider"]=>
    string(14) "path_corrector"
    ["status"]=>
    bool(true)
    ["weight"]=>
    int(-44)
    ["settings"]=>
    array(2) {
      ["tags"]=>
      array(2) {
        ["a"]=>
        int(0)
        ["img"]=>
        int(0)
      }
      ["string_replacements"]=>
      string(23) "example.com|example.org"
    }
  }
  ["filter_autop"]=>
  array(5) {
    ["id"]=>
    string(12) "filter_autop"
    ["provider"]=>
    string(6) "filter"
    ["status"]=>
    bool(false)
    ["weight"]=>
    int(-42)
    ["settings"]=>
    array(0) {
    }
  }
  ["filter_html_escape"]=>
  array(5) {
    ["id"]=>
    string(18) "filter_html_escape"
    ["provider"]=>
    string(6) "filter"
    ["status"]=>
    bool(false)
    ["weight"]=>
    int(-43)
    ["settings"]=>
    array(0) {
    }
  }
}
</pre>

We never get a <code>done
....

Processing uuid... Done
Processing langcode... Done
Processing status... Done
Processing dependencies... Done
Processing name... Done
Processing format... Done
Processing weight... Done
Processing filters... 

Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 72 bytes) in /Users/nthompson/Sites/d8/drupal-8.0.0-beta4/core/vendor/symfony/debug/Symfony/Component/Debug/Exception/FlattenException.php on line 221

It seems to be inside the "castValue" method in StorableConfigBase...

...
...
filters.filter_url.settings
string(6) "object"
filters.filter_url.settings.filter_url_length
string(6) "object"
filters.path_corrector
string(6) "object"
filters.path_corrector.id
string(6) "object"
filters.path_corrector.provider
string(6) "object"
filters.path_corrector.status
string(6) "object"
filters.path_corrector.weight
string(6) "object"
filters.path_corrector.settings
string(6) "object"
filters.path_corrector.settings.tags
string(6) "object"
filters.path_corrector.settings.tags.a

Seems to be dying when trying to get the element for the "a" checkbox in my modules form...

So all my debugging has led me back to Mapping.php as Garret has found originally.

In my case, the final item filters.path_corrector.settings.tags.a produces a NULL $element....

If I debug the class of $element at each step, then var_dump the element if there is no "get" method... I get this:

KEY: uuid 
KEY: langcode 
KEY: status 
KEY: dependencies 
KEY: dependencies.module 
Drupal\Core\Config\Schema\Mapping
KEY: dependencies.module.0 
Drupal\Core\Config\Schema\Mapping
Drupal\Core\Config\Schema\Sequence
KEY: dependencies.module.1 
Drupal\Core\Config\Schema\Mapping
Drupal\Core\Config\Schema\Sequence
KEY: name 
KEY: format 
KEY: weight 
KEY: filters 
KEY: filters.filter_html 
Drupal\Core\Config\Schema\Sequence
KEY: filters.filter_html.id 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html.provider 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html.status 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html.weight 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html.settings 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html.settings.allowed_html 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html.settings.filter_html_help 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html.settings.filter_html_nofollow 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_align 
Drupal\Core\Config\Schema\Sequence
KEY: filters.filter_align.id 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_align.provider 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_align.status 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_align.weight 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_align.settings 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_caption 
Drupal\Core\Config\Schema\Sequence
KEY: filters.filter_caption.id 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_caption.provider 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_caption.status 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_caption.weight 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_caption.settings 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html_image_secure 
Drupal\Core\Config\Schema\Sequence
KEY: filters.filter_html_image_secure.id 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html_image_secure.provider 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html_image_secure.status 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html_image_secure.weight 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_html_image_secure.settings 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_htmlcorrector 
Drupal\Core\Config\Schema\Sequence
KEY: filters.filter_htmlcorrector.id 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_htmlcorrector.provider 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_htmlcorrector.status 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_htmlcorrector.weight 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_htmlcorrector.settings 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.editor_file_reference 
Drupal\Core\Config\Schema\Sequence
KEY: filters.editor_file_reference.id 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.editor_file_reference.provider 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.editor_file_reference.status 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.editor_file_reference.weight 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.editor_file_reference.settings 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_url 
Drupal\Core\Config\Schema\Sequence
KEY: filters.filter_url.id 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_url.provider 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_url.status 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_url.weight 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_url.settings 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.filter_url.settings.filter_url_length 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
Drupal\Core\Config\Schema\Mapping
KEY: filters.path_corrector 
Drupal\Core\Config\Schema\Sequence
KEY: filters.path_corrector.id 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.path_corrector.provider 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.path_corrector.status 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.path_corrector.weight 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.path_corrector.settings 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
KEY: filters.path_corrector.settings.tags 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
Drupal\Core\Config\Schema\Sequence
KEY: filters.path_corrector.settings.tags.a 
Drupal\Core\Config\Schema\Sequence
Drupal\Core\Config\Schema\Mapping
Drupal\Core\Config\Schema\Sequence
object(Drupal\Core\TypedData\Plugin\DataType\String)#811 (5) {
  ["value":protected]=>
  array(2) {
    ["a"]=>
    int(0)
    ["img"]=>
    int(0)
  }
  ["definition":protected]=>
  object(Drupal\Core\TypedData\DataDefinition)#810 (1) {
    ["definition":protected]=>
    array(4) {
      ["type"]=>
      string(6) "string"
      ["label"]=>
      string(5) "Value"
      ["class"]=>
      string(45) "\Drupal\Core\TypedData\Plugin\DataType\String"
      ["definition_class"]=>
      string(37) "\Drupal\Core\TypedData\DataDefinition"
    }
  }
  ["name":protected]=>
  string(4) "tags"

So, for some reason, it's interpreting my "tags" array as a string?!

Ahh... I have a feeling this might be a "feature"...

https://api.drupal.org/api/drupal/core%21modules%21filter%21src%21Plugin...

It looks like FilterFormat's expect all settings to be strings. There doesn't seem to be anything in there to consider a filter format setting data type to be anything other that string.

EDIT: I got to this by looking in TypedConfigManager.php and when it gets a definition of a fomat, we see:

Array
(
    [type] => filter
    [label] => Filter
    [class] => \Drupal\Core\Config\Schema\Mapping
    [definition_class] => \Drupal\Core\TypedData\MapDataDefinition
    [mapping] => Array
        (
            [id] => Array
                (
                    [type] => string
                    [label] => ID
                )

            [provider] => Array
                (
                    [type] => string
                    [label] => Provider
                )

            [status] => Array
                (
                    [type] => boolean
                    [label] => Status
                )

            [weight] => Array
                (
                    [type] => integer
                    [label] => Weight
                )

            [settings] => Array
                (
                    [type] => filter_settings.[%parent.id]
                )

        )

)

Ahhh - I wonder if we need to define a schema for our format settings?!

https://api.drupal.org/api/drupal/core!modules!filter!config!schema!filt...

Ah ha!!! This is not a Drupal 8 bug - this is a documentation issue IMHO ;)

Filter Settings are (I believe) assumed to be Strings, unless you specify otherwise.

I have fixed this on Path Corrector by adding this to config/schema/path_corrector.schema.yml:

filter_settings.path_corrector:
  type: filter
  label: 'Path Corrector'
  mapping:
    tags:
      type: sequence:
      label: 'Tags'
      sequence:
        type: string
        label: 'Tag'
    string_replacements:
      type: string
      label: 'String Replacements'

My clue was when I saw filter_settings.[%parent.id] above... I ended up finding /core/modules/filter/config/schema/filter.schema.yml and saw that Filter HTML and Filter URL all define their own config schema.

Arguably, Drupal should handle this error better. Some kind of "incompatible DataType" or something - without a full on WSOD...

EDIT: This is pretty handy - https://www.drupal.org/node/1905070

I'm on my phone right now so can't get to the code easily... But checkout the Drupal 8 branch of Path Corrector.

TLDR is "yes" - you need to replicate quite a bit. In my case with the checkboxes I had to define that the checkboxes were a mapping and that each child would be a string.

Sequence, not mapping ;)

http://cgit.drupalcode.org/path_corrector/tree/config/schema/path_correc...