MapItem::propertyDefinitions() claims it has a static value property, which is wrong

+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/MapItem.php
@@ -27,10 +27,20 @@ class MapItem extends FieldItemBase {
+    // Return the definitions for the currently set values.
+    $definitions = array();
+    foreach ($this->values as $name => $value) {

I'm not sure we should have that auto-generated values even? Once we'd have some static definitions they would be overwritten by what ever you set on the map, what seems wrong.

We could support defining some metadata for contained properties in the field settings + return them in static propertyDefinitions(). That would allow per instance definitions of contained properties while properly returning that from the field definition also.

I just got a form error due to cross- post. I was about to say it seems to prevent getting a stray "value" element serialized into the database when using this field type in a new content entity, so that's good, but an alternative to using the any type is to override toArray().

Obviously, you agree. This new patch looks good and also resolves the problem I see.

To clarify my comment, the kind of thing I was seeing without this patch when creating a content entity with a MapItem field was:

   'routeParameters' => 
  array (
    'node' => '3',
    'value' => NULL,
  ),

where the 'value' key should not be present.

oops, actually the code comments need some grammer and punctuations fixes.

I think this text is clearer.

simple docs fix

Changes look good, removed a superfluous empty line though.

thanks - just a blank line back to rtbc

per discussion with alexpott & berdir in IRC, just go back to the simple version since property_definitions is not used in core and should be documented and tested in a follow-up.

Follow-up issue: #2267733: Support field-specific property definitions for MapItem

Committed 78594ab and pushed to 8.x. Thanks!

This introduced a bug and should be rolled back: see #2887105: MapItem violates FieldItemInterface::schema()'s contract - breaks widgets.