[#2750] Add a convert_to_extras field to ExampleIDatasetFormPlugin

Add another custom field to ExampleIDatasetFormPlugin, one that uses
convert_to/from_extras instead of convert_to/from_tags.

I also had to make the plugin disable DefaultDatasetForm's
check_data_dict() because it breaks with the new three-stage dataset
creation when using convert_to_extras.

ckanext/example_idatasetform/plugin.py

@@ -75,6 +75,13 @@ def form_to_db_schema(self):
                     converters.convert_to_tags('country_codes')]
                 })
 
+        # Add our custom_test metadata field to the schema, this one will use
+        # convert_to_extras instead of convert_to_tags.
+        schema.update({
+                'custom_text': [validators.ignore_missing,
+                    converters.convert_to_extras]
+                })
+
         return schema
 
     def db_to_form_schema(self):
@@ -91,6 +98,12 @@ def db_to_form_schema(self):
                 validators.ignore_missing]
             })
 
+        # Add our custom_text field to the dataset schema.
+        schema.update({
+            'custom_text': [
+                converters.convert_from_extras, validators.ignore_missing]
+            })
+
         return schema
 
     def setup_template_variables(self, context, data_dict=None):
@@ -140,5 +153,8 @@ def package_form(self):
 
     def check_data_dict(self, data_dict, schema=None):
         ExampleIDatasetFormPlugin.num_times_check_data_dict_called += 1
-        return lib_plugins.DefaultDatasetForm.check_data_dict(self, data_dict,
-                schema)
+        # Disable DefaultDatasetForm's check_data_dict(), because it breaks
+        # with the new three-stage dataset creation when using
+        # convert_to_extras.
+        #return lib_plugins.DefaultDatasetForm.check_data_dict(self, data_dict,
+        #        schema)

ckanext/example_idatasetform/templates/package/snippets/package_metadata_fields.html

@@ -33,6 +33,8 @@
   </select>
 </div>
 
+{{ form.input('custom_text', label=_('Custom Text'), id='field-custom_text', placeholder=_('custom text'), value=data.custom_text, error=errors.custom_text, classes=['control-medium']) }}
+
 {#
 {% block custom_fields %}
   {% snippet 'snippets/custom_form_fields.html', extras=data.extras, errors=errors, limit=3 %}