Add support for frozen fields

This adds to new fields to the BaseModelView: `allow_frozen_fields` and
`excluded_frozen_fields`. Setting `allow_frozen_fields` to True adds
another button to the create and the edit view which acts like
"Save and Add Another", but "freezes" the fields (i.e.,
doesn't reset their contents).

`excluded_frozen_fields` can be used to specify fields
which should always be cleared (e.g., password fields).

doc/api/mod_model.rst

@@ -17,6 +17,7 @@
                           form_widget_args, form_extra_fields,
                           form_ajax_refs, form_create_rules,
                           form_edit_rules,
+                          allow_frozen_fields, exclude_frozen_fields
                           page_size, can_set_page_size
 
         .. autoattribute:: can_create
@@ -55,6 +56,9 @@
         .. autoattribute:: form_create_rules
         .. autoattribute:: form_edit_rules
 
+        .. autoattribute:: allow_frozen_fields
+        .. autoattribute:: exclude_frozen_fields
+
         .. autoattribute:: action_disallowed_list
 
         .. autoattribute:: page_size

flask_admin/model/base.py

@@ -3,7 +3,7 @@
 import csv
 import mimetypes
 import time
-from typing import Optional, cast, Type
+from typing import Optional, cast, Type, List
 
 from math import ceil
 import inspect
@@ -749,6 +749,31 @@ class MyModelView(ModelView):
         Customized rules for the create form. Override `form_rules` if present.
     """
 
+    allow_frozen_fields = False
+    """
+        If true, renders an additional button in the create and edit form which
+        acts like "Save and Add Another", but keeps ("freezes") field contents
+        instead of clearing them.
+
+        Fields in `excluded_frozen_fields` will never be frozen.
+    """
+
+    excluded_frozen_fields: List[str] = []
+    """
+        If `allow_frozen_fields` is set to `True` and the user clicks on
+        the corresponding button, only fields whose name is not included
+        in this list will be frozen.
+
+        In other words, add any fields here which shall be cleared even if the user
+        clicks on "Save And Add Another (Freeze Fields)", such as password fields.
+
+        Example::
+
+            class MyModelView(BaseModelView):
+                excluded_frozen_fields = ('password', 'confirm_password')
+
+    """
+
     # Actions
     action_disallowed_list = ObsoleteAttr('action_disallowed_list',
                                           'disallowed_actions',
@@ -871,6 +896,10 @@ def _refresh_forms_cache(self):
         else:
             self.column_editable_list = {}
 
+        # Initialize frozen fields
+        if not hasattr(self, "_frozen_id"):
+            self._frozen_id = None
+
     def _refresh_filters_cache(self):
         self._filters = self.get_filters()
 
@@ -2124,10 +2153,22 @@ def create_view(self):
         if not self.can_create:
             return redirect(return_url)
 
-        form = self.create_form()
+        # handle frozen fields, coming from an edit form
+        existing_model = None
+        if self._frozen_id:
+            existing_model = self.get_one(self._frozen_id)
+            self._frozen_id = None
+
+        form = self.create_form(obj=existing_model)
         if not hasattr(form, '_validated_ruleset') or not form._validated_ruleset:
             self._validate_form_instance(ruleset=self._form_create_rules, form=form)
 
+        if existing_model is not None:
+            # we need to reset excluded frozen fields here.
+            for field in self.excluded_frozen_fields:
+                if field in form.data:
+                    getattr(form, field).data = ""
+
         if self.validate_form(form):
             # in versions 1.1.0 and before, this returns a boolean
             # in later versions, this is the model itself
@@ -2136,6 +2177,14 @@ def create_view(self):
                 flash(gettext('Record was successfully created.'), 'success')
                 if '_add_another' in request.form:
                     return redirect(request.url)
+                elif '_freeze_fields' in request.form and self.allow_frozen_fields:
+                    # we need to do is reset the excluded fields and then persist
+                    # the frozen fields.
+                    for field in self.excluded_frozen_fields:
+                        if field in form.data:
+                            getattr(form, field).data = ""
+                    self._frozen_id = self.get_pk_value(model)
+                    return redirect(request.url)
                 elif '_continue_editing' in request.form:
                     # if we have a valid model, try to go to the edit view
                     if model is not True:
@@ -2189,6 +2238,9 @@ def edit_view(self):
                 flash(gettext('Record was successfully saved.'), 'success')
                 if '_add_another' in request.form:
                     return redirect(self.get_url('.create_view', url=return_url))
+                elif '_freeze_fields' in request.form and self.allow_frozen_fields:
+                    self._frozen_id = self.get_pk_value(model)
+                    return redirect(self.get_url('.create_view', url=return_url))
                 elif '_continue_editing' in request.form:
                     return redirect(self.get_url('.edit_view', id=self.get_pk_value(model)))
                 else:

flask_admin/templates/bootstrap4/admin/lib.html

@@ -289,6 +289,9 @@ <h3>{{ text }}</h3>
   {% if admin_view.can_create %}
   <input name="_add_another" type="submit" class="btn btn-secondary" value="{{ _gettext('Save and Add Another') }}" />
   {% endif %}
+  {% if admin_view.can_create and admin_view.allow_frozen_fields %}
+  <input name="_freeze_fields" type="submit" class="btn btn-secondary" value="{{ _gettext('Save and Add Another (Freeze Fields)') }}" />
+  {% endif %}
   {% if admin_view.can_edit %}
   <input name="_continue_editing" type="submit" class="btn btn-secondary" value="{{ _gettext('Save and Continue Editing') }}" />
   {% endif %}

flask_admin/translations/de/LC_MESSAGES/admin.po

@@ -466,6 +466,11 @@ msgstr "Abbrechen"
 msgid "Save and Add Another"
 msgstr "Speichern und neuer Eintrag"
 
+#: ../flask_admin/templates/bootstrap2/admin/lib.html:263
+#: ../flask_admin/templates/bootstrap3/admin/lib.html:254
+msgid "Save and Add Another (Freeze Fields)"
+msgstr "Speichern und neuer Eintrag (Felder einfrieren)"
+
 #: ../flask_admin/templates/bootstrap2/admin/lib.html:259
 #: ../flask_admin/templates/bootstrap3/admin/lib.html:250
 msgid "Save and Continue Editing"