feat(generic): fix and extend the columns selector

The column selector now gets initialized with the correct initial values
and it can now also cope with additional choices, like annotations and
the default table fields.
The `get_table_kwargs` method was updated to be able to show all the
selected columns.

Co-authored-by: Matthias Schlögl <matthias.schloegl@oeaw.ac.at>

Closes: #735

apis_core/generic/views.py

@@ -105,14 +105,39 @@ def get_table_class(self):
 
     def get_table_kwargs(self):
         kwargs = super().get_table_kwargs()
-        columns = self.request.GET.getlist("columns", [])
-        column_fields = [
-            field for field in self.model._meta.fields if field.name in columns
+
+        # we look at the selected columns and exclude
+        # all modelfields that are not part of that list
+        selected_columns = (
+            self.request.GET.getlist("columns")
+            if self.request.GET
+            else self.get_filterset(self.get_filterset_class()).form["columns"].initial
+        )
+        modelfields = self.model._meta.fields
+        kwargs["exclude"] = [
+            field.name for field in modelfields if field.name not in selected_columns
         ]
+
+        # now we look at the selected columns and
+        # add all modelfields and annotated fields that
+        # are part of the selected columns to the extra_columns
+        annotationfields = list()
+        for key, value in self.object_list.query.annotations.items():
+            fake_field = getattr(value, "field", value.output_field)
+            setattr(fake_field, "name", key)
+            annotationfields.append(fake_field)
+        extra_fields = list(
+            filter(
+                lambda x: x.name in selected_columns,
+                modelfields + tuple(annotationfields),
+            )
+        )
         kwargs["extra_columns"] = [
             (field.name, library.column_for_field(field, accessor=field.name))
-            for field in column_fields
+            for field in extra_fields
+            if field.name not in self.get_table_class().base_columns
         ]
+
         return kwargs
 
     def get_filterset_class(self):
@@ -122,21 +147,37 @@ def get_filterset_class(self):
         filterset_class = first_member_match(filterset_modules, GenericFilterSet)
         return filterset_factory(self.model, filterset_class)
 
+    def _get_columns_choices(self, columns_exclude):
+        # we start with the model fields
+        choices = [
+            (field.name, field.verbose_name) for field in self.model._meta.fields
+        ]
+        # we add any annotated fields to that
+        choices += [(key, key) for key in self.get_queryset().query.annotations.keys()]
+        # now we drop all the choices that are listed in columns_exclude
+        choices = list(filter(lambda x: x[0] not in columns_exclude, choices))
+        return choices
+
+    def _get_columns_initial(self, columns_exclude):
+        return [
+            field
+            for field in self.get_table().columns.names()
+            if field not in columns_exclude
+        ]
+
     def get_filterset(self, filterset_class):
         """
         We override the `get_filterset` method, so we can inject a
         `columns` selector into the form
         """
         filterset = super().get_filterset(filterset_class)
+        columns_exclude = filterset.form.columns_exclude
 
         # we inject a `columns` selector in the beginning of the form
         columns = forms.MultipleChoiceField(
             required=False,
-            choices=[
-                (field.name, field.verbose_name)
-                for field in self.model._meta.fields
-                if field.name not in filterset.form.columns_exclude
-            ]
+            choices=self._get_columns_choices(columns_exclude),
+            initial=self._get_columns_initial(columns_exclude),
         )
         filterset.form.fields = {**{"columns": columns}, **filterset.form.fields}