MyModelView including a search limited to a field using syntax like `username:kootenpv`

model_view.py

# Authors: Leonid R. and Pascal van Kooten
from flask_admin.contrib.sqla import ModelView
from flask_admin.contrib.sqla import tools
from sqlalchemy import or_
from sqlalchemy.sql.expression import cast
from sqlalchemy import Unicode

class MyModelView(ModelView):

    # modifies existing _apply_search
    # https://github.com/flask-admin/flask-admin/blob/master/flask_admin/contrib/sqla/view.py#L874
    def _apply_search(self, query, count_query, joins, count_joins, search):
        """
            Apply search to a query.
        """
        terms = search.split(' ')

        for term in terms:
            if not term:
                continue

            #### this is the extra part ####

            if ":" in term:
                field_limit, term = term.split(":")
            else:
                field_limit, term = None, term

            ################################

            stmt = tools.parse_like_term(term)

            filter_stmt = []
            count_filter_stmt = []

            for field, path in self._search_fields:

                if field_limit and field_limit != field.name:
                    continue

                query, joins, alias = self._apply_path_joins(
                    query, joins, path, inner_join=False)

                count_alias = None

                if count_query is not None:
                    count_query, count_joins, count_alias = self._apply_path_joins(count_query,
                                                                                   count_joins,
                                                                                   path,
                                                                                   inner_join=False)

                column = field if alias is None else getattr(alias, field.key)
                filter_stmt.append(cast(column, Unicode).ilike(stmt))

                if count_filter_stmt is not None:
                    column = field if count_alias is None else getattr(count_alias, field.key)
                    count_filter_stmt.append(cast(column, Unicode).ilike(stmt))

            query = query.filter(or_(*filter_stmt))

            if count_query is not None:
                count_query = count_query.filter(or_(*count_filter_stmt))

        return query, count_query, joins, count_joins