Use inner expressions

SearchVector.py

class ConcatWords(Func):
    arg_joiner = " || ' ' || "
    template = '%(expressions)s'

class SearchVector(SearchVectorCombinable, Func):
    function = 'to_tsvector'
    _output_field = SearchVectorField()

    def __init__(self, *expressions, **extra):
        expressions = [ConcatWords(*[Coalesce(expression, Value('')) for expression in expressions])]
        config = extra.get('config')
        if hasattr(config, 'resolve_expression'):
            expressions.insert(0, config)
        elif config is not None:
            expressions.insert(0, Value(config))
        super(SearchVector, self).__init__(*expressions, **extra)
        weight = self.extra.get('weight')
        if weight is not None and not hasattr(weight, 'resolve_expression'):
            weight = Value(weight)
        self.weight = weight

    def as_sql(self, compiler, connection, function=None, template=None):
        if template is None:
            template = self.template
        sql, params = super(SearchVector, self).as_sql(compiler, connection, function=function, template=template)
        print(sql, params)
        extra_params = []
        if self.weight:
            weight_sql, extra_params = compiler.compile(self.weight)
            sql = 'setweight({}, {})'.format(sql, weight_sql)
        return sql, params + extra_params