mitsuhiko/jinja2 — comment on commit 37303a86583eda14fb61b14b4922bdce073bce57
File:  line 0
By wallunit:

I also don't like the `plus` argument, because of that makes the choice whether to use the plus-variant or not up to the template author. But your application might require that all urls are quoted the same certain way.

In my opinion it would be appropriate to leave the implementation of that filter to the user, instead of providing a default implementation that either makes decisions (about the encoding and whether or not to use the plus-variant) for the user or requires them as argument, each time the filter is used.