rails url_helper placing params where format should be

Question

I'm trying to get Rails generated _path methods to give me

/terms_and_conditions?utm_source=source&utm_campaign=pain#some_link

So I've tried the following in a controller:

utm_params = {"utm_source" => "sauce", "utm_campaign" => "pain"} # from params
redirect_to terms_and_conditions_path(utm_params.merge(anchor: 'some_link')

and I get this, with the anchor as a param:

/terms_and_conditions?anchor=some_link&utm_source=source&utm_campaign=pain

If I try

terms_and_conditions_path(utm_params, anchor: 'some_link')

I get the hash in place of format, instead of proper params (i.e. no ?):

/terms_and_conditions.utm_source=source&utm_campaign=pain#some_link

How am I supposed to pass params on AND add an anchor?

Answer 1

Well this is bonkers.

Looks like the problem is Hash vs HashWithIndifferentAccess; when you do params.to_h, you get a HashWithIndifferentAccess - which the url helpers don't treat like a Hash, and can't pull the anchor out of - so the anchor becomes part of the params.

params.to_hash gives you a "real" hash; merging anchor: 'blah' works as expected.

(note: originally, I thought it was because the keys were strings - but it was a red herring; HashWithIndifferentAccess#symbolize_keys returns a real hash)

At this point, I'd love to reference the autogenerated x_path api docs, but I'm pretty sure that just doesn't exist, and the code is to confusing to follow. Trial and error won the day here.