activeadmin / activeadmin / 5127

79%

Pull #4666

travis-ci

raise an error for bad filters instead of silently failing

Today I attempted to add a filter on a has-many-through association. The
UI was display nothing for my filter and AFAICS there was nothing
anywhere to tell me what the problem was.

After digging around I found that

    ActiveAdmin::Fitlers::FormBuilder#filter

simply fails quietly (returning nothing) if the type for a filter can't
be determined.

I have updated the method to raise an error instead.

Here is what failed for me (names changed):

I had this class:

```
    class Foo < ActiveRecord::Base
        has_many :bars, though: :something
    end
```

In the corresponding activeadmin resource I had this:

```
  filter :bars_id_in,
      collection: -> { Bar.all },
      as: :select, # <------- I needed to specify this
      multiple: true,
```

I needed to specify `:as`, but I had to dig into the code to figure this
out.

I have not written any specs for this. If this patch is "pre approved"
then I can write specs before you pull if desired.

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