Form Validation crashes on invalid values in decimal-fields

[mavuio]

Describe the bug

Form validation on an "for_update" form crashes with

** (Decimal.Error) : number parsing syntax: "x"

when passing a value for a decimal field which cannot be parsed to decimal (e.g. "x")

To Reproduce

error is triggered in call to Comp.not_equal? in AshPhoenix.Form.attributes_changed?/1
you can trigger the error standalone like this:

Comp.not_equal?(Elixir.Decimal.new("1.5"),"x")

Expected behavior

technically it is correct for Comp to fail when comparing apples and oranges.

But in this case i'd like attributes_changed?/1 to return true, because a change of attribute is present, although an invalid one.

the invalid format can then be catched later on and presents an "invalid value" message in the UI.

i solved it in my project by redefining Comparable.Comparable.Type.BitString.To.Decimal so that
comparing a decimal with a non-decimal always returns :gt

lib/my_app/my_decimal_comp.ex:

import Ash.Type.Comparable

defcomparable left :: Decimal, right :: BitString do
  case Decimal.cast(right) do
    :error -> :gt
    _ -> Decimal.compare(left, Ash.Type.Decimal.new(right))
  end
end

** Runtime **

• Ash version
  2.4.20

[zachdaniel]

Thanks for the detailed report! I think what we'll do is rescue any errors produced by comparing values, and assume they are unequal if one occurs :)

[zachdaniel]

Fix pushed to main, it will be in the next release.

[mavuio]

Thanks for the quick fix.

Have a great 2023 ! ( we all hope ;)