How to use AshPhoenix.Form.add_error/3?

What are you calling add_error/3 with? How did you construct the form?

From looking at the source it seems like it matches on the form type (e.g. %Phoenix.HTML.Form{}) and then on the form source (e.g. %Ash.Changeset{}) and delegates to the source’s add_error.

For a changeset, passing a string should be fine:

@doc """
  Adds an error to the changesets errors list, and marks the change as `valid?: false`.

  ## Error Data

  The given `errors` argument can be a string, a keyword list, a struct, or a list of any of the three.

  If `errors` is a keyword list, or a list of keyword lists, the following keys are supported in the keyword list:

  - `field` (atom) - the field that the error is for. This is required, unless `fields` is given.
  - `fields` (list of atoms) - the fields that the error is for. This is required, unless `field` is given.
  - `message` (string) - the error message
  - `value` (any) - (optional) the field value that caused the error
  """
  @spec add_error(t(), error_info() | [error_info()], Keyword.t()) :: t()
  @spec add_error(t(), term | String.t() | list(term | String.t())) :: t()
  def add_error(changeset, errors, path \\ [])

Great answer! I think likely the issue with it not displaying is around the error not being attached to a field in the form, and for that to happen, the error has to have a field/path attached to it.

The best way to make that happen is to provide a field, and optionally a path if the error is in a nested form. i.e

AshPhoenix.Form.add_error(form, field: :text, path: [:comments, 0], message: "can't do that")

Hi Zach, I’m new to both Ash and Elixir so I might be misunderstanding something, but it looks like the @doc and the name of the arguments for AshPhoenix.Form.add_error/3 do not match what you suggested.

def add_error(form, path, opts \\ [])
def add_error(%Phoenix.HTML.Form{} = form, path, opts) do
def add_error(form, error, opts) do

The second argument being path on the general case and the Phoenix.HTML.Form case and being error in the actual implementation looks confusing, especially since the function taking a path argument as I understand it, simply unwraps the underlying Ash.Form from the Phoenix form.source and delegates to the function taking error.

The @doc says

:path - The path to add the error to. If the error(s) already have a path, don’t specify a path yourself."

But you provided a keyword list, which as I understand it binds to the path/error argument, with opts being empty. Your path: [:comments, 0] being one item in your keyword list, but then the function actually looks for path in opts if opts[:path] do.

So maybe updating the doc/variable names or adding a @spec would help here.

Oops! You’re totally right! Technically a path can be specified in the options to the add_error function, or in the options to create the error itself.

The documentation of Ash.Changeset.add_error was updated recently to link to Ash.Error, so that issue is handled, but I will fix the AshPhoenix.Form error now

Fixed here: improvement: simplify setting valid on `AshPhoenix.Form.add_error/3` · ash-project/ash_phoenix@b136825 · GitHub