I added a changeset utility function raise_if_invalid_fields(changeset, fields).

For example:

changeset
|> validate_inclusion(:cardinal_direction, ["north", "east", "south", "west"])
|> raise_if_invalid_fields([:cardinal_direction])

As its name suggests, the function raises if one of the given fields was provided with an invalid value.

Motivation/use case:

Say you have a dropdown list from which a user may select a value (like a <select> element). If the change is not included in the list, what happened?
It’s either a bug in the application, or a script, a malicious user or bot that bypassed the form control inputs.

As the very first version of my application will definitely have bugs, I want to raise to make sure that I don’t miss such a bug (if it were a bug); because if I just add a changeset error, I will not be automatically alerted of the bug, and have to rely on the user to report such cases.

If scripts or bots are abusing my forms, I can just remove the function call and let the error in the changeset (you don’t want to let your application because of a user submit).

Just an idea. Any thoughts welcome:)

Added fetch_field(changeset, keys) and fetch_change(changeset, keys) (and their bang ! versions).

street = ChangesetHelpers.fetch_field!(account_changeset, [:user, :config, :address, :street])

Version 0.17 is released:

• dropped raise_if_invalid_fields/2

• added field_fails_validation?/3 and field_violates_constraint?/3

Use case: sometimes instead of returning changeset errors to the client, you want to return a specialized response for some of the errors that happened. This is especially useful for returning specialized GraphQL objects representing errors in some cases, instead of a set of generic changeset errors.

Example:

case Accounts.register_user(input) do
  # ...
  {:error, changeset} ->
    email_already_used? =
      ChangesetHelpers.field_fails_validation?(changeset, :email, :unsafe_unique)
      || ChangesetHelpers.field_violates_constraint?(changeset, :email, :unique)

    if email_already_used? do
      # ...
    else
      {:error, changeset}
    end
end