field_value/3 conversion behaviour seems inconsistent

[schnittchen]

Hello,

I have an Ecto schema with a Money.Ecto.Type field and noticed the following:

When rendering a changeset from the schema without errors, field_value returns a Money struct.
In the presence of an error (on another field), it returns the value represented as a string like "0.80".
This broke a custom field render function of mine.

Note that the behaviour has been changed by upgrading ecto (!) from ref "52b354" to 2.1.4. Previously, field_value would always return Money structs.

The new behaviour is possibly desired, if so I would like to understand why.

[josevalim]

Are you sure only the Ecto version changed?

In any case, this behaviour is desired because in case of errors, you want to show what the user typed, and what the user typed may not be a valid type/struct, exactly in case of errors, so you need to be able to handle raw values in your input.

[schnittchen]

Yes, only ecto changed.

Thank you for clarifying! Hopefully others confused in the same way find this.