serde_with_macros v2.0.0-rc.0

Changed

• Make #[serde_as] behave more intuitive on Option<T> fields.

  The #[serde_as] macro now detects if a #[serde_as(as = "Option<S>")] is used on a field of type Option<T> and applies #[serde(default)] to the field.
  This restores the ability to deserialize with missing fields and fixes a common annoyance (#183, #185, #311, #417).
  This is a breaking change, since now deserialization will pass where it did not before and this might be undesired.

  The Option field and transformation are detected by directly matching on the type name.
  These variants are detected as Option.

  • Option
  • std::option::Option, with or without leading ::
  • core::option::Option, with or without leading ::

  If an existing default attribute is detected, the attribute is not applied again.
  This behavior can be suppressed by using #[serde_as(no_default)] or #[serde_as(as = "Option<S>", no_default)].