v1.0.0

Compare Source

More than 8 years after the first commit and almost 5 years after the 0.99.0
release, derive_more has finally reached its 1.0.0 release. This release
contains a lot of changes (including some breaking ones) to make it easier to
use the derives and make it possible to extend them without having to break
backwards compatibility again. There are five major changes that I would like
to call out, but there are many more changes that are documented below:

1. There is a new Debug derive that can be used to easily customize Debug
   formatting.
2. A greatly improved Display derive, which allows you to do anything that
   thiserror provides, but it works
   for any type not just errors. And by combining the Display derive with the
   Error and From derives, there shouldn't really be any need to use
   thiserror anymore (if you are missing a feature/behaviour from thiserror
   please report an issue).
3. Traits that can return errors now return a type that implements Error
   when an error occurs instead of a &'static str.
4. When using use derive_more::SomeTrait the actual trait is also imported
   not just the derive macro. This is especially useful for Error and
   Display
5. The docs are now rendered on docs.rs and are much better overall.

Breaking changes

• The minimum supported Rust version (MSRV) is now Rust 1.75.
• Add the std feature which should be disabled in no_std environments.
• All Cargo features, except std, are now disabled by default. The full
  feature can be used to get the old behavior of supporting all possible
  derives.
• The TryFrom, Add, Sub, BitAnd, BitOr, BitXor, Not and Neg
  derives now return a dedicated error type instead of a &'static str on
  error.
• The FromStr derive now uses a dedicated FromStrError error type instead
  of generating unique one each time.
• The Display derive (and other fmt-like ones) now uses
  #[display("...", (<expr>),*)] syntax instead of
  #[display(fmt = "...", ("<expr>"),*)], and #[display(bound(<bound>))]
  instead of #[display(bound = "<bound>")]. So without the double quotes
  around the expressions and bounds.
• The Debug and Display derives (and other fmt-like ones) now transparently
  delegate to the inner type when #[display("...", (<expr>),*)] attribute is
  trivially substitutable with a transparent call.
  (#​322)
• The DebugCustom derive is renamed to just Debug (gated now under a separate
  debug feature), and its semantics were changed to be a superset of std variant
  of Debug.
• The From derive doesn't derive From<()> for enum variants without any
  fields anymore. This feature was removed because it was considered useless in
  practice.
• The From derive now uses #[from(<types>)] instead of #[from(types(<types>))]
  and ignores field type itself.
• The Into derive now uses #[into(<types>)] instead of #[into(types(<types>))]
  and ignores field type itself.
• The Into derive now generates separate impls for each field whenever the #[into(...)]
  attribute is applied to it. (#​291)
• Importing a derive macro now also imports its corresponding trait.
• The Error derive is updated with changes to the error_generic_member_access
  unstable feature for nightly users. (#​200,
  #​294)
• The as_mut feature is removed, and the AsMut derive is now gated by the
  as_ref feature. (#​295)
• A top level #[display("...")] attribute on an enum now requires the usage
  of {_variant} to include the variant instead of including it at {}. The
  reason is that {} now references the first argument to the format string,
  just like in all other format strings. (#​377)

Added

• Add support captured identifiers in Display derives. So now you can use:
  #[display(fmt = "Prefix: {field}")] instead of needing to use
  #[display(fmt = "Prefix: {}", field)]
• Add FromStr derive support for enums that contain variants without fields.
  If you pass the name of the variant to from_str it will create the matching
  variant.
• Add #[unwrap(owned, ref, ref_mut)] attribute for the Unwrap derive.
  By using them, it is possible to derive implementations for the reference types as well.
  (#​206)
• Add TryUnwrap derive similar to the Unwrap derive. This one returns a Result and does not panic.
  (#​206)
• Add support for container format in Debug derive with the same syntax as Display derives.
  (#​279)
• derive_more::derive module exporting only macros, without traits.
  (#​290)
• Add support for specifying concrete types to AsRef/AsMut derives.
  (#​298)
• Add TryFrom derive for enums to convert from their discriminant.
  (#​300)
• #[inline] attributes to IsVariant and Debug implementations.
  (#​334
• Add #[track_caller] to Add, Mul, AddAssign and MulAssign derives
  (#​378

Changed

• The Constructor and IsVariant derives now generate const fn functions.
• Static methods derived by IsVariant are now marked #[must_use].
  (#​350)
• The Unwrap and IsVariant derives now generate doc comments.
• #[automatically_derived] is now emitted from all macro expansions. This
  should prevent code style linters from attempting to modify the generated
  code.
• Upgrade to syn 2.0.
• The Error derive now works in nightly no_std environments

Fixed

• Use a deterministic HashSet in all derives, this is needed for rust analyzer
  to work correctly.
• Use Provider API for backtraces in Error derive.
• Fix Error derive not working with const generics.
• Support trait objects for source in Error, e.g.
  Box<dyn Error + Send + 'static>
• Fix bounds on derived IntoIterator impls for generic structs.
  (#​284)
• Fix documentation of generated bounds in Display derive.
  (#​297)
• Hygiene of macro expansions in presence of custom core crate.
  (#​327)
• Fix documentation of generated methods in IsVariant derive.
• Make {field:p} do the expected thing in format strings for Display and
  Debug. Also document weirdness around Pointer formatting when using
  expressions, due to field variables being references.
  (#​381)