try-lazy-init

This is a straightforward fork of the lazy-init, with fallible initialisation added that I couldn't provide with a wrapper.

Installation

Please use cargo-edit to always add the latest version of this library:

cargo add try-lazy-init

Example

use try_lazy_init::{Lazy, LazyTransform};

let lazy = Lazy::new();
assert_eq!(
  // Not yet initialized, so this closure runs:
  lazy.get_or_create(|| 1),
  &1
);
assert_eq!(
  // Already initialized so this closure doesn't run:
  lazy.try_get_or_create(|| { unreachable!(); Err(()) }),
  Ok(&1)
);
assert_eq!(lazy.get(), Some(&1));
assert_eq!(lazy.into_inner(), Some(1));

let lazy_transform = LazyTransform::new(1);
assert_eq!(
  // Not yet initialized, so this closure runs:
  lazy_transform.get_or_create(|x| x + 1),
  &2
);
assert_eq!(
  // Only available `where T: Clone`.
  // Already initialized so this closure doesn't run:
  lazy_transform.try_get_or_create(|_| { unreachable!(); Err(()) }),
  Ok(&2)
);
assert_eq!(
  // Available also without `where T: Clone`.
  // Already initialized so this closure doesn't run:
  lazy_transform.get_or_create_or_poison(|_| { unreachable!(); Err(()) }),
  Ok(&2)
);
assert_eq!(lazy_transform.get(), Some(&2));
assert_eq!(lazy_transform.into_inner(), Ok(2));

let lazy_transform_2 = LazyTransform::<_, ()>::new(1);
assert_eq!(
  // This poisons by error, which won't panic this method or `.try_into_inner`:
  lazy_transform_2.get_or_create_or_poison(|_| Err(())),
  Err(Some(()))
);
assert_eq!(
  // The original value is now gone:
  lazy_transform_2.try_into_inner(),
  Err(None)
);

License

As of 2021-09-05 (i.e. the date of the fork), lazy-init's Cargo.toml states license = "Apache-2.0/MIT" while only the MIT License's text is present in LICENSE. I've left this situation unchanged.

As such, consider the package MIT-licensed for use and Apache-2.0/MIT dual-licensed when contributing.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Code of Conduct

Changelog

Versioning

try-lazy-init strictly follows Semantic Versioning 2.0.0 with the following exceptions:

• The minor version will not reset to 0 on major version changes (except for v1).
  Consider it the global feature level.
• The patch version will not reset to 0 on major or minor version changes (except for v0.1 and v1).
  Consider it the global patch level.

This includes the Rust version requirement specified above.
Earlier Rust versions may be compatible, but this can change with minor or patch releases.

Which versions are affected by features and patches can be determined from the respective headings in CHANGELOG.md.