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//! Extension for [`std::option::Option`].
/// Extension methods for [`std::option::Option`].
pub trait OptionExt<T> {
/// Converts an `Option` to a `Result`.
///
/// Unlike the standard library,
/// the value of `Option` is treated as `Result::Err` instead of `Result::Ok`.
///
/// Arguments passed to `err_or` are eagerly evaluated;
/// if you are passing the result of a function call,
/// it is recommended to use [`OptionExt::err_or_else`], which is lazily evaluated.
///
/// ## Example
///
/// ```rust
/// use rs_std_ext::option::OptionExt;
///
/// assert_eq!(Some("err").err_or(0), Err("err"));
/// assert_eq!(None::<&str>.err_or(0), Ok(0));
/// ```
fn err_or<U>(self, ok: U) -> Result<U, T>;
/// Converts an `Option` to a `Result`.
///
/// Unlike the standard library,
/// the value of `Option` is treated as `Result::Err` instead of `Result::Ok`.
///
/// ## Example
///
/// ```rust
/// use rs_std_ext::option::OptionExt;
///
/// assert_eq!(Some("err").err_or_else(|| 0), Err("err"));
/// assert_eq!(None::<&str>.err_or_else(|| 0), Ok(0));
/// ```
fn err_or_else<U>(self, f: impl FnOnce() -> U) -> Result<U, T>;
/// Converts an `Option` to a `Result`.
///
/// Unlike the standard library,
/// the value of `Option` is treated as `Result::Err` instead of `Result::Ok`.
///
/// ## Example
///
/// ```rust
/// use rs_std_ext::option::OptionExt;
///
/// assert_eq!(Some("err").err_or_default::<usize>(), Err("err"));
/// assert_eq!(None::<&str>.err_or_default::<usize>(), Ok(0));
/// ```
fn err_or_default<U: Default>(self) -> Result<U, T>;
/// Returns `true` if the `Option` is a `None` or the value inside of it matches a predicate.
///
/// This is equivalent to `option.is_some_and(!f)`.
///
/// ## Example
///
/// ```rust
/// use rs_std_ext::option::OptionExt;
///
/// assert_eq!(None::<usize>.is_none_or(|&i| i == 2), true);
/// assert_eq!(Some(5).is_none_or(|&i| i == 2), false);
/// ```
#[deprecated = "Use `Option::is_none_or` (offered by std) instead."]
fn is_none_or(&self, f: impl FnOnce(&T) -> bool) -> bool;
/// Returns nothing, consuming the value contained.
///
/// ## Panics
///
/// Panics if the value is a `Some` with a custom panic message provided by `msg`.
///
/// ## Example
///
/// ```rust,should_panic
/// use rs_std_ext::option::OptionExt;
///
/// let x: Option<&str> = Some("10");
/// x.expect_none("fruits are healthy");// panics with `fruits are healthy`
/// ```
///
/// ## Recommended Message Style
///
/// See the documentation for [`Option::expect`][option_expect] for more information.
///
/// [option_expect]: std::option::Option#method.expect
fn expect_none(self, msg: &str);
/// Tap into an `Option` and modify its value.
///
/// This method captures the `Option` in order not to break the caller-chain.
///
/// ## Example
///
/// ```rust
/// use rs_std_ext::option::OptionExt;
///
/// let mut x: Option<String> = Some("4".into());
/// assert_eq!(x.tap_mut(|s| s.push('2')), Some("42".into()));
/// ```
fn tap_mut(self, f: impl FnOnce(&mut T)) -> Option<T>;
}
impl<T> OptionExt<T> for Option<T> {
fn err_or<U>(self, ok: U) -> Result<U, T> {
match self {
Some(t) => Err(t),
None => Ok(ok),
}
}
fn err_or_else<U>(self, f: impl FnOnce() -> U) -> Result<U, T> {
match self {
Some(t) => Err(t),
None => Ok(f()),
}
}
fn err_or_default<U: Default>(self) -> Result<U, T> {
match self {
Some(t) => Err(t),
None => Ok(U::default()),
}
}
fn is_none_or(&self, f: impl FnOnce(&T) -> bool) -> bool {
match self {
Some(t) => f(t),
None => true,
}
}
fn expect_none(self, msg: &str) {
if self.is_some() {
panic!("{}", msg)
}
}
fn tap_mut(mut self, f: impl FnOnce(&mut T)) -> Option<T> {
if let Some(val) = &mut self {
f(val)
}
self
}
}