diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/lib.rs | 63 |
1 files changed, 63 insertions, 0 deletions
@@ -122,3 +122,66 @@ macro_rules! warn { eprintln!($($fmt)+); }; } + +/// Require that an expression returns [`Result::Ok`] or [`Option::Some`]. +/// +/// This macro simplifies error handling when the [`Result::Err`] or +/// [`Option::None`] cases of a [`std::result::Result`] or an +/// [`std::option::Option`] result in logging an error and terminating the +/// program. +/// +/// When invoked with a [`std::result::Result`], the macro takes only 1 parameter +/// — the [`std::result::Result`] whose success case you require — and in the +/// case of `Err(v)` returns `v`. Otherwise the [`err!`] macro is called with +/// the format string `"{e}"` (with `e` being the error). +/// +/// Since [`std::option::Option`]s don’t return error values — simply returning +/// [`Option::None` ]— we can’t print a meaningful diagnostic message for you. +/// Therefore you the user also need to provide as additional arguments the same +/// parameters you would pass to an invokation of [`err!`]. +/// +/// # Panics +/// +/// Calls [`err!`] which may panic if it fails. +/// +/// # Examples +/// +/// Try to take a child process’ standard input and assign it to `ci`. If the +/// result of `stdin.take()` is [`Option::None` ]then print the given diagnostic +/// message and exit the program using [`err!`]. +/// +/// ``` +/// use cerm::require; +/// +/// let ci = require!( +/// child.stdin.take(), +/// "Failed to open stdin of “{}”", +/// cmd.to_string_lossy() +/// ); +/// ``` +/// +/// +/// Wait for a child process to terminate, and execute [`err!`] if the call to +/// `child.wait()` fails. Notice how because `child.wait()` returns a +/// [`std::result::Result`], we only specify one argument. +/// +/// ``` +/// use cerm::require; +/// +/// require!(child.wait()); +/// ``` +#[macro_export] +macro_rules! require { + ($e:expr) => { + match $e { + Ok(v) => v, + Err(e) => { err!("{e}"); }, + } + }; + ($e:expr, $($fmt:tt)+) => { + match $e { + Some(v) => v, + None => { err!($($fmt)+); }, + } + }; +} |