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|
//! Example Error Handling
//!
//! > This example demonstrates how to handle errors in Mingling, including custom error types and error rendering.
//!
//! Run:
//! ```bash
//! cargo run --manifest-path examples/example-error-handling/Cargo.toml --quiet -- hallo
//! cargo run --manifest-path examples/example-error-handling/Cargo.toml --quiet -- hello
//! cargo run --manifest-path examples/example-error-handling/Cargo.toml --quiet -- hello Alice
//! cargo run --manifest-path examples/example-error-handling/Cargo.toml --quiet -- hello MyBestFriendAlice
//! cargo run --manifest-path examples/example-error-handling/Cargo.toml --quiet -- hello Peter
//! ```
//!
//! Output:
//! ```plaintext
//! Command not found: "hallo"
//! No name provided
//! Name not available
//! Name too long: 17 > 10
//! Hello, Peter
//! ```
use mingling::prelude::*;
use std::io::Write;
// In Mingling, instead of using ? to propagate errors upward,
// errors are treated as branches that continue execution.
dispatcher!("hello", CMDHello => EntryHello);
// Define error types
pack!(ErrorNoNameProvided = ());
pack!(ErrorNameTooLong = u16);
pack!(ErrorNameNotAvailable = ());
// Define success type
pack!(ResultName = String);
// Pre-registered names
static VEC_REGISTERED_NAMES: &[&str] = &["Alice", "Bob", "Charlie", "David", "Eve"];
#[chain]
fn handle_hello(args: EntryHello) -> Next {
let Some(name) = args.inner.first().cloned() else {
// If no name is provided, pass ErrorNoNameProvided
return ErrorNoNameProvided::default().to_render();
};
if name.len() > 10 {
// If the name is too long, pass ErrorNameTooLong
return ErrorNameTooLong::new(name.len() as u16).to_render();
}
if VEC_REGISTERED_NAMES.contains(&name.as_str()) {
// If the name already exists, pass ErrorNameNotAvailable
return ErrorNameNotAvailable::default().to_render();
}
// If the name is valid, pass ResultName
ResultName::new(name).to_render()
}
/// Renders a successful greeting with the given name.
#[renderer]
fn render_result_name(name: ResultName) -> RenderResult {
let mut render_result = RenderResult::new();
writeln!(render_result, "Hello, {}", *name).ok();
render_result
}
/// Renders the error when no name is provided.
#[renderer]
fn render_error_no_name_provided(_: ErrorNoNameProvided) -> RenderResult {
let mut render_result = RenderResult::new();
writeln!(render_result, "No name provided").ok();
render_result
}
/// Renders the error when the name is already taken.
#[renderer]
fn render_error_name_not_available(_: ErrorNameNotAvailable) -> RenderResult {
let mut render_result = RenderResult::new();
writeln!(render_result, "Name not available").ok();
render_result
}
/// Renders the error when the name exceeds the maximum length.
#[renderer]
fn render_error_name_too_long(len: ErrorNameTooLong) -> RenderResult {
let mut render_result = RenderResult::new();
writeln!(render_result, "Name too long: {} > 10", *len).ok();
render_result
}
/// Renders the error when the dispatcher (subcommand) is not found.
#[renderer]
fn render_dispatcher_not_found(err: ErrorDispatcherNotFound) -> RenderResult {
let mut render_result = RenderResult::new();
writeln!(
render_result,
"Command not found: \"{}\"",
err.inner.join(" ")
)
.ok();
render_result
}
gen_program!();
fn main() {
let mut program = ThisProgram::new();
program.with_dispatcher(CMDHello);
program.exec_and_exit();
}
|
