thing_matcher/
error.rs

1//! Error types for thing-matcher operations.
2//!
3//! The crate uses a single sum-type, [`MatchingError`], for every fallible
4//! operation, and a [`Result`] alias to keep call-sites concise.
5//!
6//! The matching engine itself is **infallible**: scoring two things always
7//! produces a [`crate::MatchResult`]. Errors arise from explicit validation
8//! steps such as [`crate::Thing::validate`].
9//!
10//! ## Example
11//!
12//! ```
13//! use thing_matcher::{MatchingError, Thing};
14//!
15//! let empty = Thing::builder().build();
16//! match empty.validate() {
17//!     Err(MatchingError::MissingField(msg)) => {
18//!         assert!(msg.contains("required"));
19//!     }
20//!     other => panic!("unexpected: {other:?}"),
21//! }
22//! ```
23
24use thiserror::Error;
25
26/// Result alias used throughout the crate.
27///
28/// Equivalent to `std::result::Result<T, MatchingError>`.
29///
30/// ```
31/// use thing_matcher::Result;
32/// fn doubled(x: i32) -> Result<i32> { Ok(x * 2) }
33/// assert_eq!(doubled(3).unwrap(), 6);
34/// ```
35pub type Result<T> = std::result::Result<T, MatchingError>;
36
37/// Errors that may be returned by thing-matcher operations.
38///
39/// The matching engine itself is infallible — scoring two things always
40/// produces a [`crate::MatchResult`]. The only fallible operation in the
41/// public surface today is [`crate::Thing::validate`], which returns
42/// [`MatchingError::MissingField`] when the primary `name` is absent.
43/// Configuration builders ([`crate::MatchConfig::default`], `strict`,
44/// `lenient`) are infallible.
45///
46/// The enum is `#[non_exhaustive]` so future fallible code paths can add
47/// variants without breaking SemVer for downstream pattern-matches.
48///
49/// ```
50/// use thing_matcher::MatchingError;
51///
52/// let e = MatchingError::MissingField("name".into());
53/// // `Display` is provided by `thiserror`.
54/// assert!(e.to_string().contains("Missing required field"));
55/// ```
56#[derive(Error, Debug)]
57#[non_exhaustive]
58pub enum MatchingError {
59    /// A required field was absent. Returned by [`crate::Thing::validate`].
60    #[error("Missing required field: {0}")]
61    MissingField(String),
62}
63
64#[cfg(test)]
65mod tests {
66    use super::*;
67
68    #[test]
69    fn missing_field_display() {
70        let e = MatchingError::MissingField("name".into());
71        assert_eq!(e.to_string(), "Missing required field: name");
72    }
73
74    #[test]
75    fn result_alias_resolves() {
76        fn make() -> Result<i32> {
77            Ok(42)
78        }
79        assert_eq!(make().unwrap(), 42);
80    }
81
82    #[test]
83    fn errors_are_send_and_sync() {
84        fn assert_send_sync<T: Send + Sync>() {}
85        assert_send_sync::<MatchingError>();
86    }
87}
thing_matcher/error.rs

thing_matcher/
error.rs
