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#![deny(missing_docs)] #![deny(missing_debug_implementations)] #![deny(intra_doc_link_resolution_failure)] #![cfg_attr(test, deny(warnings))] #![cfg_attr(not(feature = "std"), no_std)] //! # semval //! //! A lightweight and versatile toolbox for implementing semantic validation. //! //! Please refer to the bundled `reservation.rs` example to get an idea of how it works. //! //! Without any macro magic, at least not now. /// Invalidity context pub mod context; /// The crate's prelude /// /// A proposed set of imports to ease usage of this crate. pub mod prelude { pub use super::{ context::Context as ValidationContext, IntoValidated, Invalidity, IsValid, Result as ValidationResult, Validate, ValidatedFrom, ValidatedResult, }; } mod smallvec; mod util; use self::{context::Context, util::*}; use core::{any::Any, fmt::Debug, result::Result as CoreResult}; /// Result of a validation /// /// The result is `Ok` and empty if the validation succeeded. It is /// a validation context wrapped into `Err` that carries one or more /// invalidities. /// /// In contrast to common results the actual payload is carried by /// the error variant while a successful result is just the unit type. pub type Result<V> = UnitResult<Context<V>>; /// Invalidities that cause validation failures /// /// Validations fail if one or more objectives are considered invalid. /// These invalidity objectives are typically represented by sum types /// (`enum`) with one variant per objective. Some of the variants may /// recursively wrap an invalidity of a subordinate validation to trace /// back root causes. /// /// Implementations are required to implement `Debug` to enable analysis /// and low-level logging of those recursively wrapped sum types. /// /// The trait bound `Any` is implicitly implemented for most types and /// enables basic type inspection and downcasting for generically handling /// validation results though runtime reflection. pub trait Invalidity: Any + Debug {} impl<V> Invalidity for V where V: Any + Debug {} /// A trait for validating types /// /// Validation is expected to be an expensive operation that should /// only be invoked when crossing boundaries between independent /// components. pub trait Validate { /// Invalidity objectives type Invalidity: Invalidity; /// Perform the validation fn validate(&self) -> Result<Self::Invalidity>; } /// A utility trait for boolean validity checks. pub trait IsValid { /// Check if this instance is valid, discarding all further /// information why if not. fn is_valid(&self) -> bool; } impl<T> IsValid for T where T: Validate, { fn is_valid(&self) -> bool { self.validate().is_ok() } } /// Validate `Some` or otherwise implicitly evaluate to `Ok` /// in case of `None` /// /// If the absence of an optional value is considered a validation /// error this must be checked separately. impl<V> Validate for Option<V> where V: Validate, { type Invalidity = V::Invalidity; fn validate(&self) -> Result<Self::Invalidity> { if let Some(ref some) = self { some.validate() } else { Ok(()) } } } /// Result of a value-to-value conversion with post-validation of the output value pub type ValidatedResult<V> = CoreResult<V, (V, Context<<V as Validate>::Invalidity>)>; /// Value-to-value conversion with post-validation of the output value /// /// On success the output value is returned. On validation errors the output /// value is returned together with all invalidities. /// /// If validation of the output value has failed clients /// - may discard the output and abort, /// - are able to handle or fix the validation errors and continue, or /// - accept the output despite validation errors and continue. /// /// The initial value-to-value conversion from input to output must always succeed. /// /// The validation is performed on the output value after the input value has /// been consumed during the conversion. This *post-validation* approach should /// be applicable and sufficient for most use cases. It simplifies the validated /// result type by always returning the converted output independent of whether /// the validation succeeded or failed. /// /// # Example /// ``` /// # use semval::prelude::*; /// /// struct UnvalidatedEmail(String); /// /// struct Email(String); /// /// #[derive(Debug)] /// enum EmailInvalidity { /// MinLength, /// Format, /// } /// /// impl Validate for Email { /// type Invalidity = EmailInvalidity; /// # /// fn validate(&self) -> ValidationResult<Self::Invalidity> { /// // ...custom implementation... /// # ValidationContext::new() /// # .invalidate_if( /// # self.0.len() < 3, /// # EmailInvalidity::MinLength, /// # ) /// # .invalidate_if( /// # self.0.chars().filter(|c| *c == '@').count() != 1, /// # EmailInvalidity::Format, /// # ) /// # .into() /// } /// } /// /// impl ValidatedFrom<UnvalidatedEmail> for Email { /// fn validated_from(from: UnvalidatedEmail) -> ValidatedResult<Self> { /// // 1st step: Convert value /// let from = Email(from.0); /// // 2nd step: Validate converted value /// if let Err(err) = from.validate() { /// Err((from, err)) /// } else { /// Ok(from) /// } /// } /// } /// /// let unvalidated_email = UnvalidatedEmail("test@example.com".to_string()); /// match Email::validated_from(unvalidated_email) { /// Ok(email) => println!("Valid e-mail address: {}", email.0), /// Err((email, context)) => println!("Invalid e-mail address: {} {:?}", email.0, context), /// } /// ``` pub trait ValidatedFrom<T>: Validate + Sized { /// Convert input value into `Self` and validate `self` fn validated_from(from: T) -> ValidatedResult<Self>; } impl<T> ValidatedFrom<T> for T where T: Validate, { fn validated_from(from: T) -> ValidatedResult<Self> { if let Err(err) = from.validate() { Err((from, err)) } else { Ok(from) } } } /// Value-to-value conversion with post-validation of the output value /// /// Prefer to implement [ValidatedFrom](trait.ValidatedFrom.html) for types inside /// the current crate. All types that implement [ValidatedFrom](trait.ValidatedFrom.html) /// implicitly implement this trait. pub trait IntoValidated<V: Validate> { /// Convert `self` into output value and validate the output fn into_validated(self) -> ValidatedResult<V>; } impl<T, V> IntoValidated<V> for T where V: ValidatedFrom<T>, { fn into_validated(self) -> ValidatedResult<V> { V::validated_from(self) } } #[cfg(test)] mod tests { use super::*; struct AlwaysValid; impl Validate for AlwaysValid { type Invalidity = (); fn validate(&self) -> Result<Self::Invalidity> { Context::new().into() } } struct AlwaysInvalid; impl Validate for AlwaysInvalid { type Invalidity = (); fn validate(&self) -> Result<Self::Invalidity> { Context::new().invalidate(()).into() } } #[test] fn validate() { assert!(AlwaysValid.validate().is_ok()); assert!(AlwaysInvalid.validate().is_err()); } #[test] fn validate_option_none() { assert!((None as Option<AlwaysValid>).validate().is_ok()); assert!((None as Option<AlwaysInvalid>).validate().is_ok()); } #[test] fn validate_option_some() { assert!(Some(AlwaysValid).validate().is_ok()); assert!(Some(AlwaysInvalid).validate().is_err()); } #[test] fn validated_from() { assert!(AlwaysValid::validated_from(AlwaysValid).is_ok()); assert!(AlwaysInvalid::validated_from(AlwaysInvalid).is_err()); } #[test] fn into_validated() { assert!(IntoValidated::<AlwaysValid>::into_validated(AlwaysValid).is_ok()); assert!(IntoValidated::<AlwaysInvalid>::into_validated(AlwaysInvalid).is_err()); } #[test] fn is_valid() { assert!(AlwaysValid.is_valid()); assert!(!AlwaysInvalid.is_valid()); } }