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+//! ## Validation
+//!
+//! 1. [Enumerated values](#enumerated-values)
+//! 2. [Validated values](#validated-values)
+//! 3. [Argument Relations](#argument-relations)
+//! 4. [Custom Validation](#custom-validation)
+//!
+//! An appropriate default parser/validator will be selected for the field's type. See
+//! [`value_parser!`][crate::value_parser!] for more details.
+//!
+//! ### Enumerated values
+//!
+//! If you have arguments of specific values you want to test for, you can use the
+//! [`PossibleValuesParser`][crate::builder::PossibleValuesParser] or [`Arg::value_parser(["val1",
+//! ...])`][crate::Arg::value_parser] for short.
+//!
+//! This allows you specify the valid values for that argument. If the user does not use one of
+//! those specific values, they will receive a graceful exit with error message informing them
+//! of the mistake, and what the possible valid values are
+//!
+//! ```rust
+#![doc = include_str!("../../examples/tutorial_builder/04_01_possible.rs")]
+//! ```
+#![doc = include_str!("../../examples/tutorial_builder/04_01_possible.md")]
+//!
+//! When enabling the [`derive` feature][crate::_features], you can use
+//! [`ValueEnum`][crate::ValueEnum] to take care of the boiler plate for you, giving the same
+//! results.
+//!
+//! ```rust
+#![doc = include_str!("../../examples/tutorial_builder/04_01_enum.rs")]
+//! ```
+#![doc = include_str!("../../examples/tutorial_builder/04_01_enum.md")]
+//!
+//! ### Validated values
+//!
+//! More generally, you can validate and parse into any data type with [`Arg::value_parser`].
+//!
+//! ```rust
+#![doc = include_str!("../../examples/tutorial_builder/04_02_parse.rs")]
+//! ```
+#![doc = include_str!("../../examples/tutorial_builder/04_02_parse.md")]
+//!
+//! A [custom parser][TypedValueParser] can be used to improve the error messages or provide additional validation:
+//!
+//! ```rust
+#![doc = include_str!("../../examples/tutorial_builder/04_02_validate.rs")]
+//! ```
+#![doc = include_str!("../../examples/tutorial_builder/04_02_validate.md")]
+//!
+//! See [`Arg::value_parser`][crate::Arg::value_parser] for more details.
+//!
+//! ### Argument Relations
+//!
+//! You can declare dependencies or conflicts between [`Arg`][crate::Arg]s or even
+//! [`ArgGroup`][crate::ArgGroup]s.
+//!
+//! [`ArgGroup`][crate::ArgGroup]s make it easier to declare relations instead of having to list
+//! each individually, or when you want a rule to apply "any but not all" arguments.
+//!
+//! Perhaps the most common use of [`ArgGroup`][crate::ArgGroup]s is to require one and *only* one
+//! argument to be present out of a given set. Imagine that you had multiple arguments, and you
+//! want one of them to be required, but making all of them required isn't feasible because perhaps
+//! they conflict with each other.
+//!
+//! ```rust
+#![doc = include_str!("../../examples/tutorial_builder/04_03_relations.rs")]
+//! ```
+#![doc = include_str!("../../examples/tutorial_builder/04_03_relations.md")]
+//!
+//! ### Custom Validation
+//!
+//! As a last resort, you can create custom errors with the basics of clap's formatting.
+//!
+//! ```rust
+#![doc = include_str!("../../examples/tutorial_builder/04_04_custom.rs")]
+//! ```
+#![doc = include_str!("../../examples/tutorial_builder/04_04_custom.md")]
+#![allow(unused_imports)]
+use crate::builder::*;
+
+pub use super::chapter_2 as previous;
+pub use super::chapter_4 as next;
+pub use crate::_tutorial as table_of_contents;