Enum ValueOrigin 

#[non_exhaustive]
pub enum ValueOrigin {
    DefaultMissing,
    Env(String),
    Default,
    DefaultIf {
        selector: String,
        when: Option<String>,
    },
}

Where a value came from, when it did not come from the command line.

About the value, not the flag. --color typed bare with default_missing has a token for the flag and none for the value, and that distinction is the whole question a spec author is asking when they ask why --color came out always. Values that were typed are attributed to the token that carried them instead — see TokenRole::Value.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

DefaultMissing

A flag that takes a value was given without one, so the declaration supplied it: default_missing, or the empty tri-state a bare value_optional flag records. One variant for both, because from argv’s side the same thing happened — the flag was typed and the value was not.

Env(String)

An environment variable, named.

Named because a flag may list several — env, env_fallback and deprecated_env, folded together by SpecFlag::env_names — and “it came from the environment” does not say which declaration fired or which one to delete.

Default

A declared default, on the flag or on the flag’s argument.

Not two variants: the precedence between them is a spec-authoring oddity rather than a fact about the value, and usage lint is the place to complain about declaring both.

DefaultIf

A default_if whose condition matched, with the condition that decided it. The selector alone is ambiguous — several conditions may name it with different when values.

Fields

selector: String

when: Option<String>

Trait Implementations

impl Clone for ValueOrigin

fn clone(&self) -> ValueOrigin

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ValueOrigin

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for ValueOrigin

impl PartialEq for ValueOrigin

fn eq(&self, other: &ValueOrigin) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for ValueOrigin