Struct FlagMeta 

pub struct FlagMeta<'a> { /* private fields */ }

What a flag knows about itself beyond how it parses.

Read it through the accessor methods. The fields are pub only because derived code builds this struct with a literal in the adopter’s crate; they are hidden from the docs because how they are laid out is not part of the API.

Implementations

impl FlagMeta<'_>

pub const EMPTY: FlagMeta<'static>

Metadata for a flag with nothing declared, for struct update syntax.

impl<'a> FlagMeta<'a>

Read access to every field, wherever it is stored.

Prefer these to the fields: a field can move between this struct and its cold extra half as tables are tuned for size, as 6.11.1 moved thirty-odd of them, and a getter keeps its name and type when that happens.

pub const fn flag(&self) -> &'a Flag<'a>

pub const fn builtin(&self) -> bool

A parser-supplied public entry point materialized in an exported spec.

It belongs in flag listings and completions, but not in the command synopsis where the runtime’s implicit help and version flags have never appeared.

pub const fn help(&self) -> Option<&'a str>

Short help, shown by -h.

pub const fn long_help(&self) -> Option<&'a str>

Long help, shown by --help.

pub const fn value_name(&self) -> Option<&'a str>

The placeholder for the flag’s value, such as n in --jobs <n>.

pub const fn env(&self) -> Option<&'a str>

pub const fn default(&self) -> &'a [&'a str]

pub const fn accepted_choices(&self) -> &'a [&'a str]

Canonical choices plus aliases accepted by the value type.

pub const fn choices(&self) -> &'a [&'a str]

pub const fn ignore_case(&self) -> bool

pub const fn allow_unknown_choices(&self) -> bool

Accept values outside choices while retaining the list for help and completion.

pub const fn required(&self) -> bool

pub const fn value_optional(&self) -> bool

Whether the flag’s value may be left off, as in --bump or --bump 5.

Help only, and deliberately: usage-lib’s parser refuses a bare --bump exactly as it refuses a bare --port, so this changes no binding — it changes the brackets, [BUMP] rather than <BUMP>, which is what a spec’s arg "[BUMP]" required=#false says. In FlagMeta and not in Flag for that reason: a parse never reads it.

pub const fn hide(&self) -> bool

pub const fn hide_default_value(&self) -> bool

pub const fn hide_env(&self) -> bool

pub const fn hide_possible_values(&self) -> bool

pub const fn hide_short_help(&self) -> bool

pub const fn hide_long_help(&self) -> bool

pub const fn count(&self) -> bool

Whether repetition is counted rather than collected, as in -vvv.

pub const fn complete( &self, ) -> Option<fn(&CompleteCtx<'_>) -> Vec<Candidate<'static>>>

What answers for this flag’s value when a shell asks.

The Rust counterpart of a spec’s run=: it is written into the emitted KDL as a command that asks this binary, so a spec stays complete for every other consumer while the binary answers itself.

pub const fn repeatable(&self) -> bool

Whether the flag may be given more than once. Distinct from Flag::variadic, which is one occurrence taking several values.

pub const fn help_heading(&self) -> Option<&'a str>

Heading to list this flag under in help output. Presentational: it groups a long flag list into sections and changes nothing about parsing.

pub const fn display_order(&self) -> Option<u32>

Explicit placement within its help section.

pub const fn hidden_shorts(&self) -> &'a [u8]

Short forms accepted by the parser but omitted from help and completion.

pub const fn hidden_longs(&self) -> &'a [&'a str]

Long forms accepted by the parser but omitted from help and completion.

pub const fn admonitions(&self) -> &'a [AdmonitionMeta<'a>]

Notes and warnings shown after the extended help text.

pub const fn deprecated(&self) -> Option<&'a str>

Why this flag is deprecated, plus optional release milestones.

pub const fn deprecated_warn_at(&self) -> Option<&'a str>

pub const fn deprecated_remove_at(&self) -> Option<&'a str>

pub const fn value_names(&self) -> &'a [&'a str]

Ordered placeholders for one fixed-arity occurrence.

pub const fn env_fallback(&self) -> &'a [&'a str]

pub const fn deprecated_env(&self) -> &'a [&'a str]

pub const fn choice_aliases(&self) -> &'a [(&'a str, &'a str)]

Canonical-to-alias pairs used when emitting a lossless spec.

pub const fn choice_details(&self) -> &'a [ChoiceMeta<'a>]

Per-canonical presentation metadata used when emitting a lossless spec.

pub const fn validate(&self) -> Option<&'a str>

Portable expr expression evaluated for each raw value.

pub const fn validate_error(&self) -> Option<&'a str>

Message reported when validation returns false.

pub const fn hide_env_values(&self) -> bool

pub const fn complete_type(&self) -> Option<&'a str>

A built-in completion class such as path or dir.

pub const fn var_min(&self) -> Option<u32>

pub const fn var_max(&self) -> Option<u32>

pub const fn value_var_min(&self) -> Option<u32>

Bounds on values consumed by one occurrence, distinct from the flag-level occurrence bounds above.

pub const fn value_var_max(&self) -> Option<u32>

pub const fn overrides(&self) -> &'a [&'a str]

Flags this one displaces when both are given.

pub const fn conflicts(&self) -> &'a [&'a str]

Flags that cannot be given alongside this one.

Where overrides resolves a collision by letting the last flag win, this reports it: the combination has no meaning, so honouring one side silently would hide a mistake.

pub const fn delimiter(&self) -> Option<char>

The character one word is split on to make several values, as clap’s value_delimiter does. Only ever set where several values can land.

pub const fn exclusive(&self) -> bool

Whether this flag must be given on its own.

The whole-command form of conflicts: everything the command declares counts, positionals included.

pub const fn requires(&self) -> &'a [&'a str]

Flags that must also be given when this one is.

The positive form of conflicts, and the mirror image of required_if: the same rule written on the flag that imposes it rather than on the flag it lands on.

pub const fn requires_if(&self) -> &'a [RequiresIf<'a>]

Value-triggered requirements declared by this flag.

pub const fn default_if(&self) -> &'a [DefaultIf<'a>]

Defaults that apply when another flag is given.

pub const fn required_if(&self) -> &'a [&'a str]

Flags that make this one necessary.

pub const fn required_if_eq(&self) -> &'a [RequiredIfEq<'a>]

Selector/value conditions, any one of which makes this required.

pub const fn required_if_eq_all(&self) -> &'a [RequiredIfEq<'a>]

Selector/value conditions which must all match to make this required.

pub const fn required_unless(&self) -> &'a [&'a str]

Flags that make this one unnecessary.

pub const fn required_unless_all(&self) -> &'a [&'a str]

All selectors must be present to make this unnecessary.

pub const fn surface(&self) -> Option<&'a str>

Named audience or compatibility surface this flag belongs to.

pub const fn available_if(&self) -> &'a [&'a str]

Descriptive availability conditions; they do not affect parsing.

pub const fn effect(&self) -> Option<Effect>

Trait Implementations

impl<'a> Clone for FlagMeta<'a>

fn clone(&self) -> FlagMeta<'a>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<'a> Copy for FlagMeta<'a>

impl<'a> Debug for FlagMeta<'a>

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

Formats the value using the given formatter.