Struct Features 

pub struct Features {
    pub default: Vec<String>,
    pub features: BTreeMap<String, Vec<String>>,
}

[features] declarations for a package.

Feature names are stable identifiers. The default group lists which features are enabled by default; other entries declare individual features and what enabling them implies.

Each entry on the right-hand side of a feature is a string in one of three documented forms (parsed lazily into FeatureEntry by the feature resolver):

• "feature_name" — enables another local feature on the same package (transitive feature implication).
• "dep:dependency_name" — enables an optional Cabin package dependency declared by this package’s [dependencies] table.
• "dependency_name/feature_name" — requests a specific feature on a Cabin package dependency. If the dependency is optional, this form also enables it.

The on-disk shape stays a flat list of strings so older readers and the canonical metadata format remain byte-identical for packages that only use the local-feature form.

Fields

default: Vec<String>

Default features. Empty when there is no default entry in [features].

features: BTreeMap<String, Vec<String>>

Declared features and their implication lists. Stored as a BTreeMap so iteration is deterministic and output is stable.

Implementations

impl Features

pub fn new( default: Vec<String>, features: BTreeMap<String, Vec<String>>, ) -> Result<Self, ValidationError>

Convenience constructor for Package::new-style call sites.

Errors

Returns a ValidationError when the resulting feature set fails Features::validate (see that method for the specific conditions).

pub fn validate(&self) -> Result<(), ValidationError>

Validate identifier grammar, the reserved default key, internal references between local features, and local cycles. dep: / dep/feature entries are validated for grammar only; the feature resolver checks that the referenced dependency exists, that it is optional when dep: is used, and that the requested feature exists on the dependency package — those checks need the package graph and therefore happen one layer up.

Errors

Returns ValidationError::ReservedFeatureName when default is used as a declared feature, ValidationError::UnknownFeatureReference for a default or implication pointing at an undeclared local feature, ValidationError::InvalidFeatureEntry for a malformed implication entry, a cycle error from Self::detect_cycles, and any identifier grammar error from validating a feature name.

pub fn expand(&self, roots: &BTreeSet<String>) -> BTreeSet<String>

Expand a set of root feature names by transitive closure over the local features map. Caller is responsible for ensuring every root is a declared feature.

Entries that take the form dep:<name> or <dep>/<feature> are skipped: they are package-level effects, not local features, and are owned by the cross-package feature resolver.

Trait Implementations

impl Clone for Features

fn clone(&self) -> Features

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Features

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

Formats the value using the given formatter.

impl Default for Features

fn default() -> Features

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Features

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Features

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Features

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for Features

impl StructuralPartialEq for Features