Struct Cycles 

pub struct Cycles<'g> { /* private fields */ }

Contains information about dependency cycles in feature graphs.

Cargo permits cycles if at least one of the links is dev-only. Cycles exposes information about such dependencies.

Constructed through PackageGraph::cycles.

Implementations

impl<'g> Cycles<'g>

pub fn is_cyclic<'a>( &self, a: impl Into<FeatureId<'a>>, b: impl Into<FeatureId<'a>>, ) -> Result<bool, Error>

Returns true if a and b lie on a common directed cycle in the feature graph.

“Lie on a common cycle” means: in the same Strongly Connected Component and that SCC is non-trivial.

• For distinct feature IDs, that’s the same as being in a multi-node SCC.
• For the same feature ID, the node must either be in a multi-node SCC, or have a self-loop edge in the dependency graph (e.g., from a path dev-dependency on the package’s own crate).

In particular, is_cyclic(a, a) is not reflexively true: it returns false for features that aren’t on any cycle.

pub fn all_cycles( &self, ) -> impl Iterator<Item = Vec<FeatureId<'g>>> + 'g + use<'g>

Returns all the cyclic Strongly Connected Components of this graph: every multi-node SCC, plus every single-node SCC whose feature has a self-loop edge.

Cycles are returned in topological order: if features in cycle B depend on features in cycle A, A is returned before B.

Within a cycle, nodes are returned in non-dev order: if feature Foo has a dependency on Bar, and Bar has a dev-dependency on Foo, then Foo is returned before Bar.