Module pubgrub::solver

PubGrub version solving algorithm.

It consists in efficiently finding a set of packages and versions that satisfy all the constraints of a given project dependencies. In addition, when that is not possible, PubGrub tries to provide a very human-readable and clear explanation as to why that failed. Below is an example of explanation present in the introductory blog post about PubGrub

Because dropdown >=2.0.0 depends on icons >=2.0.0 and
  root depends on icons <2.0.0, dropdown >=2.0.0 is forbidden.

And because menu >=1.1.0 depends on dropdown >=2.0.0,
  menu >=1.1.0 is forbidden.

And because menu <1.1.0 depends on dropdown >=1.0.0 <2.0.0
  which depends on intl <4.0.0, every version of menu
  requires intl <4.0.0.

So, because root depends on both menu >=1.0.0 and intl >=5.0.0,
  version solving failed.

The algorithm is generic and works for any type of dependency system as long as packages (P) and versions (V) implement the Package and Version traits. Package is strictly equivalent and automatically generated for any type that implement Clone + Eq + Hash + Debug + Display.

API

let solution = resolve(&dependency_provider, package, version)?;

Where dependency_provider supplies the list of available packages and versions, as well as the dependencies of every available package by implementing the DependencyProvider trait. The call to resolve for a given package at a given version will compute the set of packages and versions needed to satisfy the dependencies of that package and version pair. If there is no solution, the reason will be provided as clear as possible.

Structs

• OfflineDependencyProvider
  A basic implementation of DependencyProvider.

Enums

• Dependencies
  An enum used by DependencyProvider that holds information about package dependencies. For each Package there is a set of versions allowed as a dependency.

Traits

• DependencyProvider
  Trait that allows the algorithm to retrieve available packages and their dependencies. An implementor needs to be supplied to the resolve function.

Functions

• resolve
  Main function of the library. Finds a set of packages satisfying dependency bounds for a given package + version pair.