/// <summary>
/// Entry point for the combination evalutation phase of the algorithm. The algorithm
/// combines forward checking [FC] (i.e. trying to eliminate future possible combinations to evaluate)
/// with Conflict-directed Back Jumping.
/// Based off the FC-CBJ algorithm described in Prosser's Hybrid
/// Algorithms for the Constraint Satisfaction Problem:
/// http://archive.nyu.edu/bitstream/2451/14410/1/IS-90-10.pdf
/// </summary>
/// <param name="groupedItems">The candidate enlistment items grouped by product.</param>
/// <param name="itemSorter">
/// Function supplied by the caller to sort items in preferred/priority order. 'Higher
/// priority' items should come *first* in the sort.
/// </param>
/// <param name="shouldRejectPairFunc">
/// Function supplied by the caller to determine whether two items are
/// compatible or not.
/// </param>
/// <param name="diagnosticOutput">
/// Used to provide partial solutions to be used for diagnostic messages.
/// </param>
/// <returns>The 'best' solution (if one exists). Null otherwise.</returns>
public static IEnumerable <T> FindSolution(IEnumerable <IEnumerable <T> > groupedItems,
IComparer <T> itemSorter,
Func <T, T, bool> shouldRejectPairFunc,
Action <IEnumerable <T> > diagnosticOutput)
{
var solver = new CombinationSolver <T>(groupedItems,
itemSorter,
shouldRejectPairFunc);
return(solver.FindSolution(diagnosticOutput));
}
/// <summary>
/// Resolve a package closure
/// </summary>
public IEnumerable <PackageIdentity> Resolve(PackageResolverContext context, CancellationToken token)
{
var stopWatch = new Stopwatch();
token.ThrowIfCancellationRequested();
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
// validation
foreach (var requiredId in context.RequiredPackageIds)
{
if (!context.AvailablePackages.Any(p => StringComparer.OrdinalIgnoreCase.Equals(p.Id, requiredId)))
{
throw new NuGetResolverInputException(String.Format(CultureInfo.CurrentCulture, Strings.MissingDependencyInfo, requiredId));
}
}
// convert the available packages into ResolverPackages
var resolverPackages = new List <ResolverPackage>();
// pre-process the available packages to remove any packages that can't possibly form part of a solution
var availablePackages = RemoveImpossiblePackages(context.AvailablePackages, context.RequiredPackageIds);
foreach (var package in availablePackages)
{
IEnumerable <PackageDependency> dependencies = null;
// clear out the dependencies if the behavior is set to ignore
if (context.DependencyBehavior == DependencyBehavior.Ignore)
{
dependencies = Enumerable.Empty <PackageDependency>();
}
else
{
dependencies = package.Dependencies ?? Enumerable.Empty <PackageDependency>();
}
resolverPackages.Add(new ResolverPackage(package.Id, package.Version, dependencies, package.Listed, false));
}
// Sort the packages to make this process as deterministic as possible
resolverPackages.Sort(PackageIdentityComparer.Default);
// Keep track of the ids we have added
var groupsAdded = new HashSet <string>(StringComparer.OrdinalIgnoreCase);
var grouped = new List <List <ResolverPackage> >();
// group the packages by id
foreach (var group in resolverPackages.GroupBy(e => e.Id, StringComparer.OrdinalIgnoreCase))
{
groupsAdded.Add(group.Key);
var curSet = group.ToList();
// add an absent package for non-targets
// being absent allows the resolver to throw it out if it is not needed
if (!context.RequiredPackageIds.Contains(group.Key, StringComparer.OrdinalIgnoreCase))
{
curSet.Add(new ResolverPackage(id: group.Key, version: null, dependencies: null, listed: true, absent: true));
}
grouped.Add(curSet);
}
// find all needed dependencies
var dependencyIds = resolverPackages.Where(e => e.Dependencies != null)
.SelectMany(e => e.Dependencies.Select(d => d.Id).Distinct(StringComparer.OrdinalIgnoreCase));
foreach (string depId in dependencyIds)
{
// packages which are unavailable need to be added as absent packages
// ex: if A -> B and B is not found anywhere in the source repositories we add B as absent
if (!groupsAdded.Contains(depId))
{
groupsAdded.Add(depId);
grouped.Add(new List <ResolverPackage>()
{
new ResolverPackage(id: depId, version: null, dependencies: null, listed: true, absent: true)
});
}
}
token.ThrowIfCancellationRequested();
// keep track of the best partial solution
var bestSolution = Enumerable.Empty <ResolverPackage>();
Action <IEnumerable <ResolverPackage> > diagnosticOutput = (partialSolution) =>
{
// store each solution as they pass through.
// the combination solver verifies that the last one returned is the best
bestSolution = partialSolution;
};
// Run solver
var comparer = new ResolverComparer(context.DependencyBehavior, context.PreferredVersions, context.TargetIds);
var sortedGroups = ResolverInputSort.TreeFlatten(grouped, context);
var solution = CombinationSolver <ResolverPackage> .FindSolution(
groupedItems : sortedGroups,
itemSorter : comparer,
shouldRejectPairFunc : ResolverUtility.ShouldRejectPackagePair,
diagnosticOutput : diagnosticOutput);
// check if a solution was found
if (solution != null)
{
var nonAbsentCandidates = solution.Where(c => !c.Absent);
if (nonAbsentCandidates.Any())
{
// topologically sort non absent packages
var sortedSolution = ResolverUtility.TopologicalSort(nonAbsentCandidates);
// Find circular dependency for topologically sorted non absent packages since it will help maintain cache of
// already processed packages
var circularReferences = ResolverUtility.FindFirstCircularDependency(sortedSolution);
if (circularReferences.Any())
{
// the resolver is able to handle circular dependencies, however we should throw here to keep these from happening
throw new NuGetResolverConstraintException(
String.Format(CultureInfo.CurrentCulture, Strings.CircularDependencyDetected,
String.Join(" => ", circularReferences.Select(package => $"{package.Id} {package.Version.ToNormalizedString()}"))));
}
// solution found!
stopWatch.Stop();
context.Log.LogMinimal(
string.Format(Strings.ResolverTotalTime, DatetimeUtility.ToReadableTimeFormat(stopWatch.Elapsed)));
return(sortedSolution.ToArray());
}
}
// no solution was found, throw an error with a diagnostic message
var message = ResolverUtility.GetDiagnosticMessage(bestSolution, context.AvailablePackages, context.PackagesConfig, context.TargetIds, context.PackageSources);
throw new NuGetResolverConstraintException(message);
}
public IEnumerable <PackageIdentity> Resolve(IEnumerable <PackageIdentity> targets, IEnumerable <PackageDependencyInfo> availablePackages, IEnumerable <PackageReference> installedPackages, CancellationToken token)
{
if (installedPackages != null)
{
_installedPackages = new HashSet <PackageIdentity>(installedPackages.Select(e => e.PackageIdentity), PackageIdentity.Comparer);
}
// find the list of new packages to add
_newPackageIds = new HashSet <string>(targets.Select(e => e.Id).Except(_installedPackages.Select(e => e.Id), StringComparer.OrdinalIgnoreCase), StringComparer.OrdinalIgnoreCase);
// validation
foreach (var target in targets)
{
if (!availablePackages.Any(p => StringComparer.OrdinalIgnoreCase.Equals(p.Id, target.Id)))
{
throw new NuGetResolverInputException(String.Format(CultureInfo.CurrentUICulture, Strings.MissingDependencyInfo, target.Id));
}
}
// validation
foreach (var installed in _installedPackages)
{
if (!availablePackages.Any(p => StringComparer.OrdinalIgnoreCase.Equals(p.Id, installed.Id)))
{
throw new NuGetResolverInputException(String.Format(CultureInfo.CurrentUICulture, Strings.MissingDependencyInfo, installed.Id));
}
}
// TODO: this will be removed later when the interface changes
foreach (var installed in _installedPackages)
{
if (!targets.Any(p => StringComparer.OrdinalIgnoreCase.Equals(p.Id, installed.Id)))
{
throw new NuGetResolverInputException("Installed packages should be passed as targets");
}
}
// Solve
var solver = new CombinationSolver <ResolverPackage>();
var comparer = new ResolverComparer(_dependencyBehavior, _installedPackages, _newPackageIds);
List <List <ResolverPackage> > grouped = new List <List <ResolverPackage> >();
var packageComparer = PackageIdentity.Comparer;
List <ResolverPackage> resolverPackages = new List <ResolverPackage>();
// convert the available packages into ResolverPackages
foreach (var package in availablePackages)
{
IEnumerable <PackageDependency> dependencies = null;
// clear out the dependencies if the behavior is set to ignore
if (_dependencyBehavior == DependencyBehavior.Ignore)
{
dependencies = Enumerable.Empty <PackageDependency>();
}
else
{
dependencies = package.Dependencies;
}
resolverPackages.Add(new ResolverPackage(package.Id, package.Version, dependencies));
}
// Sort the packages to make this process as deterministic as possible
resolverPackages.Sort(PackageIdentityComparer.Default);
// Keep track of the ids we have added
HashSet <string> groupsAdded = new HashSet <string>(StringComparer.OrdinalIgnoreCase);
// group the packages by id
foreach (var group in resolverPackages.GroupBy(e => e.Id, StringComparer.OrdinalIgnoreCase))
{
groupsAdded.Add(group.Key);
List <ResolverPackage> curSet = group.ToList();
// add an absent package for non-targets
// being absent allows the resolver to throw it out if it is not needed
if (!targets.Any(e => StringComparer.OrdinalIgnoreCase.Equals(e.Id, group.Key)))
{
curSet.Add(new ResolverPackage(group.Key, null, null, true));
}
grouped.Add(curSet);
}
// find all needed dependencies
var dependencyIds = resolverPackages.Where(e => e.Dependencies != null).SelectMany(e => e.Dependencies.Select(d => d.Id).Distinct(StringComparer.OrdinalIgnoreCase));
foreach (string depId in dependencyIds)
{
// packages which are unavailable need to be added as absent packages
// ex: if A -> B and B is not found anywhere in the source repositories we add B as absent
if (!groupsAdded.Contains(depId))
{
grouped.Add(new List <ResolverPackage>()
{
new ResolverPackage(depId, null, null, true)
});
}
}
var solution = solver.FindSolution(grouped, comparer, ShouldRejectPackagePair);
if (solution != null)
{
var nonAbsentCandidates = solution.Where(c => !c.Absent);
if (nonAbsentCandidates.Any())
{
var sortedSolution = TopologicalSort(nonAbsentCandidates);
return(sortedSolution.ToArray());
}
}
// no solution found
throw new NuGetResolverConstraintException(Strings.NoSolution);
}
