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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift open source project
//
// Copyright (c) 2019 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
import Basics
import OrderedCollections
import PackageModel
/// A set of terms that are incompatible with each other and can therefore not
/// all be true at the same time. In dependency resolution, these are derived
/// from version requirements and when running into unresolvable situations.
public struct Incompatibility: Equatable, Hashable {
public let terms: OrderedCollections.OrderedSet<Term>
public let cause: Cause
public init(terms: OrderedCollections.OrderedSet<Term>, cause: Cause) {
self.terms = terms
self.cause = cause
}
public init(_ terms: Term..., root: DependencyResolutionNode, cause: Cause = .root) throws {
let termSet = OrderedCollections.OrderedSet(terms)
try self.init(termSet, root: root, cause: cause)
}
public init(_ terms: OrderedCollections.OrderedSet<Term>, root: DependencyResolutionNode, cause: Cause) throws {
if terms.isEmpty {
self.init(terms: terms, cause: cause)
return
}
// Remove the root package from generated incompatibilities, since it will
// always be selected.
var terms = terms
if terms.count > 1, cause.isConflict,
terms.contains(where: { $0.isPositive && $0.node == root })
{
terms = OrderedSet(terms.filter { !$0.isPositive || $0.node != root })
}
let normalizedTerms = try normalize(terms: terms.elements)
guard normalizedTerms.count > 0 else {
throw InternalError("An incompatibility must contain at least one term after normalization.")
}
self.init(terms: OrderedSet(normalizedTerms), cause: cause)
}
}
extension Incompatibility: CustomStringConvertible {
public var description: String {
let terms = self.terms
.map(String.init)
.joined(separator: ", ")
return "{\(terms)}"
}
}
public extension Incompatibility {
/// Every incompatibility has a cause to explain its presence in the
/// derivation graph. Only the root incompatibility uses `.root`. All other
/// incompatibilities are either obtained from dependency constraints,
/// decided upon in decision making or derived during unit propagation or
/// conflict resolution.
/// Using this information we can build up a derivation graph by following
/// the tree of causes. All leaf nodes are external dependencies and all
/// internal nodes are derived incompatibilities.
///
/// An example graph could look like this:
/// ```
/// ┌────────────────────────────┐ ┌────────────────────────────┐
/// │{foo ^1.0.0, not bar ^2.0.0}│ │{bar ^2.0.0, not baz ^3.0.0}│
/// └─────────────┬──────────────┘ └──────────────┬─────────────┘
/// │ ┌────────────────────────┘
/// ▼ ▼
/// ┌─────────────┴──────┴───────┐ ┌────────────────────────────┐
/// │{foo ^1.0.0, not baz ^3.0.0}│ │{root 1.0.0, not foo ^1.0.0}│
/// └─────────────┬──────────────┘ └──────────────┬─────────────┘
/// │ ┌───────────────────────────┘
/// ▼ ▼
/// ┌─────┴───┴──┐
/// │{root 1.0.0}│
/// └────────────┘
/// ```
indirect enum Cause: Equatable, Hashable {
public struct ConflictCause: Hashable {
public let conflict: Incompatibility
public let other: Incompatibility
}
/// The root incompatibility.
case root
/// The incompatibility represents a package's dependency on another
/// package.
case dependency(node: DependencyResolutionNode)
/// The incompatibility was derived from two others during conflict
/// resolution.
case conflict(cause: ConflictCause)
/// There exists no version to fulfill the specified requirement.
case noAvailableVersion
/// A version-based dependency contains unversioned-based dependency.
case versionBasedDependencyContainsUnversionedDependency(versionedDependency: PackageReference, unversionedDependency: PackageReference)
/// The package's tools version is incompatible.
case incompatibleToolsVersion(ToolsVersion)
public var isConflict: Bool {
if case .conflict = self { return true }
return false
}
/// Returns whether this cause can be represented in a single line of the
/// error output.
public var isSingleLine: Bool {
guard case .conflict(let cause) = self else {
assertionFailure("unreachable")
return false
}
return !cause.conflict.cause.isConflict && !cause.other.cause.isConflict
}
}
}
/// Normalize terms so that at most one term refers to one package/polarity
/// combination. E.g. we don't want both a^1.0.0 and a^1.5.0 to be terms in the
/// same incompatibility, but have these combined by intersecting their version
/// requirements to a^1.5.0.
private func normalize(terms: [Term]) throws -> [Term] {
let dict = try terms.reduce(into: OrderedCollections.OrderedDictionary<DependencyResolutionNode, (req: VersionSetSpecifier, polarity: Bool)>()) {
res, term in
// Don't try to intersect if this is the first time we're seeing this package.
guard let previous = res[term.node] else {
res[term.node] = (term.requirement, term.isPositive)
return
}
guard let intersection = term.intersect(withRequirement: previous.req, andPolarity: previous.polarity) else {
throw InternalError("""
Attempting to create an incompatibility with terms for \(term.node) \
intersecting versions \(previous) and \(term.requirement). These are \
mutually exclusive and can't be intersected, making this incompatibility \
irrelevant.
""")
}
res[term.node] = (intersection.requirement, intersection.isPositive)
}
return dict.map { Term(node: $0, requirement: $1.req, isPositive: $1.polarity) }
}
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