Implementation of the conditional target dependency proposal

Sources/Build/BuildParameters.swift

@@ -86,6 +86,11 @@ public struct BuildParameters: Encodable {
     /// module to finish building.
     public var emitSwiftModuleSeparately: Bool
 
+    /// The current build environment.
+    public var buildEnvironment: BuildEnvironment {
+        BuildEnvironment(platform: currentPlatform, configuration: configuration)
+    }
+
     public init(
         dataPath: AbsolutePath,
         configuration: BuildConfiguration,

Sources/Build/BuildPlan.swift

@@ -76,7 +76,7 @@ extension BuildParameters {
     }
 
     /// The current platform we're building for.
-    fileprivate var currentPlatform: PackageModel.Platform {
+    var currentPlatform: PackageModel.Platform {
         if self.triple.isDarwin() {
             return .macOS
         } else if self.triple.isAndroid() {
@@ -88,7 +88,7 @@ extension BuildParameters {
 
     /// Returns the scoped view of build settings for a given target.
     fileprivate func createScope(for target: ResolvedTarget) -> BuildSettings.Scope {
-        return BuildSettings.Scope(target.underlyingTarget.buildSettings, boundCondition: (currentPlatform, configuration))
+        return BuildSettings.Scope(target.underlyingTarget.buildSettings, environment: buildEnvironment)
     }
 }
 
@@ -155,6 +155,11 @@ public final class ClangTargetBuildDescription {
     /// The build parameters.
     let buildParameters: BuildParameters
 
+    /// The build environment.
+    var buildEnvironment: BuildEnvironment {
+        buildParameters.buildEnvironment
+    }
+
     /// Path to the bundle generated for this module (if any).
     var bundlePath: AbsolutePath? {
         buildParameters.bundlePath(for: target)
@@ -1132,6 +1137,11 @@ public class BuildPlan {
     /// The build parameters.
     public let buildParameters: BuildParameters
 
+    /// The build environment.
+    private var buildEnvironment: BuildEnvironment {
+        buildParameters.buildEnvironment
+    }
+
     /// The package graph.
     public let graph: PackageGraph
 
@@ -1200,10 +1210,11 @@ public class BuildPlan {
             let swiftTarget = SwiftTarget(
                 testDiscoverySrc: src,
                 name: testProduct.name,
-                dependencies: testProduct.underlyingProduct.targets)
+                dependencies: testProduct.underlyingProduct.targets.map { .target($0, conditions: []) }
+            )
             let linuxMainTarget = ResolvedTarget(
                 target: swiftTarget,
-                dependencies: testProduct.targets.map(ResolvedTarget.Dependency.target)
+                dependencies: testProduct.targets.map { .target($0, conditions: []) }
             )
 
             let target = try SwiftTargetBuildDescription(
@@ -1238,7 +1249,7 @@ public class BuildPlan {
             for dependency in target.dependencies {
                 switch dependency {
                 case .target: break
-                case .product(let product):
+                case .product(let product, _):
                     if buildParameters.triple.isDarwin() {
                         BuildPlan.validateDeploymentVersionOfProductDependency(
                             product, forTarget: target, diagnostics: diagnostics)
@@ -1426,19 +1437,19 @@ public class BuildPlan {
     ) {
 
         // Sort the product targets in topological order.
-        let nodes = product.targets.map(ResolvedTarget.Dependency.target)
+        let nodes: [ResolvedTarget.Dependency] = product.targets.map { .target($0, conditions: []) }
         let allTargets = try! topologicalSort(nodes, successors: { dependency in
             switch dependency {
             // Include all the depenencies of a target.
-            case .target(let target):
-                return target.dependencies
+            case .target(let target, _):
+                return target.dependencies.filter { $0.satisfies(self.buildEnvironment) }
 
             // For a product dependency, we only include its content only if we
             // need to statically link it.
-            case .product(let product):
+            case .product(let product, _):
                 switch product.type {
                 case .library(.automatic), .library(.static):
-                    return product.targets.map(ResolvedTarget.Dependency.target)
+                    return product.targets.map { .target($0, conditions: []) }
                 case .library(.dynamic), .test, .executable:
                     return []
                 }
@@ -1453,7 +1464,7 @@ public class BuildPlan {
 
         for dependency in allTargets {
             switch dependency {
-            case .target(let target):
+            case .target(let target, _):
                 switch target.type {
                 // Include executable and tests only if they're top level contents
                 // of the product. Otherwise they are just build time dependency.
@@ -1477,7 +1488,7 @@ public class BuildPlan {
                     }
                 }
 
-            case .product(let product):
+            case .product(let product, _):
                 // Add the dynamic products to array of libraries to link.
                 if product.type == .library(.dynamic) {
                     linkLibraries.append(product)
@@ -1496,10 +1507,11 @@ public class BuildPlan {
 
     /// Plan a Clang target.
     private func plan(clangTarget: ClangTargetBuildDescription) {
-        for dependency in clangTarget.target.recursiveDependencies() {
-            switch dependency.underlyingTarget {
+        let recursiveBuildTargets = clangTarget.target.recursiveBuildTargetDependencies(in: buildEnvironment)
+        for targetDependency in recursiveBuildTargets {
+            switch targetDependency.underlyingTarget {
             case is SwiftTarget:
-                if case let .swift(dependencyTargetDescription)? = targetMap[dependency] {
+                if case let .swift(dependencyTargetDescription)? = targetMap[targetDependency] {
                     if let moduleMap = dependencyTargetDescription.moduleMap {
                         clangTarget.additionalFlags += ["-fmodule-map-file=\(moduleMap.pathString)"]
                     }
@@ -1510,7 +1522,7 @@ public class BuildPlan {
                 clangTarget.additionalFlags += ["-I", target.includeDir.pathString]
 
                 // Add the modulemap of the dependency if it has one.
-                if case let .clang(dependencyTargetDescription)? = targetMap[dependency] {
+                if case let .clang(dependencyTargetDescription)? = targetMap[targetDependency] {
                     if let moduleMap = dependencyTargetDescription.moduleMap {
                         clangTarget.additionalFlags += ["-fmodule-map-file=\(moduleMap.pathString)"]
                     }
@@ -1534,10 +1546,13 @@ public class BuildPlan {
     private func plan(swiftTarget: SwiftTargetBuildDescription) throws {
         // We need to iterate recursive dependencies because Swift compiler needs to see all the targets a target
         // depends on.
-        for dependency in swiftTarget.target.recursiveDependencies() {
-            switch dependency.underlyingTarget {
+        let recursiveBuildTargets = swiftTarget.target
+            .recursiveBuildDependencies(in: buildEnvironment)
+            .compactMap { $0.target }
+        for targetDependency in recursiveBuildTargets {
+            switch targetDependency.underlyingTarget {
             case let underlyingTarget as ClangTarget where underlyingTarget.type == .library:
-                guard case let .clang(target)? = targetMap[dependency] else {
+                guard case let .clang(target)? = targetMap[targetDependency] else {
                     fatalError("unexpected clang target \(underlyingTarget)")
                 }
                 // Add the path to modulemap of the dependency. Currently we require that all Clang targets have a

Sources/Build/ManifestBuilder.swift

@@ -36,6 +36,7 @@ public class LLBuildManifestBuilder {
 
     var buildConfig: String { buildParameters.configuration.dirname }
     var buildParameters: BuildParameters { plan.buildParameters }
+    var buildEnvironment: BuildEnvironment { buildParameters.buildEnvironment }
 
     /// Create a new builder with a build plan.
     public init(_ plan: BuildPlan) {
@@ -268,12 +269,12 @@ extension LLBuildManifestBuilder {
             }
         }
 
-        for dependency in target.target.dependencies {
+        for dependency in target.target.buildDependencies(in: buildEnvironment) {
             switch dependency {
-            case .target(let target):
+            case .target(let target, _):
                 addStaticTargetInputs(target)
 
-            case .product(let product):
+            case .product(let product, _):
                 switch product.type {
                 case .executable, .library(.dynamic):
                     // Establish a dependency on binary of the product.
@@ -368,12 +369,12 @@ extension LLBuildManifestBuilder {
             }
         }
 
-        for dependency in target.target.dependencies {
+        for dependency in target.target.buildDependencies(in: buildEnvironment) {
             switch dependency {
-            case .target(let target):
+            case .target(let target, _):
                 addStaticTargetInputs(target)
 
-            case .product(let product):
+            case .product(let product, _):
                 switch product.type {
                 case .executable, .library(.dynamic):
                     // Establish a dependency on binary of the product.

Sources/PackageDescription/BuildSettings.swift

@@ -45,7 +45,7 @@ public struct BuildConfiguration: Encodable {
 ///             .define("ENABLE_SOMETHING", .when(configuration: .release)),
 ///         ],
 ///         linkerSettings: [
-///             .linkLibrary("openssl", .when(platforms: [.linux])),
+///             .linkedLibrary("openssl", .when(platforms: [.linux])),
 ///         ]
 ///     ),
 public struct BuildSettingCondition: Encodable {
@@ -228,7 +228,7 @@ public struct SwiftSetting: Encodable {
     /// Use compilation conditions to only compile statements if a certain condition is true.
     /// For example, the Swift compiler will only compile the
     /// statements inside the `#if` block when `ENABLE_SOMETHING` is defined:
-    ///     
+    ///
     ///     #if ENABLE_SOMETHING
     ///        ...
     ///     #endif

Sources/PackageDescription/Package.swift

@@ -452,6 +452,7 @@ extension Target.Dependency: Encodable {
         case type
         case name
         case package
+        case condition
     }
 
     private enum Kind: String, Codable {
@@ -477,16 +478,19 @@ extension Target.Dependency: Encodable {
         }
       #else
         switch self {
-        case ._targetItem(let name):
+        case ._targetItem(let name, let condition):
             try container.encode(Kind.target, forKey: .type)
             try container.encode(name, forKey: .name)
-        case ._productItem(let name, let package):
+            try container.encode(condition, forKey: .condition)
+        case ._productItem(let name, let package, let condition):
             try container.encode(Kind.product, forKey: .type)
             try container.encode(name, forKey: .name)
             try container.encode(package, forKey: .package)
-        case ._byNameItem(let name):
+            try container.encode(condition, forKey: .condition)
+        case ._byNameItem(let name, let condition):
             try container.encode(Kind.byName, forKey: .type)
             try container.encode(name, forKey: .name)
+            try container.encode(condition, forKey: .condition)
         }
       #endif
     }

Sources/PackageDescription/Target.swift

@@ -37,9 +37,9 @@ public final class Target {
         case productItem(name: String, package: String?)
         case byNameItem(name: String)
       #else
-        case _targetItem(name: String)
-        case _productItem(name: String, package: String?)
-        case _byNameItem(name: String)
+        case _targetItem(name: String, condition: BuildSettingCondition?)
+        case _productItem(name: String, package: String?, condition: BuildSettingCondition?)
+        case _byNameItem(name: String, condition: BuildSettingCondition?)
       #endif
     }
 
@@ -599,11 +599,12 @@ extension Target.Dependency {
     ///
     /// - parameters:
     ///   - name: The name of the target.
+    @available(_PackageDescription, obsoleted: 999)
     public static func target(name: String) -> Target.Dependency {
       #if PACKAGE_DESCRIPTION_4
         return .targetItem(name: name)
       #else
-        return ._targetItem(name: name)
+        return ._targetItem(name: name, condition: nil)
       #endif
     }
 
@@ -617,36 +618,74 @@ extension Target.Dependency {
       #if PACKAGE_DESCRIPTION_4
         return .productItem(name: name, package: package)
       #else
-        return ._productItem(name: name, package: package)
+        return ._productItem(name: name, package: package, condition: nil)
       #endif
     }
 
-    /// Creates a dependency on a product from a package dependency.
+    /// Creates a by-name dependency that resolves to either a target or a product but
+    /// after the package graph has been loaded.
     ///
     /// - parameters:
-    ///   - name: The name of the product.
-    ///   - package: The name of the package.
-    @available(_PackageDescription, introduced: 5.2)
-    public static func product(name: String, package: String) -> Target.Dependency {
+    ///   - name: The name of the dependency, either a target or a product.
+    @available(_PackageDescription, obsoleted: 999)
+    public static func byName(name: String) -> Target.Dependency {
       #if PACKAGE_DESCRIPTION_4
-        return .productItem(name: name, package: package)
+        return .byNameItem(name: name)
       #else
-        return ._productItem(name: name, package: package)
+        return ._byNameItem(name: name, condition: nil)
       #endif
     }
 
+  #if !PACKAGE_DESCRIPTION_4
+    /// Creates a dependency on a product from a package dependency.
+    ///
+    /// - parameters:
+    ///   - name: The name of the product.
+    ///   - package: The name of the package.
+    @available(_PackageDescription, introduced: 5.2, obsoleted: 999)
+    public static func product(
+        name: String,
+        package: String
+    ) -> Target.Dependency {
+        return ._productItem(name: name, package: package, condition: nil)
+    }
+
+    /// Creates a dependency on a target in the same package.
+    ///
+    /// - parameters:
+    ///   - name: The name of the target.
+    ///   - condition: The condition under which the dependency is exercised.
+    @available(_PackageDescription, introduced: 999)
+    public static func target(name: String, condition: BuildSettingCondition? = nil) -> Target.Dependency {
+        return ._targetItem(name: name, condition: condition)
+    }
+
+    /// Creates a dependency on a product from a package dependency.
+    ///
+    /// - parameters:
+    ///   - name: The name of the product.
+    ///   - package: The name of the package.
+    ///   - condition: The condition under which the dependency is exercised.
+    @available(_PackageDescription, introduced: 999)
+    public static func product(
+        name: String,
+        package: String,
+        condition: BuildSettingCondition? = nil
+    ) -> Target.Dependency {
+        return ._productItem(name: name, package: package, condition: condition)
+    }
+
     /// Creates a by-name dependency that resolves to either a target or a product but
     /// after the package graph has been loaded.
     ///
     /// - parameters:
     ///   - name: The name of the dependency, either a target or a product.
-    public static func byName(name: String) -> Target.Dependency {
-      #if PACKAGE_DESCRIPTION_4
-        return .byNameItem(name: name)
-      #else
-        return ._byNameItem(name: name)
-      #endif
+    ///   - condition: The condition under which the dependency is exercised.
+    @available(_PackageDescription, introduced: 999)
+    public static func byName(name: String, condition: BuildSettingCondition? = nil) -> Target.Dependency {
+        return ._byNameItem(name: name, condition: condition)
     }
+  #endif
 }
 
 // MARK: ExpressibleByStringLiteral
@@ -661,7 +700,7 @@ extension Target.Dependency: ExpressibleByStringLiteral {
       #if PACKAGE_DESCRIPTION_4
         self = .byNameItem(name: value)
       #else
-        self = ._byNameItem(name: value)
+        self = ._byNameItem(name: value, condition: nil)
       #endif
     }
 }