[Traits] Integrate traits into module loading

Fixtures/Traits/Example/Package.swift

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+// swift-tools-version: 999.0.0
+
+@_spi(ExperimentalTraits) import PackageDescription
+
+let package = Package(
+    name: "TraitsExample",
+    traits: [
+        Trait(name: "Package1", isDefault: true),
+        Trait(name: "Package2", isDefault: true),
+        Trait(name: "Package3", isDefault: true),
+        Trait(name: "Package4", isDefault: true),
+        "Package5",
+        "Package7",
+        "Package9",
+        "Package10",
+        Trait(name: "BuildCondition1", isDefault: true),
+        "BuildCondition2",
+        "BuildCondition3",
+    ],
+    dependencies: [
+        .package(
+            path: "../Package1",
+            traits: ["Package1Trait1"]
+        ),
+        .package(
+            path: "../Package2",
+            traits: ["Package2Trait1"]
+        ),
+        .package(
+            path: "../Package3"
+        ),
+        .package(
+            path: "../Package4",
+            traits: []
+        ),
+        .package(
+            path: "../Package5",
+            traits: ["Package5Trait1"]
+        ),
+        .package(
+            path: "../Package7"
+        ),
+        .package(
+            path: "../Package9"
+        ),
+        .package(
+            path: "../Package10",
+            traits: ["Package10Trait2"]
+        ),
+    ],
+    targets: [
+        .executableTarget(
+            name: "Example",
+            dependencies: [
+                .product(
+                    name: "Package1Library1",
+                    package: "Package1",
+                    condition: .when(traits: ["Package1"])
+                ),
+                .product(
+                    name: "Package2Library1",
+                    package: "Package2",
+                    condition: .when(traits: ["Package2"])
+                ),
+                .product(
+                    name: "Package3Library1",
+                    package: "Package3",
+                    condition: .when(traits: ["Package3"])
+                ),
+                .product(
+                    name: "Package4Library1",
+                    package: "Package4",
+                    condition: .when(traits: ["Package4"])
+                ),
+                .product(
+                    name: "Package5Library1",
+                    package: "Package5",
+                    condition: .when(traits: ["Package5"])
+                ),
+                .product(
+                    name: "Package7Library1",
+                    package: "Package7",
+                    condition: .when(traits: ["Package7"])
+                ),
+                .product(
+                    name: "Package9Library1",
+                    package: "Package9",
+                    condition: .when(traits: ["Package9"])
+                ),
+                .product(
+                    name: "Package10Library1",
+                    package: "Package10",
+                    condition: .when(traits: ["Package10"])
+                ),
+            ],
+            swiftSettings: [
+                .define("DEFINE1", .when(traits: ["BuildCondition1"])),
+                .define("DEFINE2", .when(traits: ["BuildCondition2"])),
+                .define("DEFINE3", .when(traits: ["BuildCondition3"])),
+            ]
+        ),
+    ]
+)

Fixtures/Traits/Example/Sources/Example/Example.swift

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+#if Package1
+import Package1Library1
+#endif
+#if Package2
+import Package2Library1
+#endif
+#if Package3
+import Package3Library1
+#endif
+#if Package4
+import Package4Library1
+#endif
+#if Package5
+import Package5Library1
+#endif
+#if Package7
+import Package7Library1
+#endif
+#if Package9
+import Package9Library1
+#endif
+#if Package10
+import Package10Library1
+#endif
+
+@main
+struct Example {
+    static func main() {
+        #if Package1
+        Package1Library1.hello()
+        #endif
+        #if Package2
+        Package2Library1.hello()
+        #endif
+        #if Package3
+        Package3Library1.hello()
+        #endif
+        #if Package4
+        Package4Library1.hello()
+        #endif
+        #if Package5
+        Package5Library1.hello()
+        #endif
+        #if Package7
+        Package7Library1.hello()
+        #endif
+        #if Package9
+        Package9Library1.hello()
+        #endif
+        #if Package10
+        Package10Library1.hello()
+        #endif
+        #if DEFINE1
+        print("DEFINE1 enabled")
+        #else
+        print("DEFINE1 disabled")
+        #endif
+        #if DEFINE2
+        print("DEFINE2 enabled")
+        #else
+        print("DEFINE2 disabled")
+        #endif
+        #if DEFINE3
+        print("DEFINE3 enabled")
+        #else
+        print("DEFINE3 disabled")
+        #endif
+    }
+}

Fixtures/Traits/Package1/Package.swift

@@ -0,0 +1,21 @@
+// swift-tools-version: 999.0.0
+
+@_spi(ExperimentalTraits) import PackageDescription
+
+let package = Package(
+    name: "Package1",
+    products: [
+        .library(
+            name: "Package1Library1",
+            targets: ["Package1Library1"]
+        ),
+    ],
+    traits: [
+        "Package1Trait1"
+    ],
+    targets: [
+        .target(
+            name: "Package1Library1"
+        ),
+    ]
+)

Fixtures/Traits/Package1/Sources/Package1Library1/Library.swift

@@ -0,0 +1,7 @@
+public func hello() {
+    #if Package1Trait1
+    print("Package1Library1 trait1 enabled")
+    #else
+    print("Package1Library1 trait1 disabled")
+    #endif
+}

Fixtures/Traits/Package10/Package.swift

@@ -0,0 +1,22 @@
+// swift-tools-version: 999.0.0
+
+@_spi(ExperimentalTraits) import PackageDescription
+
+let package = Package(
+    name: "Package10",
+    products: [
+        .library(
+            name: "Package10Library1",
+            targets: ["Package10Library1"]
+        ),
+    ],
+    traits: [
+        "Package10Trait1",
+        "Package10Trait2"
+    ],
+    targets: [
+        .target(
+            name: "Package10Library1"
+        ),
+    ]
+)

Fixtures/Traits/Package10/Sources/Package10Library1/Library.swift

@@ -0,0 +1,12 @@
+public func hello() {
+    #if Package10Trait1
+    print("Package10Library1 trait1 enabled")
+    #else
+    print("Package10Library1 trait1 disabled")
+    #endif
+    #if Package10Trait2
+    print("Package10Library1 trait2 enabled")
+    #else
+    print("Package10Library1 trait2 disabled")
+    #endif
+}

Fixtures/Traits/Package2/Package.swift

@@ -0,0 +1,22 @@
+// swift-tools-version: 999.0.0
+
+@_spi(ExperimentalTraits) import PackageDescription
+
+let package = Package(
+    name: "Package2",
+    products: [
+        .library(
+            name: "Package2Library1",
+            targets: ["Package2Library1"]
+        ),
+    ],
+    traits: [
+        Trait(name: "Package2Trait1", enabledTraits: ["Package2Trait2"]),
+        "Package2Trait2",
+    ],
+    targets: [
+        .target(
+            name: "Package2Library1"
+        ),
+    ]
+)

Fixtures/Traits/Package2/Sources/Package2Library1/Library.swift

@@ -0,0 +1,7 @@
+public func hello() {
+    #if Package2Trait2
+    print("Package2Library1 trait2 enabled")
+    #else
+    print("Package2Library1 trait2 disabled")
+    #endif
+}

Fixtures/Traits/Package3/Package.swift

@@ -0,0 +1,23 @@
+// swift-tools-version: 999.0.0
+
+@_spi(ExperimentalTraits) import PackageDescription
+
+let package = Package(
+    name: "Package3",
+    products: [
+        .library(
+            name: "Package3Library1",
+            targets: ["Package3Library1"]
+        ),
+    ],
+    traits: [
+        Trait(name: "Package3Trait1", enabledTraits: ["Package3Trait2"]),
+        Trait(name: "Package3Trait2", enabledTraits: ["Package3Trait3"]),
+        Trait(name: "Package3Trait3", isDefault: true),
+    ],
+    targets: [
+        .target(
+            name: "Package3Library1"
+        ),
+    ]
+)

Fixtures/Traits/Package3/Sources/Package3Library1/Library.swift

@@ -0,0 +1,7 @@
+public func hello() {
+    #if Package3Trait3
+    print("Package3Library1 trait3 enabled")
+    #else
+    print("Package3Library1 trait3 disabled")
+    #endif
+}

Fixtures/Traits/Package4/Package.swift

@@ -0,0 +1,21 @@
+// swift-tools-version: 999.0.0
+
+@_spi(ExperimentalTraits) import PackageDescription
+
+let package = Package(
+    name: "Package4",
+    products: [
+        .library(
+            name: "Package4Library1",
+            targets: ["Package4Library1"]
+        ),
+    ],
+    traits: [
+        Trait(name: "Package4Trait1", isDefault: true),
+    ],
+    targets: [
+        .target(
+            name: "Package4Library1"
+        ),
+    ]
+)

Fixtures/Traits/Package4/Sources/Package4Library1/Library.swift

@@ -0,0 +1,7 @@
+public func hello() {
+    #if Package4Trait1
+    print("Package4Library1 trait1 enabled")
+    #else
+    print("Package4Library1 trait1 disabled")
+    #endif
+}

Fixtures/Traits/Package5/Package.swift

@@ -0,0 +1,35 @@
+// swift-tools-version: 999.0.0
+
+@_spi(ExperimentalTraits) import PackageDescription
+
+let package = Package(
+    name: "Package5",
+    products: [
+        .library(
+            name: "Package5Library1",
+            targets: ["Package5Library1"]
+        ),
+    ],
+    traits: [
+        "Package5Trait1"
+    ],
+    dependencies: [
+        .package(
+            path: "../Package6",
+            traits: [
+                Package.Dependency.Trait(name: "Package6Trait1", condition: .when(traits: ["Package5Trait1"]))
+            ]
+        )
+    ],
+    targets: [
+        .target(
+            name: "Package5Library1",
+            dependencies: [
+                .product(
+                    name: "Package6Library1",
+                    package: "Package6"
+                )
+            ]
+        ),
+    ]
+)

Fixtures/Traits/Package5/Sources/Package5Library1/Library.swift

@@ -0,0 +1,12 @@
+#if Package5Trait1
+import Package6Library1
+#endif
+
+public func hello() {
+    #if Package5Trait1
+    print("Package5Library1 trait1 enabled")
+    Package6Library1.hello()
+    #else
+    print("Package5Library1 trait1 disabled")
+    #endif
+}