[PackageGraph] Fix package name validation for product target dependencies

The package name validation was wrong for product target dependencies
(`.product(name: "<product>", package: "<package>")`) as we were looking
up the package using its identity instead of the name. This completely
breaks package loading in 5.2 if a package wants to use a product from
a dependency that doesn't match the package name of that dependency.

<rdar://problem/59744465>

Author: aciidgh

Sources/PackageGraph/PackageGraphLoader.swift

@@ -271,20 +271,26 @@ private func createResolvedPackages(
     })
 
     // Create a map of package builders keyed by the package identity.
-    let packageMap: [String: ResolvedPackageBuilder] = packageBuilders.spm_createDictionary({
-        // FIXME: This shouldn't be needed once <rdar://problem/33693433> is fixed.
+    let packageMapByIdentity: [String: ResolvedPackageBuilder] = packageBuilders.spm_createDictionary{
         let identity = PackageReference.computeIdentity(packageURL: $0.package.manifest.url)
         return (identity, $0)
-    })
+    }
+    let packageMapByName: [String: ResolvedPackageBuilder] = packageBuilders.spm_createDictionary{ ($0.package.name, $0) }
 
     // In the first pass, we wire some basic things.
     for packageBuilder in packageBuilders {
         let package = packageBuilder.package
 
         // Establish the manifest-declared package dependencies.
-        packageBuilder.dependencies = package.manifest.allRequiredDependencies.compactMap({ dependency in
+        packageBuilder.dependencies = package.manifest.allRequiredDependencies.compactMap { dependency in
+            // Use the package name to lookup the dependency. The package name will be present in packages with tools version >= 5.2.
+            if let dependencyName = dependency.explicitName, let resolvedPackage = packageMapByName[dependencyName] {
+                return resolvedPackage
+            }
+
+            // Otherwise, look it up by its identity.
             let url = config.mirroredURL(forURL: dependency.url)
-            let resolvedPackage = packageMap[PackageReference.computeIdentity(packageURL: url)]
+            let resolvedPackage = packageMapByIdentity[PackageReference.computeIdentity(packageURL: url)]
 
             // We check that the explicit package dependency name matches the package name.
             if let resolvedPackage = resolvedPackage,
@@ -300,7 +306,7 @@ private func createResolvedPackages(
             }
 
             return resolvedPackage
-        })
+        }
 
         // Create target builders for each target in the package.
         let targetBuilders = package.targets.map({ ResolvedTargetBuilder(target: $0, diagnostics: diagnostics) })
@@ -403,7 +409,7 @@ private func createResolvedPackages(
                 if let packageName = productRef.package {
                     // Find the declared package and check that it contains
                     // the product we found above.
-                    guard let dependencyPackage = packageMap[packageName.lowercased()], dependencyPackage.products.contains(product) else {
+                    guard let dependencyPackage = packageMapByName[packageName], dependencyPackage.products.contains(product) else {
                         let error = PackageGraphError.productDependencyIncorrectPackage(
                             name: productRef.name, package: packageName)
                         diagnostics.emit(error, location: diagnosticLocation())

Tests/PackageGraphTests/PackageGraphTests.swift

@@ -632,6 +632,45 @@ class PackageGraphTests: XCTestCase {
         }
     }
 
+    func testPackageNameValidationInProductTargetDependency() throws {
+        let fs = InMemoryFileSystem(emptyFiles:
+            "/Foo/Sources/Foo/foo.swift",
+            "/Bar/Sources/Bar/bar.swift"
+        )
+
+        let diagnostics = DiagnosticsEngine()
+        _ = loadPackageGraph(fs: fs, diagnostics: diagnostics,
+            manifests: [
+                Manifest.createManifest(
+                    name: "Foo",
+                    path: "/Foo",
+                    url: "/Foo",
+                    v: .v5_2,
+                    packageKind: .root,
+                    dependencies: [
+                        PackageDependencyDescription(name: "UnBar", url: "/Bar", requirement: .branch("master")),
+                    ],
+                    targets: [
+                        TargetDescription(name: "Foo", dependencies: [.product(name: "BarProduct", package: "UnBar")]),
+                    ]),
+                Manifest.createV4Manifest(
+                    name: "UnBar",
+                    path: "/Bar",
+                    url: "/Bar",
+                    packageKind: .remote,
+                    products: [
+                        ProductDescription(name: "BarProduct", targets: ["Bar"])
+                    ],
+                    targets: [
+                        TargetDescription(name: "Bar"),
+                    ]),
+            ]
+        )
+
+        // Expect no diagnostics.
+        DiagnosticsEngineTester(diagnostics) { _ in }
+    }
+
     func testUnusedDependency() throws {
         let fs = InMemoryFileSystem(emptyFiles:
             "/Foo/Sources/Foo/foo.swift",