Refine error message with package name suggestion

Sources/PackageGraph/PackageGraph+Loading.swift

@@ -16,6 +16,7 @@ import PackageLoading
 import PackageModel
 
 import func TSCBasic.topologicalSort
+import func TSCBasic.bestMatch
 
 extension PackageGraph {
 
@@ -495,13 +496,16 @@ private func createResolvedPackages(
                         }.map {$0.targets}.flatMap{$0}.filter { t in
                             t.name != productRef.name
                         }
-
+
+                        // Find a product name from the available product dependencies that is most similar to the required product name.
+                        let bestMatchedProductName = bestMatch(for: productRef.name, from: Array(allTargetNames))
                         let error = PackageGraphError.productDependencyNotFound(
                             package: package.identity.description,
                             targetName: targetBuilder.target.name,
                             dependencyProductName: productRef.name,
                             dependencyPackageName: productRef.package,
-                            dependencyProductInDecl: !declProductsAsDependency.isEmpty
+                            dependencyProductInDecl: !declProductsAsDependency.isEmpty,
+                            similarProductName: bestMatchedProductName
                         )
                         packageObservabilityScope.emit(error)
                     }

Sources/PackageGraph/PackageGraph.swift

@@ -23,7 +23,7 @@ enum PackageGraphError: Swift.Error {
     case cycleDetected((path: [Manifest], cycle: [Manifest]))
 
     /// The product dependency not found.
-    case productDependencyNotFound(package: String, targetName: String, dependencyProductName: String, dependencyPackageName: String?, dependencyProductInDecl: Bool)
+    case productDependencyNotFound(package: String, targetName: String, dependencyProductName: String, dependencyPackageName: String?, dependencyProductInDecl: Bool, similarProductName: String?)
 
     /// The package dependency already satisfied by a different dependency package
     case dependencyAlreadySatisfiedByIdentifier(package: String, dependencyLocation: String, otherDependencyURL: String, identity: PackageIdentity)
@@ -219,11 +219,15 @@ extension PackageGraphError: CustomStringConvertible {
             (cycle.path + cycle.cycle).map({ $0.displayName }).joined(separator: " -> ") +
             " -> " + cycle.cycle[0].displayName
 
-        case .productDependencyNotFound(let package, let targetName, let dependencyProductName, let dependencyPackageName, let dependencyProductInDecl):
+        case .productDependencyNotFound(let package, let targetName, let dependencyProductName, let dependencyPackageName, let dependencyProductInDecl, let similarProductName):
             if dependencyProductInDecl {
                 return "product '\(dependencyProductName)' is declared in the same package '\(package)' and can't be used as a dependency for target '\(targetName)'."
             } else {
-                return "product '\(dependencyProductName)' required by package '\(package)' target '\(targetName)' \(dependencyPackageName.map{ "not found in package '\($0)'" } ?? "not found")."
+                var description = "product '\(dependencyProductName)' required by package '\(package)' target '\(targetName)' \(dependencyPackageName.map{ "not found in package '\($0)'" } ?? "not found")."
+                if let similarProductName {
+                    description += " Did you mean '\(similarProductName)'?"
+                }
+                return description
             }
         case .dependencyAlreadySatisfiedByIdentifier(let package, let dependencyURL, let otherDependencyURL, let identity):
             return "'\(package)' dependency on '\(dependencyURL)' conflicts with dependency on '\(otherDependencyURL)' which has the same identity '\(identity)'"

Tests/PackageGraphTests/PackageGraphTests.swift

@@ -786,6 +786,74 @@ class PackageGraphTests: XCTestCase {
         }
     }
 
+    func testProductDependencyWithSimilarName() throws {
+        let fs = InMemoryFileSystem(emptyFiles:
+            "/Foo/Sources/Foo/foo.swift",
+            "/Bar/Sources/Bar/bar.swift"
+        )
+
+        let observability = ObservabilitySystem.makeForTesting()
+        _ = try loadPackageGraph(
+            fileSystem: fs,
+            manifests: [
+                Manifest.createRootManifest(
+                    displayName: "Foo",
+                    path: "/Foo",
+                    targets: [
+                        TargetDescription(name: "Foo", dependencies: ["Barx"]),
+                    ]),
+                Manifest.createRootManifest(
+                    displayName: "Bar",
+                    path: "/Bar",
+                    targets: [
+                        TargetDescription(name: "Bar")
+                    ]),
+            ],
+            observabilityScope: observability.topScope
+        )
+
+        testDiagnostics(observability.diagnostics) { result in
+            result.check(
+                diagnostic: "product 'Barx' required by package 'foo' target 'Foo' not found. Did you mean 'Bar'?",
+                severity: .error
+            )
+        }
+    }
+
+    func testProductDependencyWithNonSimilarName() throws {
+        let fs = InMemoryFileSystem(emptyFiles:
+            "/Foo/Sources/Foo/foo.swift",
+            "/Bar/Sources/Bar/bar.swift"
+        )
+
+        let observability = ObservabilitySystem.makeForTesting()
+        _ = try loadPackageGraph(
+            fileSystem: fs,
+            manifests: [
+                Manifest.createRootManifest(
+                    displayName: "Foo",
+                    path: "/Foo",
+                    targets: [
+                        TargetDescription(name: "Foo", dependencies: ["Qux"]),
+                    ]),
+                Manifest.createRootManifest(
+                    displayName: "Bar",
+                    path: "/Bar",
+                    targets: [
+                        TargetDescription(name: "Bar")
+                    ]),
+            ],
+            observabilityScope: observability.topScope
+        )
+
+        testDiagnostics(observability.diagnostics) { result in
+            result.check(
+                diagnostic: "product 'Qux' required by package 'foo' target 'Foo' not found.",
+                severity: .error
+            )
+        }
+    }
+
     func testProductDependencyDeclaredInSamePackage() throws {
         let fs = InMemoryFileSystem(emptyFiles:
             "/Foo/Sources/FooTarget/src.swift",