Fix failure if package has no dependencies

Sources/SwiftDependencyUpdaterLibrary/Dependency.swift

@@ -31,6 +31,9 @@ struct Dependency {
 
     static func loadDependencies(from folder: URL) throws -> [Dependency] {
         let packageDescription = try PackageDescription.loadPackageDescription(from: folder)
+        if packageDescription.dependencies.isEmpty {
+            return []
+        }
         let resolvedPackage = try ResolvedPackage.loadResolvedPackage(from: folder)
         let swiftPackageUpdates = try SwiftPackageUpdate.checkUpdates(in: folder)
         return try mergeDependencies(packageDescription: packageDescription, resolvedPackage: resolvedPackage, swiftPackageUpdates: swiftPackageUpdates)

Sources/SwiftDependencyUpdaterLibrary/SwiftPackageUpdate.swift

@@ -36,7 +36,7 @@ struct SwiftPackageUpdate {
             return output
         } catch {
             let error = error as! ShellOutError // swiftlint:disable:this force_cast
-            throw PackageDescriptionError.loadingFailed(error.message)
+            throw SwiftPackageUpdateError.loadingFailed(error.message)
         }
     }
 

Tests/SwiftDependencyUpdaterLibraryTests/Extensions/XCTestCase.swift

@@ -47,6 +47,18 @@ extension XCTestCase {
         return folder
     }
 
+    func createEmptySwiftPackage() -> URL {
+        let folder = emptyFolderURL()
+        let packageSwift = temporaryFileURL(in: folder, name: "Package.swift")
+        createFile(at: packageSwift, content: TestUtils.emptyPackageSwiftFileContent)
+        let packageResolved = temporaryFileURL(in: folder, name: "Package.resolved")
+        createFile(at: packageResolved, content: TestUtils.emptyPackageResolvedFileContent)
+        let sourceFile = temporaryFileURL(in: folder.appendingPathComponent("Sources/Name"), name: "Name.swift")
+        createFile(at: sourceFile, content: "")
+
+        return folder
+    }
+
     func assert<T, E: Error & Equatable>(_ expression: @autoclosure () throws -> T, throws expectedError: E, in file: StaticString = #file, line: UInt = #line) {
         var caughtError: Error?
 

Tests/SwiftDependencyUpdaterLibraryTests/SubCommands/GitHubCommandTests.swift

@@ -116,7 +116,7 @@ class GitHubCommandTests: XCTestCase {
     func testInvalidPackage() {
         let folder = emptyFolderURL()
         let packageSwift = temporaryFileURL(in: folder, name: "Package.swift")
-        createFile(at: packageSwift, content: TestUtils.emptyPackageSwiftFileContent)
+        createFile(at: packageSwift, content: "// swift-tools-version:5.4")
         let packageResolved = temporaryFileURL(in: folder, name: "Package.resolved")
         createFile(at: packageResolved, content: TestUtils.emptyPackageResolvedFileContent)
         let result = outputFromExecutionWith(arguments: ["github", folder.path])
@@ -266,16 +266,4 @@ class GitHubCommandTests: XCTestCase {
             enforceOrder: true)
     }
 
-    func createEmptySwiftPackage() -> URL {
-        let folder = emptyFolderURL()
-        let packageSwift = temporaryFileURL(in: folder, name: "Package.swift")
-        createFile(at: packageSwift, content: TestUtils.emptyPackageSwiftFileContent)
-        let packageResolved = temporaryFileURL(in: folder, name: "Package.resolved")
-        createFile(at: packageResolved, content: TestUtils.emptyPackageResolvedFileContent)
-        let sourceFile = temporaryFileURL(in: folder.appendingPathComponent("Sources/Name"), name: "Name.swift")
-        createFile(at: sourceFile, content: "")
-
-        return folder
-    }
-
 }

Tests/SwiftDependencyUpdaterLibraryTests/SubCommands/ListCommandTests.swift

@@ -22,7 +22,7 @@ class ListCommandTests: XCTestCase {
     func testInvalidPackage() {
         let folder = emptyFolderURL()
         let packageSwift = temporaryFileURL(in: folder, name: "Package.swift")
-        createFile(at: packageSwift, content: TestUtils.emptyPackageSwiftFileContent)
+        createFile(at: packageSwift, content: "// swift-tools-version:5.4")
         let packageResolved = temporaryFileURL(in: folder, name: "Package.resolved")
         createFile(at: packageResolved, content: TestUtils.emptyPackageResolvedFileContent)
         let result = outputFromExecutionWith(arguments: ["list", folder.path])
@@ -55,16 +55,4 @@ class ListCommandTests: XCTestCase {
         XCTAssertEqual(result.output, "No dependencies found.")
     }
 
-    func createEmptySwiftPackage() -> URL {
-        let folder = emptyFolderURL()
-        let packageSwift = temporaryFileURL(in: folder, name: "Package.swift")
-        createFile(at: packageSwift, content: TestUtils.emptyPackageSwiftFileContent)
-        let packageResolved = temporaryFileURL(in: folder, name: "Package.resolved")
-        createFile(at: packageResolved, content: TestUtils.emptyPackageResolvedFileContent)
-        let sourceFile = temporaryFileURL(in: folder.appendingPathComponent("Sources/Name"), name: "Name.swift")
-        createFile(at: sourceFile, content: "")
-
-        return folder
-    }
-
 }

Tests/SwiftDependencyUpdaterLibraryTests/SubCommands/UpdateCommandTests.swift

@@ -22,7 +22,7 @@ class UpdateCommandTests: XCTestCase {
     func testInvalidPackage() {
         let folder = emptyFolderURL()
         let packageSwift = temporaryFileURL(in: folder, name: "Package.swift")
-        createFile(at: packageSwift, content: TestUtils.emptyPackageSwiftFileContent)
+        createFile(at: packageSwift, content: "// swift-tools-version:5.4")
         let packageResolved = temporaryFileURL(in: folder, name: "Package.resolved")
         createFile(at: packageResolved, content: TestUtils.emptyPackageResolvedFileContent)
         let result = outputFromExecutionWith(arguments: ["update", folder.path])
@@ -55,16 +55,4 @@ class UpdateCommandTests: XCTestCase {
         XCTAssertEqual(result.output, "Everything is already up-to-date!")
     }
 
-    func createEmptySwiftPackage() -> URL {
-        let folder = emptyFolderURL()
-        let packageSwift = temporaryFileURL(in: folder, name: "Package.swift")
-        createFile(at: packageSwift, content: TestUtils.emptyPackageSwiftFileContent)
-        let packageResolved = temporaryFileURL(in: folder, name: "Package.resolved")
-        createFile(at: packageResolved, content: TestUtils.emptyPackageResolvedFileContent)
-        let sourceFile = temporaryFileURL(in: folder.appendingPathComponent("Sources/Name"), name: "Name.swift")
-        createFile(at: sourceFile, content: "")
-
-        return folder
-    }
-
 }

Tests/SwiftDependencyUpdaterLibraryTests/SwiftPackageUpdateTests.swift

@@ -28,4 +28,17 @@ class SwiftPackageUpdateTests: XCTestCase {
         Rainbow.enabled = originalValue
     }
 
+    func testCheckUpdatesEmptyFolder() {
+        let folder = emptyFolderURL()
+        assert(
+            try SwiftPackageUpdate.checkUpdates(in: folder),
+            throws: SwiftPackageUpdateError.loadingFailed("error: root manifest not found")
+        )
+    }
+
+    func testCheckUpdatesEmptySwiftPackage() {
+        let folder = createEmptySwiftPackage()
+        XCTAssert(try! SwiftPackageUpdate.checkUpdates(in: folder).isEmpty)
+    }
+
 }