Resolve dependencies at the beginning

Sources/SwiftDependencyUpdaterLibrary/ResolvedPackage.swift

@@ -1,5 +1,6 @@
 import Foundation
 import Releases
+import ShellOut
 
 struct ResolvedVersion: Decodable {
 
@@ -50,6 +51,7 @@ private struct Wrapper: Decodable {
 }
 
 enum ResolvedPackageError: Error, Equatable {
+    case resolvingFailed(String)
     case readingFailed(String)
     case parsingFailed(String, String)
 }
@@ -62,6 +64,12 @@ struct ResolvedPackage: Decodable {
     let dependencies: [ResolvedDependency]
 
     static func loadResolvedPackage(from folder: URL) throws -> ResolvedPackage {
+         do {
+            try shellOut(to: "swift", arguments: ["package", "resolve", "--package-path", "\"\(folder.path)\"" ])
+        } catch {
+            let error = error as! ShellOutError // swiftlint:disable:this force_cast
+            throw ResolvedPackageError.resolvingFailed(error.message)
+        }
         let data = try readResolvedPackageData(from: folder)
         let decoder = JSONDecoder()
         do {
@@ -86,6 +94,8 @@ struct ResolvedPackage: Decodable {
 extension ResolvedPackageError: LocalizedError {
     public var errorDescription: String? {
         switch self {
+        case let .resolvingFailed(error):
+            return "Running swift package resolved failed: \(error)"
         case let .readingFailed(error):
             return "Could not read Package.resolved file: \(error)"
         case let .parsingFailed(error, packageData):

Tests/SwiftDependencyUpdaterLibraryTests/ResolvedPackageTests.swift

@@ -6,40 +6,30 @@ class ResolvedPackageTests: XCTestCase {
 
     func testEmptyFolder() {
         let folder = emptyFolderURL()
-        #if os(Linux)
         assert(
             try ResolvedPackage.loadResolvedPackage(from: folder),
-            throws: ResolvedPackageError.readingFailed("The operation could not be completed. No such file or directory")
+            throws: ResolvedPackageError.resolvingFailed("error: root manifest not found")
         )
-        #else
-        assert(
-            try ResolvedPackage.loadResolvedPackage(from: folder),
-            throws: ResolvedPackageError.readingFailed("The file “Package.resolved” couldn’t be opened because there is no such file.")
-        )
-        #endif
     }
 
     func testInvalidFile() {
         let folder = emptyFolderURL()
-        let file = temporaryFileURL(in: folder, name: "Package.resolved")
-        createFile(at: file, content: "\n")
-        #if os(Linux)
-        assert(
-            try ResolvedPackage.loadResolvedPackage(from: folder),
-            throws: ResolvedPackageError.parsingFailed("The operation could not be completed. The data isn’t in the correct format.", "\n")
-        )
-        #else
+        let resolvedFile = temporaryFileURL(in: folder, name: "Package.resolved")
+        createFile(at: resolvedFile, content: "\n")
+        let packageFile = temporaryFileURL(in: folder, name: "Package.swift")
+        createFile(at: packageFile, content: TestUtils.emptyPackageSwiftFileContent)
         assert(
             try ResolvedPackage.loadResolvedPackage(from: folder),
-            throws: ResolvedPackageError.parsingFailed("The data couldn’t be read because it isn’t in the correct format.", "\n")
+            throws: ResolvedPackageError.resolvingFailed("error: Package.resolved file is corrupted or malformed; fix or delete the file to continue: malformed")
         )
-        #endif
     }
 
     func testParsing() {
         let folder = emptyFolderURL()
-        let file = temporaryFileURL(in: folder, name: "Package.resolved")
-        createFile(at: file, content: TestUtils.packageResolvedFileContent)
+        let resolvedFile = temporaryFileURL(in: folder, name: "Package.resolved")
+        createFile(at: resolvedFile, content: TestUtils.packageResolvedFileContent)
+        let packageFile = temporaryFileURL(in: folder, name: "Package.swift")
+        createFile(at: packageFile, content: TestUtils.emptyPackageSwiftFileContent)
         let result = try! ResolvedPackage.loadResolvedPackage(from: folder)
         XCTAssertEqual(result.dependencies.count, 3)
 
@@ -95,6 +85,7 @@ class ResolvedPackageTests: XCTestCase {
     }
 
     func testResolvedPackageErrorString() {
+        XCTAssertEqual("\(ResolvedPackageError.resolvingFailed("abc").localizedDescription)", "Running swift package resolved failed: abc")
         XCTAssertEqual("\(ResolvedPackageError.readingFailed("abc").localizedDescription)", "Could not read Package.resolved file: abc")
         XCTAssertEqual("\(ResolvedPackageError.parsingFailed("abc", "def").localizedDescription)", "Could not parse package data: abc\n\nPackage Data: def")
     }