Improve errors.

Partial #313

Signed-off-by: Ross Goldberg <484615+rgoldberg@users.noreply.github.com>

Sources/mas/Commands/Uninstall.swift

@@ -44,7 +44,7 @@ extension Mas {
                         try appLibrary.uninstallApp(app: installedApp)
                     }
                 } catch {
-                    throw MASError.uninstallFailed
+                    throw error as? MASError ?? MASError.uninstallFailed(error: error as NSError)
                 }
             }
         }

Sources/mas/Controllers/MasAppLibrary.swift

@@ -51,8 +51,7 @@ class MasAppLibrary: AppLibrary {
                 printInfo("App moved to trash: \(path)")
             }
         } catch {
-            printError("Unable to move app to trash.")
-            throw MASError.uninstallFailed
+            throw MASError.uninstallFailed(error: error as NSError)
         }
     }
 }

Sources/mas/Errors/MASError.swift

@@ -28,7 +28,7 @@ enum MASError: Error, Equatable {
     case noVendorWebsite
 
     case notInstalled(appID: AppID)
-    case uninstallFailed
+    case uninstallFailed(error: NSError?)
     case macOSUserMustBeRoot
 
     case noData
@@ -83,7 +83,10 @@ extension MASError: CustomStringConvertible {
             return "App does not have a vendor website"
         case .notInstalled(let appID):
             return "No apps installed with app ID \(appID)"
-        case .uninstallFailed:
+        case .uninstallFailed(let error):
+            if let error {
+                return "Uninstall failed: \(error.localizedDescription)"
+            }
             return "Uninstall failed"
         case .macOSUserMustBeRoot:
             return "Apps installed from the Mac App Store require root permission to remove."

Tests/masTests/Commands/UninstallSpec.swift

@@ -78,7 +78,7 @@ public class UninstallSpec: QuickSpec {
                     expect {
                         try uninstall.run(appLibrary: mockLibrary)
                     }
-                    .to(throwError(MASError.uninstallFailed))
+                    .to(throwError(MASError.uninstallFailed(error: nil)))
                 }
             }
         }

Tests/masTests/Controllers/AppLibraryMock.swift

@@ -20,7 +20,7 @@ class AppLibraryMock: AppLibrary {
 
         // Special case for testing where we pretend the trash command failed
         if app.bundlePath == "/dev/null" {
-            throw MASError.uninstallFailed
+            throw MASError.uninstallFailed(error: nil)
         }
 
         // Success is the default, watch out for false positives!

Tests/masTests/Errors/MASErrorTestCase.swift

@@ -114,7 +114,7 @@ class MASErrorTestCase: XCTestCase {
     }
 
     func testUninstallFailed() {
-        error = .uninstallFailed
+        error = .uninstallFailed(error: nil)
         XCTAssertEqual(error.description, "Uninstall failed")
     }