From 6e4feecff0a1b951dc0b53b17c251b2e7d00cee5 Mon Sep 17 00:00:00 2001
From: Riley Testut <riley@rileytestut.com>
Date: Fri, 26 Feb 2021 13:50:50 -0600
Subject: [PATCH] Adds ALTLocalizedError.underlyingError

Allows for easily wrapping underlying errors while preserving localized descriptions.
---
 AltStore/Components/ToastView.swift        |  4 +--
 AltStore/Extensions/NSError+AltStore.swift | 38 ++++++++++++++++++++--
 2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/AltStore/Components/ToastView.swift b/AltStore/Components/ToastView.swift
index ec6ecdb5..b58c5dfa 100644
--- a/AltStore/Components/ToastView.swift
+++ b/AltStore/Components/ToastView.swift
@@ -49,7 +49,7 @@ class ToastView: RSTToastView
     convenience init(error: Error)
     {
         var error = error as NSError
-        var underlyingError = error.userInfo[NSUnderlyingErrorKey] as? NSError
+        var underlyingError = error.underlyingError
         
         var preferredDuration: TimeInterval?
         
@@ -59,7 +59,7 @@ class ToastView: RSTToastView
         {
             // Treat underlyingError as the primary error.
             
-            error = unwrappedUnderlyingError
+            error = unwrappedUnderlyingError as NSError
             underlyingError = nil
             
             preferredDuration = .longToastViewDuration
diff --git a/AltStore/Extensions/NSError+AltStore.swift b/AltStore/Extensions/NSError+AltStore.swift
index ccb01b7e..90b9346d 100644
--- a/AltStore/Extensions/NSError+AltStore.swift
+++ b/AltStore/Extensions/NSError+AltStore.swift
@@ -44,17 +44,49 @@ extension NSError
     }
 }
 
+extension Error
+{
+    var underlyingError: Error? {
+        let underlyingError = (self as NSError).userInfo[NSUnderlyingErrorKey] as? Error
+        return underlyingError
+    }
+}
+
 protocol ALTLocalizedError: LocalizedError, CustomNSError
 {
     var failure: String? { get }
+    
+    var underlyingError: Error? { get }
 }
 
 extension ALTLocalizedError
 {
     var errorUserInfo: [String : Any] {
-        let userInfo = [NSLocalizedDescriptionKey: self.errorDescription,
-                        NSLocalizedFailureReasonErrorKey: self.failureReason,
-                        NSLocalizedFailureErrorKey: self.failure].compactMapValues { $0 }
+        let userInfo = ([
+            NSLocalizedDescriptionKey: self.errorDescription,
+            NSLocalizedFailureReasonErrorKey: self.failureReason,
+            NSLocalizedFailureErrorKey: self.failure,
+            NSUnderlyingErrorKey: self.underlyingError
+        ] as [String: Any?]).compactMapValues { $0 }
         return userInfo
     }
+    
+    var underlyingError: Error? {
+        // Error's default implementation calls errorUserInfo,
+        // but ALTLocalizedError.errorUserInfo calls underlyingError.
+        // Return nil to prevent infinite recursion.
+        return nil
+    }
+    
+    var errorDescription: String? {
+        guard let errorFailure = self.failure else { return (self.underlyingError as NSError?)?.localizedDescription }
+        guard let failureReason = self.failureReason else { return errorFailure }
+        
+        let errorDescription = errorFailure + " " + failureReason
+        return errorDescription
+    }
+    
+    var failureReason: String? { (self.underlyingError as NSError?)?.localizedFailureReason ?? (self.underlyingError as NSError?)?.localizedDescription }
+    var recoverySuggestion: String? { (self.underlyingError as NSError?)?.localizedRecoverySuggestion }
+    var helpAnchor: String? { (self.underlyingError as NSError?)?.helpAnchor }
 }