[AltServer] Improves ALTServerErrorIncompatibleDeveloperDisk error message

Uses NSError’s debug description, if available, to populate error alerts.

Shared/Categories/NSError+ALTServerError.m

@@ -33,6 +33,10 @@ NSErrorUserInfoKey const ALTOperatingSystemVersionErrorKey = @"ALTOperatingSyste
         {
             return [error altserver_localizedRecoverySuggestion];
         }
+        else if ([userInfoKey isEqualToString:NSDebugDescriptionErrorKey])
+        {
+            return [error altserver_localizedDebugDescription];
+        }
         
         return nil;
     }];
@@ -172,6 +176,28 @@ NSErrorUserInfoKey const ALTOperatingSystemVersionErrorKey = @"ALTOperatingSyste
     }
 }
 
+- (nullable NSString *)altserver_localizedDebugDescription
+{
+    switch ((ALTServerError)self.code)
+    {
+        case ALTServerErrorIncompatibleDeveloperDisk:
+        {
+            NSString *path = self.userInfo[NSFilePathErrorKey];
+            if (path == nil)
+            {
+                return nil;
+            }
+
+            NSString *osVersion = [self altserver_osVersion] ?: NSLocalizedString(@"this device's OS version", @"");
+            NSString *debugDescription = [NSString stringWithFormat:NSLocalizedString(@"The Developer disk located at\n\n%@\n\nis incompatible with %@.", @""), path, osVersion];
+            return debugDescription;
+        }
+            
+        default:
+            return nil;
+    }
+}
+
 - (NSString *)profileErrorLocalizedDescriptionWithBaseDescription:(NSString *)baseDescription
 {
     NSString *localizedDescription = nil;

Shared/Extensions/NSError+AltStore.swift

@@ -16,6 +16,12 @@ extension NSError
         return localizedFailure
     }
     
+    @objc(alt_localizedDebugDescription)
+    var localizedDebugDescription: String? {
+        let debugDescription = (self.userInfo[NSDebugDescriptionErrorKey] as? String) ?? (NSError.userInfoValueProvider(forDomain: self.domain)?(self, NSDebugDescriptionErrorKey) as? String)
+        return debugDescription
+    }
+    
     @objc(alt_errorWithLocalizedFailure:)
     func withLocalizedFailure(_ failure: String) -> NSError
     {