Add CustomChainedErrorDescriptionProtocol

1 files changed, 51 insertions, 18 deletions

diff --git a/ios/MullvadVPN/ChainedError.swift b/ios/MullvadVPN/ChainedError.swift
index 86977609a1..446ed99469 100644
--- a/ios/MullvadVPN/ChainedError.swift
+++ b/ios/MullvadVPN/ChainedError.swift
@@ -8,26 +8,19 @@
 
 import Foundation
 
-/// A protocol describing errors that can be chained together
+/// A protocol describing errors that can be chained together.
 protocol ChainedError: LocalizedError {
-    /// A source error when available
+    /// A source error when available.
     var source: Error? { get }
 }
 
-final class AnyChainedError: ChainedError {
-    private let wrappedError: Error
-
-    init(_ error: Error) {
-        wrappedError = error
-    }
-
-    var errorDescription: String? {
-        return wrappedError.localizedDescription
-    }
+/// A protocol providing error a way to override error description when printing error chain.
+protocol CustomChainedErrorDescriptionProtocol {
+    /// A custom error description that overrides `localizedDescription` when printing error chain.
+    var customErrorDescription: String? { get }
 }
 
 extension ChainedError {
-
     var source: Error? {
         let reflection = Mirror(reflecting: self)
 
@@ -42,14 +35,20 @@ extension ChainedError {
         return nil
     }
 
-    /// Creates a string representation of the entire error chain.
-    /// An extra `message` is added at the start of the chain when given
+    /// Create a string representation of the entire error chain.
+    /// An extra `message` is added at the start of the chain when given.
     func displayChain(message: String? = nil) -> String {
-        var s = message.map { "Error: \($0)\nCaused by: \(self.localizedDescription)" }
-            ?? "Error: \(self.localizedDescription)"
+        var s: String
+
+        let errorDescription = Self.getErrorDescription(self)
+        if let message = message {
+            s = "Error: \(message)\nCaused by: \(errorDescription)"
+        } else {
+            s = "Error: \(errorDescription)"
+        }
 
         for sourceError in makeChainIterator() {
-            s.append("\nCaused by: \(sourceError.localizedDescription)")
+            s.append("\nCaused by: \(Self.getErrorDescription(sourceError))")
         }
 
         return s
@@ -62,4 +61,38 @@ extension ChainedError {
             return current
         }
     }
+
+    private static func getErrorDescription(_ error: Error) -> String {
+        let anError = error as? CustomChainedErrorDescriptionProtocol
+
+        return anError?.customErrorDescription ?? error.localizedDescription
+    }
+}
+
+extension CustomChainedErrorDescriptionProtocol {
+    var customErrorDescription: String? {
+        return nil
+    }
+}
+
+/// A type-erasing container type for any `Error` that makes the wrapped error behave like
+/// `ChainedError`.
+final class AnyChainedError: ChainedError, CustomChainedErrorDescriptionProtocol {
+    private let wrappedError: Error
+
+    init(_ error: Error) {
+        wrappedError = error
+    }
+
+    var source: Error? {
+        return (wrappedError as? ChainedError)?.source
+    }
+
+    var errorDescription: String? {
+        return wrappedError.localizedDescription
+    }
+
+    var customErrorDescription: String? {
+        return (wrappedError as? CustomChainedErrorDescriptionProtocol)?.customErrorDescription
+    }
 }