Fix coding error bridging to NSError

CustomNSError briding only works when the CustomNSError conformance is in the same module as the original error declaration. We need to sink these down into the standard library.

Author: Itai Ferber

stdlib/public/SDK/Foundation/Codable.swift

@@ -14,59 +14,9 @@
 // Errors
 //===----------------------------------------------------------------------===//
 
-// Adding the following extensions to EncodingError and DecodingError allows them to bridge to NSErrors implicitly.
-
-fileprivate let NSCodingPathErrorKey = "NSCodingPath"
-fileprivate let NSDebugDescriptionErrorKey = "NSDebugDescription"
-
-extension EncodingError : CustomNSError {
-    public static var errorDomain: String = NSCocoaErrorDomain
-
-    public var errorCode: Int {
-        switch self {
-        case .invalidValue(_, _): return CocoaError.coderInvalidValue.rawValue
-        }
-    }
-
-    public var errorUserInfo: [String : Any] {
-        let context: Context
-        switch self {
-        case .invalidValue(_, let c): context = c
-        }
-
-        return [NSCodingPathErrorKey: context.codingPath,
-                NSDebugDescriptionErrorKey: context.debugDescription]
-    }
-}
-
-extension DecodingError : CustomNSError {
-    public static var errorDomain: String = NSCocoaErrorDomain
-
-    public var errorCode: Int {
-        switch self {
-        case .valueNotFound(_, _): fallthrough
-        case .keyNotFound(_, _):
-            return CocoaError._coderValueNotFound.rawValue
-
-        case .typeMismatch(_, _): fallthrough
-        case .dataCorrupted(_):
-            return CocoaError._coderReadCorrupt.rawValue
-        }
-    }
-
-    public var errorUserInfo: [String : Any]? {
-        let context: Context
-        switch self {
-        case .typeMismatch(_, let c): context = c
-        case .valueNotFound(_, let c): context = c
-        case .keyNotFound(_, let c): context = c
-        case .dataCorrupted(let c): context = c
-        }
-
-        return [NSCodingPathErrorKey: context.codingPath,
-                NSDebugDescriptionErrorKey: context.debugDescription]
-    }
-}
+// Both of these error types bridge to NSError, and through the entry points they use, no further work is needed to make them localized.
+extension EncodingError : LocalizedError {}
+extension DecodingError : LocalizedError {}
 
 //===----------------------------------------------------------------------===//
 // Error Utilities

stdlib/public/SDK/Foundation/NSError.swift

@@ -850,19 +850,11 @@ extension CocoaError.Code {
 
   @available(OSX, introduced: 10.11) @available(iOS, introduced: 9.0)
   public static var coderReadCorrupt: CocoaError.Code {
-    return _coderReadCorrupt
-  }
-
-  internal static var _coderReadCorrupt: CocoaError.Code {
     return CocoaError.Code(rawValue: 4864)
   }
 
   @available(OSX, introduced: 10.11) @available(iOS, introduced: 9.0)
   public static var coderValueNotFound: CocoaError.Code {
-    return _coderValueNotFound
-  }
-
-  internal static var _coderValueNotFound: CocoaError.Code {
     return CocoaError.Code(rawValue: 4865)
   }
 
@@ -1301,19 +1293,11 @@ extension CocoaError {
 
   @available(OSX, introduced: 10.11) @available(iOS, introduced: 9.0)
   public static var coderReadCorrupt: CocoaError.Code {
-    return _coderReadCorrupt
-  }
-
-  public static var _coderReadCorrupt: CocoaError.Code {
     return CocoaError.Code(rawValue: 4864)
   }
 
   @available(OSX, introduced: 10.11) @available(iOS, introduced: 9.0)
   public static var coderValueNotFound: CocoaError.Code {
-    return _coderValueNotFound
-  }
-
-  internal static var _coderValueNotFound: CocoaError.Code {
     return CocoaError.Code(rawValue: 4865)
   }
 

stdlib/public/core/Codable.swift

@@ -2045,6 +2045,44 @@ public enum EncodingError : Error {
     ///
     /// Contains the attempted value, along with context for debugging.
     case invalidValue(Any, Context)
+
+    // MARK: - NSError Bridging
+
+    // CustomNSError bridging applies only when the CustomNSError conformance is applied in the same module as the declared error type.
+    // Since we cannot access CustomNSError (which is defined in Foundation) from here, we can use the "hidden" entry points.
+
+    public var _domain: String {
+        return "NSCocoaErrorDomain"
+    }
+
+    public var _code: Int {
+        switch self {
+        case .invalidValue(_, _): return 4866
+        }
+    }
+
+    public var _userInfo: AnyObject? {
+        // The error dictionary must be returned as an AnyObject. We can do this only on platforms with bridging, unfortunately.
+        #if os(OSX) || os(iOS) || os(watchOS) || os(tvOS)
+            let context: Context
+            switch self {
+            case .invalidValue(_, let c): context = c
+            }
+
+            var userInfo: [String : Any] = [
+                "NSCodingPath": context.codingPath,
+                "NSDebugDescription": context.debugDescription
+            ]
+
+            if let underlyingError = context.underlyingError {
+                userInfo["NSUnderlyingError"] = underlyingError
+            }
+
+            return userInfo as AnyObject
+        #else
+            return nil
+        #endif
+    }
 }
 
 /// An error that occurs during the decoding of a value.
@@ -2091,6 +2129,50 @@ public enum DecodingError : Error {
     ///
     /// Contains context for debugging.
     case dataCorrupted(Context)
+
+    // MARK: - NSError Bridging
+
+    // CustomNSError bridging applies only when the CustomNSError conformance is applied in the same module as the declared error type.
+    // Since we cannot access CustomNSError (which is defined in Foundation) from here, we can use the "hidden" entry points.
+
+    public var _domain: String {
+        return "NSCocoaErrorDomain"
+    }
+
+    public var _code: Int {
+        switch self {
+        case .keyNotFound(_, _):   fallthrough
+        case .valueNotFound(_, _): return 4865
+        case .typeMismatch(_, _):  fallthrough
+        case .dataCorrupted(_):    return 4864
+        }
+    }
+
+    public var _userInfo: AnyObject? {
+        // The error dictionary must be returned as an AnyObject. We can do this only on platforms with bridging, unfortunately.
+        #if os(OSX) || os(iOS) || os(watchOS) || os(tvOS)
+            let context: Context
+            switch self {
+            case .keyNotFound(_,   let c): context = c
+            case .valueNotFound(_, let c): context = c
+            case .typeMismatch(_,  let c): context = c
+            case .dataCorrupted(   let c): context = c
+            }
+
+            var userInfo: [String : Any] = [
+                "NSCodingPath": context.codingPath,
+                "NSDebugDescription": context.debugDescription
+            ]
+
+            if let underlyingError = context.underlyingError {
+                userInfo["NSUnderlyingError"] = underlyingError
+            }
+
+            return userInfo as AnyObject
+        #else
+            return nil
+        #endif
+    }
 }
 
 //===----------------------------------------------------------------------===//