Make anyTranscodeFailure more descriptive

Right now it's quite difficult to identify _which type_ is missing from the `Google_Protobuf_Any` registry when the `anyTranscodeFailure` is thrown without having Xcode and breakpoints to debug the program. This change makes the error more descriptive and actionable by including the type URL that needs to be registered.

Sources/SwiftProtobuf/AnyMessageStorage.swift

@@ -210,7 +210,7 @@ internal class AnyMessageStorage {
     case .contentJSON(let contentJSON, let options):
       // contentJSON requires we have the type available for decoding
       guard let messageType = Google_Protobuf_Any.messageType(forTypeURL: _typeURL) else {
-          throw BinaryEncodingError.anyTranscodeFailure
+          throw BinaryEncodingError.anyTypeURLNotRegistered(typeURL: _typeURL)
       }
       do {
         // Decodes the full JSON and then discard the result.
@@ -414,7 +414,7 @@ extension AnyMessageStorage {
         // binary value, so we're stuck.  (The Google spec does not
         // provide a way to just package the binary value for someone
         // else to decode later.)
-        throw JSONEncodingError.anyTranscodeFailure
+        throw JSONEncodingError.anyTypeURLNotRegistered(typeURL: _typeURL)
       }
       let m = try messageType.init(serializedBytes: valueData, partial: true)
       return try serializeAnyJSON(for: m, typeURL: _typeURL, options: options)

Sources/SwiftProtobuf/BinaryEncodingError.swift

@@ -13,18 +13,18 @@
 // -----------------------------------------------------------------------------
 
 /// Describes errors that can occur when decoding a message from binary format.
-public enum BinaryEncodingError: Error {
+public enum BinaryEncodingError: Error, Equatable {
   /// `Any` fields that were decoded from JSON cannot be re-encoded to binary
   /// unless the object they hold is a well-known type or a type registered via
   /// `Google_Protobuf_Any.register()`.
+  case anyTypeURLNotRegistered(typeURL: String)
+  /// An unexpected failure when deserializing a `Google_Protobuf_Any`.
   case anyTranscodeFailure
-
   /// The definition of the message or one of its nested messages has required
   /// fields but the message being encoded did not include values for them. You
   /// must pass `partial: true` during encoding if you wish to explicitly ignore
   /// missing required fields.
   case missingRequiredFields
-
   /// Messages are limited to a maximum of 2GB in encoded size.
   case tooLarge
 }

Sources/SwiftProtobuf/JSONEncodingError.swift

@@ -12,12 +12,12 @@
 ///
 // -----------------------------------------------------------------------------
 
-public enum JSONEncodingError: Error {
+public enum JSONEncodingError: Error, Equatable {
     /// Any fields that were decoded from binary format cannot be
     /// re-encoded into JSON unless the object they hold is a
     /// well-known type or a type registered with via
     /// Google_Protobuf_Any.register()
-    case anyTranscodeFailure
+    case anyTypeURLNotRegistered(typeURL: String)
     /// Timestamp values can only be JSON encoded if they hold a value
     /// between 0001-01-01Z00:00:00 and 9999-12-31Z23:59:59.
     case timestampRange