SWIFT-1004 Support parsing $uuid as extended JSON representation for subtype 4 binary (#50)

Author: ncarbon

Sources/SwiftBSON/BSONBinary.swift

@@ -158,6 +158,32 @@ extension BSONBinary: BSONValue {
      *   - `DecodingError` if `json` is a partial match or is malformed.
      */
     internal init?(fromExtJSON json: JSON, keyPath: [String]) throws {
+        if let uuidJSON = try json.unwrapObject(withKey: "$uuid", keyPath: keyPath) {
+            guard let uuidString = uuidJSON.stringValue else {
+                throw DecodingError._extendedJSONError(
+                    keyPath: keyPath,
+                    debugDescription: "Expected value for key $uuid \"\(uuidJSON)\" to be a string"
+                        + " but got some other value"
+                )
+            }
+            guard let uuid = UUID(uuidString: uuidString) else {
+                throw DecodingError._extendedJSONError(
+                    keyPath: keyPath,
+                    debugDescription: "Invalid UUID string: \(uuidString)"
+                )
+            }
+
+            do {
+                self = try BSONBinary(from: uuid)
+                return
+            } catch {
+                throw DecodingError._extendedJSONError(
+                    keyPath: keyPath,
+                    debugDescription: error.localizedDescription
+                )
+            }
+        }
+
         // canonical and relaxed extended JSON
         guard let binary = try json.unwrapObject(withKey: "$binary", keyPath: keyPath) else {
             return nil

Tests/Specs/bson-corpus/binary.json

@@ -39,6 +39,12 @@
             "canonical_bson": "1D000000057800100000000473FFD26444B34C6990E8E7D1DFC035D400",
             "canonical_extjson": "{\"x\" : { \"$binary\" : {\"base64\" : \"c//SZESzTGmQ6OfR38A11A==\", \"subType\" : \"04\"}}}"
         },
+        {
+            "description": "subtype 0x04 UUID",
+            "canonical_bson": "1D000000057800100000000473FFD26444B34C6990E8E7D1DFC035D400",
+            "canonical_extjson": "{\"x\" : { \"$binary\" : {\"base64\" : \"c//SZESzTGmQ6OfR38A11A==\", \"subType\" : \"04\"}}}",
+            "degenerate_extjson": "{\"x\" : { \"$uuid\" : \"73ffd264-44b3-4c69-90e8-e7d1dfc035d4\"}}"
+        },
         {
             "description": "subtype 0x05",
             "canonical_bson": "1D000000057800100000000573FFD26444B34C6990E8E7D1DFC035D400",
@@ -81,5 +87,15 @@
             "description": "subtype 0x02 length negative one",
             "bson": "130000000578000600000002FFFFFFFFFFFF00"
         }
+    ],
+    "parseErrors": [
+        {
+            "description": "$uuid wrong type",
+            "string": "{\"x\" : { \"$uuid\" : { \"data\" : \"73ffd264-44b3-4c69-90e8-e7d1dfc035d4\"}}}"
+        },
+        {
+            "description": "$uuid invalid value",
+            "string": "{\"x\" : { \"$uuid\" : \"73ffd264-44b3-90e8-e7d1dfc035d4\"}}"
+        }
     ]
 }

Tests/SwiftBSONTests/BSONCorpusTests.swift

@@ -243,7 +243,7 @@ final class BSONCorpusTests: BSONTestCase {
                     }
                     let description = "\(testFile.description)-\(test.description)"
                     switch BSONType(rawValue: UInt8(testFile.bsonType.dropFirst(2), radix: 16)!)! {
-                    case .invalid: // "top level document" uses 0x00 for the bson type
+                    case .binary, .invalid: // "top level document" uses 0x00 for the bson type
                         guard let testData = test.string.data(using: .utf8) else {
                             XCTFail("Unable to interpret canonical_bson as Data")
                             return