Fixed crash when serializing an invalid dictionary

EosioSwift.xcodeproj/project.pbxproj

@@ -25,6 +25,7 @@
 		3EE762A22268C48D00D8DC33 /* EosioRpcProviderEndpointsPromises.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3EE762A12268C48D00D8DC33 /* EosioRpcProviderEndpointsPromises.swift */; };
 		3EE762A422690E9200D8DC33 /* RpcProviderEndpointPromiseTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3EE762A322690E9200D8DC33 /* RpcProviderEndpointPromiseTests.swift */; };
 		4FD31C65A4889CF91BFCE984 /* Pods_EosioSwift.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D3E4478EE834B70DDF06A7FA /* Pods_EosioSwift.framework */; };
+		5D8C430D235F986700F3A146 /* DictionaryExtensionTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5D8C430C235F986700F3A146 /* DictionaryExtensionTests.swift */; };
 		6B80D26921FA6DDF00716A7B /* EosioSwift.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 6B80D25F21FA6DDF00716A7B /* EosioSwift.framework */; };
 		6B80D27021FA6DDF00716A7B /* EosioSwift.h in Headers */ = {isa = PBXBuildFile; fileRef = 6B80D26221FA6DDF00716A7B /* EosioSwift.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		8F49E8CF225E6E6A00082631 /* RpcProviderRequestModels.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8F49E8CE225E6E6A00082631 /* RpcProviderRequestModels.swift */; };
@@ -99,6 +100,7 @@
 		3EE762A322690E9200D8DC33 /* RpcProviderEndpointPromiseTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = RpcProviderEndpointPromiseTests.swift; sourceTree = "<group>"; };
 		5835070C5F7998E17BF06017 /* Pods_EosioSwiftTests.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Pods_EosioSwiftTests.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		5ACC322368A39C81F88A1553 /* Pods-EosioSwift.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-EosioSwift.debug.xcconfig"; path = "Pods/Target Support Files/Pods-EosioSwift/Pods-EosioSwift.debug.xcconfig"; sourceTree = "<group>"; };
+		5D8C430C235F986700F3A146 /* DictionaryExtensionTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DictionaryExtensionTests.swift; sourceTree = "<group>"; };
 		6B80D25F21FA6DDF00716A7B /* EosioSwift.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = EosioSwift.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		6B80D26221FA6DDF00716A7B /* EosioSwift.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = EosioSwift.h; sourceTree = "<group>"; };
 		6B80D26321FA6DDF00716A7B /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
@@ -258,6 +260,7 @@
 			isa = PBXGroup;
 			children = (
 				8F6B04CA22287B1D00215CD0 /* DataExtensionsTests.swift */,
+				5D8C430C235F986700F3A146 /* DictionaryExtensionTests.swift */,
 				8F6B04C722287B1D00215CD0 /* EncodableExtensionTests.swift */,
 				8F6B04CB22287B1D00215CD0 /* EosioNameTests.swift */,
 				8F6B04C922287B1D00215CD0 /* StringExtensionsTests.swift */,
@@ -617,6 +620,7 @@
 				8F6B04CE22287B1D00215CD0 /* StringExtensionsTests.swift in Sources */,
 				BBAC7BCE225266A40035CDBC /* DateExtensionTests.swift in Sources */,
 				8F77127D2232FD6D004256D3 /* EosioTransactionTests.swift in Sources */,
+				5D8C430D235F986700F3A146 /* DictionaryExtensionTests.swift in Sources */,
 				1F9DCB7A22569A2600853105 /* EosioRpcProviderTests.swift in Sources */,
 				B4E8F6C222320EB700FA7E63 /* RIPEMD160Tests.swift in Sources */,
 				8F6B04CF22287B1D00215CD0 /* DataExtensionsTests.swift in Sources */,

EosioSwift/Extensions/DictionaryExtensions.swift

@@ -12,7 +12,8 @@ public extension Dictionary {
 
     /// Returns a JSON string representation of the dictionary or nil if the dictionary can't be encoded to a JSON string.
     var jsonString: String? {
-        guard let jsonData = try? JSONSerialization.data(withJSONObject: self, options: [.sortedKeys]) else { return nil }
+        guard JSONSerialization.isValidJSONObject(self),
+            let jsonData = try? JSONSerialization.data(withJSONObject: self, options: [.sortedKeys]) else { return nil }
         return String(data: jsonData, encoding: .utf8)
     }
 

EosioSwiftTests/DictionaryExtensionTests.swift

@@ -0,0 +1,39 @@
+//
+//  DictionaryExtensionTests.swift
+//  EosioSwiftTests
+
+//  Created by Paul Kim on 10/22/19
+//  Copyright (c) 2017-2019 block.one and its contributors. All rights reserved.
+//
+
+import XCTest
+
+class DictionaryExtensionTests: XCTestCase {
+
+    func testJsonStringWithValidDictionaryReturnsCorrectJsonString() {
+        let dict: [String: Any?] = ["string": "string",
+                                   "integer": 1,
+                                   "nil": nil,
+                                   "array": ["a", "b", "c"],
+                                   "dict": ["key": "value"]]
+        let expectedJsonString = "{\"array\":[\"a\",\"b\",\"c\"],\"dict\":{\"key\":\"value\"},\"integer\":1,\"nil\":null,\"string\":\"string\"}"
+
+        guard let resultingJsonString = dict.jsonString else {
+            return XCTFail("jsonString on valid dictionary returns nil.")
+        }
+        XCTAssertEqual(resultingJsonString, expectedJsonString)
+    }
+
+    func testJsonStringWithInvalidDictionaryReturnsNil() {
+        let dict: [String: Any?] = ["string": "string",
+                                   "integer": 1,
+                                   "nil": nil,
+                                   "array": ["a", "b", "c"],
+                                   "dict": ["key": "value"],
+                                   "enum": Calendar.Identifier.gregorian]
+
+        let resultingJsonString = dict.jsonString
+        XCTAssertNil(resultingJsonString, "jsonString on invalid dictionary returns non-nil.")
+    }
+
+}