Make it work on Linux (#5)

* Make Combine optional.

ProtocolTransportTests.testSendNotification(Async) are failing, as
the response has differently sorted keys in the JSON object

testDecodeFloatOverflow, testDecodeNotDouble and testDecodeOverflow
are failing due to different error messages for invalid input.
These messages are functionally the same

* Fix tests on Linux.

Author: JCWasmx86

Sources/JSONRPC/JSONValueDecoder.swift

@@ -1,5 +1,16 @@
 import Foundation
-import Combine
+#if canImport(Combine)
+    import Combine
+#else
+    public protocol TopLevelDecoder {
+        associatedtype Input
+
+        func decode<T>(
+            _ type: T.Type,
+            from: JSONValueDecoder.Input
+        ) throws -> T where T: Decodable
+    }
+#endif
 
 /// An object that decodes instances of a data type from `JSONValue` objects.
 public class JSONValueDecoder: TopLevelDecoder {

Tests/JSONRPCTests/JSONValueDecoderTests.swift

@@ -108,10 +108,17 @@ final class JSONValueDecoderTests: XCTestCase {
                 from: JSONValue.hash(["double": "string"])
             )
         ) { error in
-            XCTAssertEqual(
-                error.localizedDescription,
-                "The data couldn’t be read because it isn’t in the correct format."
-            )
+        	#if os(Linux)
+                        XCTAssertEqual(
+		            error.localizedDescription,
+		            "The operation could not be completed. The data isn’t in the correct format."
+		        )
+        	#else
+		        XCTAssertEqual(
+		            error.localizedDescription,
+		            "The data couldn’t be read because it isn’t in the correct format."
+		        )
+            #endif
         }
     }
 
@@ -122,10 +129,17 @@ final class JSONValueDecoderTests: XCTestCase {
                 from: JSONValue.hash(["int8": 300])
             )
         ) { error in
-            XCTAssertEqual(
-                error.localizedDescription,
-                "The data couldn’t be read because it isn’t in the correct format."
-            )
+        	#if os(Linux)
+                        XCTAssertEqual(
+		            error.localizedDescription,
+		            "The operation could not be completed. The data isn’t in the correct format."
+		        )
+        	#else
+		        XCTAssertEqual(
+		            error.localizedDescription,
+		            "The data couldn’t be read because it isn’t in the correct format."
+		        )
+            #endif
         }
     }
 
@@ -136,10 +150,17 @@ final class JSONValueDecoderTests: XCTestCase {
                 from: JSONValue.hash(["float": 1e300])
             )
         ) { error in
-            XCTAssertEqual(
-                error.localizedDescription,
-                "The data couldn’t be read because it isn’t in the correct format."
-            )
+        	#if os(Linux)
+                        XCTAssertEqual(
+		            error.localizedDescription,
+		            "The operation could not be completed. The data isn’t in the correct format."
+		        )
+        	#else
+		        XCTAssertEqual(
+		            error.localizedDescription,
+		            "The data couldn’t be read because it isn’t in the correct format."
+		        )
+            #endif
         }
     }
 }

Tests/JSONRPCTests/ProtocolTransportTests.swift

@@ -79,7 +79,7 @@ final class ProtocolTransportTests: XCTestCase {
         let result = JSONRPCNotification(method: "mynotification", params: params)
         let resultData = try JSONEncoder().encode(result)
 
-        XCTAssertEqual(dataTransport.writtenData, [resultData])
+        assertDataArraysEquals(dataTransport.writtenData, [resultData])
     }
 
 	@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
@@ -94,7 +94,16 @@ final class ProtocolTransportTests: XCTestCase {
 		let result = JSONRPCNotification(method: "mynotification", params: params)
 		let resultData = try JSONEncoder().encode(result)
 
-		XCTAssertEqual(dataTransport.writtenData, [resultData])
+		assertDataArraysEquals(dataTransport.writtenData, [resultData])
+	}
+
+	func assertDataArraysEquals(_ expr1: [Data], _ expr2: [Data]) {
+		XCTAssertEqual(expr1.count, expr2.count)
+		for idx in 0..<expr1.count {
+			let sorted1 = expr1[idx].sorted()
+			let sorted2 = expr2[idx].sorted()
+			XCTAssertEqual(sorted1, sorted2)
+		}
 	}
 
     func testServerToClientNotification() throws {