Create extension on JSONDecoder to decode directly from JSON string

Author: mattt

Sources/SPMTestSupport/JSONDecoder+Extensions.swift

@@ -0,0 +1,22 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright (c) 2021 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See http://swift.org/LICENSE.txt for license information
+ See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+ */
+
+import Foundation
+
+extension JSONDecoder {
+    public func decode<T>(_ type: T.Type, from string: String) throws -> T where T : Decodable {
+        guard let data = string.data(using: .utf8) else {
+            let context = DecodingError.Context(codingPath: [], debugDescription: "invalid UTF-8 string")
+            throw DecodingError.dataCorrupted(context)
+        }
+
+        return try decode(type, from: data)
+    }
+}

Tests/PackageRegistryTests/RegistryConfigurationTests.swift

@@ -9,6 +9,7 @@
  */
 
 import XCTest
+import SPMTestSupport
 @testable import PackageRegistry
 
 private let defaultRegistryBaseURL = URL(string: "https://packages.example.com/")!
@@ -47,20 +48,20 @@ final class RegistryConfigurationTests: XCTestCase {
     }
 
     func testDecodeEmptyConfiguration() throws {
-        let data = #"""
+        let json = #"""
         {
             "registries": {},
             "version": 1
         }
-        """#.data(using: .utf8)!
+        """#
 
-        let configuration = try decoder.decode(RegistryConfiguration.self, from: data)
+        let configuration = try decoder.decode(RegistryConfiguration.self, from: json)
         XCTAssertNil(configuration.defaultRegistry)
         XCTAssertEqual(configuration.scopedRegistries, [:])
     }
 
     func testDecodeExampleConfiguration() throws {
-        let data = #"""
+        let json = #"""
         {
             "registries": {
                 "[default]": {
@@ -75,58 +76,58 @@ final class RegistryConfigurationTests: XCTestCase {
             },
             "version": 1
         }
-        """#.data(using: .utf8)!
+        """#
 
-        let configuration = try decoder.decode(RegistryConfiguration.self, from: data)
+        let configuration = try decoder.decode(RegistryConfiguration.self, from: json)
         XCTAssertEqual(configuration.defaultRegistry?.url, defaultRegistryBaseURL)
         XCTAssertEqual(configuration.scopedRegistries["foo"]?.url, customRegistryBaseURL)
         XCTAssertEqual(configuration.scopedRegistries["bar"]?.url, customRegistryBaseURL)
     }
 
     func testDecodeConfigurationWithInvalidRegistryKey() throws {
-        let data = #"""
+        let json = #"""
         {
             "registries": {
                 0: "\#(customRegistryBaseURL)"
             },
             "version": 1
         }
-        """#.data(using: .utf8)!
+        """#
 
-        XCTAssertThrowsError(try decoder.decode(RegistryConfiguration.self, from: data))
+        XCTAssertThrowsError(try decoder.decode(RegistryConfiguration.self, from: json))
     }
 
     func testDecodeConfigurationWithInvalidRegistryValue() throws {
-        let data = #"""
+        let json = #"""
         {
             "registries": {
                 "[default]": "\#(customRegistryBaseURL)"
             },
             "version": 1
         }
-        """#.data(using: .utf8)!
+        """#
 
-        XCTAssertThrowsError(try decoder.decode(RegistryConfiguration.self, from: data))
+        XCTAssertThrowsError(try decoder.decode(RegistryConfiguration.self, from: json))
     }
 
     func testDecodeConfigurationWithMissingVersion() throws {
-        let data = #"""
+        let json = #"""
         {
             "registries": {}
         }
-        """#.data(using: .utf8)!
+        """#
 
-        XCTAssertThrowsError(try decoder.decode(RegistryConfiguration.self, from: data))
+        XCTAssertThrowsError(try decoder.decode(RegistryConfiguration.self, from: json))
     }
 
     func testDecodeConfigurationWithInvalidVersion() throws {
-        let data = #"""
+        let json = #"""
         {
             "registries": {},
             "version": 999
         }
-        """#.data(using: .utf8)!
+        """#
 
-        XCTAssertThrowsError(try decoder.decode(RegistryConfiguration.self, from: data))
+        XCTAssertThrowsError(try decoder.decode(RegistryConfiguration.self, from: json))
     }
 }