Add Init() APIs

Author: mythz

src/ServiceStack.Text/Env.cs

@@ -140,7 +140,11 @@ static Env()
         public static bool StrictMode
         {
             get => strictMode;
-            set => JsConfig.ThrowOnError = strictMode = value;
+            set
+            {
+                strictMode = value;
+                if (!JsConfig.HasInit) JsConfig.ThrowOnError = value;
+            }
         }
 
         public static string ServerUserAgent { get; set; }

src/ServiceStack.Text/JsConfig.cs

@@ -25,6 +25,20 @@ static JsConfig()
         // force deterministic initialization of static constructor
         public static void InitStatics() { }
 
+        /// <summary>
+        /// Mark JsConfig global config as initialized and assert it's no longer mutated
+        /// </summary>
+        /// <param name="config"></param>
+        public static void Init() => Config.Init();
+        
+        /// <summary>
+        /// Initialize global config and assert that it's no longer mutated 
+        /// </summary>
+        /// <param name="config"></param>
+        public static void Init(Config config) => Config.Init(config);
+
+        public static bool HasInit => Config.HasInit;
+
         public static JsConfigScope BeginScope()
         {
             return new JsConfigScope(); //Populated with Config.Instance

src/ServiceStack.Text/JsConfigScope.cs

@@ -51,9 +51,26 @@ public static Config AssertNotInit() => HasInit
             ? throw new NotSupportedException("JsConfig can't be mutated after JsConfig.Init(). Use BeginScope() or CreateScope() to use custom config after Init().")
             : Instance;
 
-        public static void Init() => HasInit = true;
+        private static string InitStackTrace = null;
 
-        internal static void Reset() => Instance.Populate(Defaults);
+        public static void Init() => Init(null);
+        public static void Init(Config config)
+        {
+            if (HasInit && Env.StrictMode)
+                throw new NotSupportedException($"JsConfig has already been initialized at: {InitStackTrace}");
+            
+            if (config != null)
+                instance = config;
+
+            HasInit = true;
+            InitStackTrace = Environment.StackTrace;
+        }
+
+        internal static void Reset()
+        {
+            HasInit = false;
+            Instance.Populate(Defaults);
+        }
 
         public Config()
         {

tests/ServiceStack.Text.Tests/JsConfigTests.cs

@@ -244,4 +244,53 @@ public void Does_create_scope_from_string_using_CamelCaseHumps()
             scope.Dispose();
         }
     }
+
+    public class JsConfigInitTests
+    {
+        [TearDown] public void TearDown() => JsConfig.Reset();
+        
+        [Test]
+        public void Allows_setting_config_before_Init()
+        {
+            JsConfig.MaxDepth = 1;
+            JsConfig.Init(new Config {
+                DateHandler = DateHandler.UnixTime
+            });
+        }
+        
+        [Test]
+        public void Does_not_allow_setting_JsConfig_after_Init()
+        {
+            JsConfig.Init(new Config {
+                DateHandler = DateHandler.UnixTime
+            });
+
+            Assert.Throws<NotSupportedException>(() => JsConfig.MaxDepth = 1000);
+        }
+
+        [Test]
+        public void Does_not_allow_setting_multiple_inits_in_StrictMode()
+        {
+            JsConfig.Init();
+            JsConfig.Init(new Config { MaxDepth = 1 });
+
+            Env.StrictMode = true;
+            
+            Assert.Throws<NotSupportedException>(() => JsConfig.Init());
+        }
+
+        [Test]
+        public void Does_combine_global_configs_in_multiple_inits()
+        {
+            JsConfig.Init(new Config { MaxDepth = 1 });
+            JsConfig.Init(new Config { DateHandler = DateHandler.UnixTime });
+            
+            Assert.That(JsConfig.MaxDepth, Is.EqualTo(1));
+            Assert.That(JsConfig.DateHandler, Is.EqualTo(DateHandler.UnixTime));
+
+            var newConfig = new Config();
+            Assert.That(newConfig.MaxDepth, Is.EqualTo(1));
+            Assert.That(newConfig.DateHandler, Is.EqualTo(DateHandler.UnixTime));
+        }
+    }
 }