Create Jint engines through a configuration service

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 - Fixed background thread leaks when worker construction is rejected
 - Fixed canonical DOM node identity and concrete prototypes through `DomSameObject` getters (#140)
+- Added `JsScriptingOptions.EngineCreator` to create a configured Jint engine before any page script runs
 
 # 1.1.0
 

README.md

@@ -46,6 +46,29 @@ var config = Configuration.Default
     });
 ```
 
+Register an `EngineCreator` service to configure Jint before inline page scripts run:
+
+```cs
+using Jint;
+using AngleSharp.Js;
+
+var config = Configuration.Default
+    .With(new EngineCreator((window, options) => new Engine(options
+        .MaxStatements(100_000)
+        .TimeoutInterval(TimeSpan.FromSeconds(5))
+        .LimitMemory(16 * 1024 * 1024))))
+    .WithJs();
+```
+
+The factory runs once for each window and must return a fresh engine using the supplied options.
+Those options contain AngleSharp's DOM module loader, object wrapper, and call stack guard.
+DOM bindings are installed after the factory returns. Configure the engine and host globals
+in the factory, then access DOM objects and evaluate page scripts through the document.
+Jint controls the scope and reset behavior of its constraints.
+Any state captured by the service remains owned by the host.
+Hosts sharing one configuration across windows must make
+their captured state safe for that use.
+
 You can also use this part with a console for logging. The call for this is `WithConsoleLogger`, e.g.,
 
 ```cs

src/AngleSharp.Js.Tests/EngineConfigurationTests.cs

@@ -0,0 +1,165 @@
+namespace AngleSharp.Js.Tests
+{
+    using AngleSharp.Dom;
+    using AngleSharp.Io;
+    using AngleSharp.Js.Tests.Mocks;
+    using AngleSharp.Scripting;
+    using Jint;
+    using Jint.Runtime;
+    using NUnit.Framework;
+    using System;
+    using System.Collections.Concurrent;
+    using System.Threading;
+    using System.Threading.Tasks;
+
+    public class EngineConfigurationTests
+    {
+        [Test]
+        public async Task ConstraintsAreInstalledBeforeInlineScriptsRun()
+        {
+            var config = Configuration.Default
+                .With(new EngineCreator((window, options) => new Engine(options.MaxStatements(64))))
+                .WithJs()
+                .WithEventLoop();
+
+            using (var context = BrowsingContext.New(config))
+            {
+                var document = await context.OpenAsync(request => request.Content(
+                    "<div id='result'>before</div><script>for (var i = 0; i < 1000; i++) {} " +
+                    "document.getElementById('result').textContent = 'after';</script>")).ConfigureAwait(false);
+
+                Assert.AreEqual("before", document.QuerySelector("#result").TextContent);
+                Assert.Throws<StatementsCountOverflowException>(() => document.ExecuteScript(
+                    "for (var i = 0; i < 1000; i++) {}"));
+                Assert.AreEqual("before", document.ExecuteScript("document.getElementById('result').textContent"));
+            }
+        }
+
+        [Test]
+        public async Task CreatorServiceCanBeCreatedForEachBrowsingContext()
+        {
+            var services = 0;
+            Func<IBrowsingContext, EngineCreator> createService = _ =>
+            {
+                services++;
+                var limit = services == 1 ? 64 : 2000;
+                return (window, options) => new Engine(options.MaxStatements(limit));
+            };
+            var config = Configuration.Default.With(createService).WithJs().WithEventLoop();
+
+            using (var first = BrowsingContext.New(config))
+            using (var second = BrowsingContext.New(config))
+            {
+                var firstDocument = await first.OpenNewAsync().ConfigureAwait(false);
+                var secondDocument = await second.OpenNewAsync().ConfigureAwait(false);
+                Assert.Throws<StatementsCountOverflowException>(() => firstDocument.ExecuteScript(
+                    "for (var i = 0; i < 1000; i++) {}"));
+                Assert.AreEqual(100, secondDocument.ExecuteScript("var i = 0; for (; i < 100; i++) {} i;"));
+                Assert.AreEqual(2, services);
+            }
+        }
+
+        [Test]
+        public async Task CreatorRunsOncePerWindowAndRetainsDomWrapping()
+        {
+            var calls = 0;
+            var windows = new ConcurrentQueue<IWindow>();
+            var config = Configuration.Default.With(new EngineCreator((window, options) =>
+            {
+                calls++;
+                windows.Enqueue(window);
+                return new Engine(options.MaxStatements(1000));
+            })).WithJs().WithEventLoop();
+
+            using (var firstContext = BrowsingContext.New(config))
+            using (var secondContext = BrowsingContext.New(config))
+            {
+                var first = await firstContext.OpenAsync(request => request.Content("<p>first</p>")).ConfigureAwait(false);
+                var second = await secondContext.OpenAsync(request => request.Content("<p>second</p>")).ConfigureAwait(false);
+
+                Assert.AreEqual("first", first.ExecuteScript("document.querySelector('p').textContent"));
+                Assert.AreEqual("first", first.ExecuteScript("document.querySelector('p').textContent"));
+                Assert.AreEqual("second", second.ExecuteScript("document.querySelector('p').textContent"));
+                Assert.AreEqual(2, calls);
+                CollectionAssert.AreEqual(new[] { first.DefaultView, second.DefaultView }, windows.ToArray());
+            }
+        }
+
+        [Test]
+        public async Task CreatorReturnsTheEngineUsedForInlineScriptsAndDomBindings()
+        {
+            Engine created = null;
+            var config = Configuration.Default.With(new EngineCreator((window, options) =>
+            {
+                created = new Engine(options.Configure(engine => engine.SetValue("hostValue", "configured")));
+                return created;
+            })).WithJs().WithEventLoop();
+
+            using (var context = BrowsingContext.New(config))
+            {
+                var document = await context.OpenAsync(request => request.Content(
+                    "<p>before</p><script>document.querySelector('p').textContent = hostValue;</script>")).ConfigureAwait(false);
+                Assert.AreEqual("configured", document.QuerySelector("p").TextContent);
+                Assert.AreSame(created, context.GetService<JsScriptingService>().GetOrCreateJint(document));
+                created.SetValue("hostNode", document.QuerySelector("p"));
+                Assert.AreEqual(true, document.ExecuteScript("hostNode === document.querySelector('p')"));
+            }
+        }
+
+        [TestCase(false)]
+        [TestCase(true)]
+        public async Task WorkersInheritTheEngineCreatorService(Boolean contextFactory)
+        {
+            var services = 0;
+            var windows = new ConcurrentQueue<IWindow>();
+            EngineCreator CreateEngine(String hostValue) => (window, options) =>
+            {
+                windows.Enqueue(window);
+                return new Engine(options.MaxStatements(256)
+                    .Configure(engine => engine.SetValue("hostValue", hostValue)));
+            };
+            Object registration = contextFactory
+                ? (Object)new Func<IBrowsingContext, EngineCreator>(_ => CreateEngine("context-" + Interlocked.Increment(ref services)))
+                : CreateEngine("configured");
+            var config = Configuration.Default
+                .With(registration)
+                .WithJs()
+                .WithEventLoop()
+                .With(new DelayedRequester(0, "self.__host = hostValue; for (var i = 0; i < 10000; i++) {} self.__after = true;"))
+                .WithDefaultLoader(new LoaderOptions { IsResourceLoadingEnabled = true });
+
+            using (var context = BrowsingContext.New(config))
+            {
+                var document = await context.OpenNewAsync().ConfigureAwait(false);
+                Assert.AreEqual(contextFactory ? "context-1" : "configured", document.ExecuteScript("hostValue"));
+                var worker = new Dom.Worker(document.DefaultView, "https://example.com/worker.js");
+
+                try
+                {
+                    for (var retries = 200; retries > 0 && !worker.IsInitialized && worker.StartupError is null; retries--)
+                    {
+                        await Task.Delay(10).ConfigureAwait(false);
+                    }
+
+                    Assert.IsInstanceOf<StatementsCountOverflowException>(worker.StartupError);
+                    Assert.AreEqual(contextFactory ? "context-2" : "configured", worker.EvaluateInWorker("self.__host"));
+                    Assert.AreEqual("undefined", worker.EvaluateInWorker("typeof self.__after"));
+                    var createdWindows = windows.ToArray();
+                    Assert.AreEqual(2, createdWindows.Length);
+                    Assert.AreSame(document.DefaultView, createdWindows[0]);
+                    Assert.AreNotSame(document.DefaultView, createdWindows[1]);
+                    Assert.AreNotSame(context, createdWindows[1].Document.Context);
+                    Assert.AreSame(createdWindows[1], createdWindows[1].Document.DefaultView);
+                    if (contextFactory)
+                    {
+                        Assert.AreEqual(2, services);
+                    }
+                }
+                finally
+                {
+                    worker.Terminate();
+                }
+            }
+        }
+    }
+}

src/AngleSharp.Js/Dom/Worker.cs

@@ -72,6 +72,15 @@ public Worker(IWindow window, String source)
                 var workerConfig = Configuration.Default
                     .With(_scripting)
                     .WithOnly(_workerLoop);
+
+                foreach (var service in parentContext.OriginalServices)
+                {
+                    if (service is EngineCreator || service is Func<IBrowsingContext, EngineCreator>)
+                    {
+                        workerConfig = workerConfig.With(service);
+                    }
+                }
+
                 _workerContext = BrowsingContext.New(workerConfig);
 
                 Enqueue(_workerLoop, TaskPriority.Critical, () =>

src/AngleSharp.Js/EngineCreator.cs

@@ -0,0 +1,17 @@
+namespace AngleSharp.Js
+{
+    using AngleSharp.Dom;
+
+    /// <summary>
+    /// Creates a window's Jint engine. Register this service with the configuration
+    /// to customize engine creation before page scripts run.
+    /// </summary>
+    /// <param name="window">The window whose engine is being created.</param>
+    /// <param name="options">Options containing the DOM wrapper, module loader, and stack guard.</param>
+    /// <returns>A fresh engine constructed with the supplied options.</returns>
+    /// <remarks>
+    /// DOM bindings are installed after this delegate returns. Configure the engine
+    /// and host globals here; access DOM objects and run page scripts afterwards.
+    /// </remarks>
+    public delegate Jint.Engine EngineCreator(IWindow window, Jint.Options options);
+}

src/AngleSharp.Js/EngineInstance.cs

@@ -37,21 +37,17 @@ sealed class EngineInstance
         public EngineInstance(IWindow window, IDictionary<String, Object> assignments, IEnumerable<Assembly> libs, JsScriptingOptions options)
         {
             _importMap = new JsImportMap();
-
-            _engine = new Engine((o) =>
-            {
-                o.EnableModules(new JsModuleLoader(this, window.Document, false));
-                //  The handler answers out of the caches assigned right below, which only exist
-                //  once this constructor returns. Jint wraps nothing while it is configuring
-                //  itself, so that is safe - and Engine.Options is internal, so registering the
-                //  handler afterwards is not an option.
-                o.SetWrapObjectHandler(WrapObject);
-                //  Left alone, the JS call stack is the native one, and a script recursing
-                //  deeper than it holds takes the whole process down - a StackOverflowException
-                //  cannot be caught. Guarded, the engine continues on a fresh stack and finally
-                //  reports an ordinary "Maximum call stack size exceeded" error instead.
-                o.Constraints.MaxExecutionStackCount = options.MaxCallStackDepth > 0 ? options.MaxCallStackDepth : StackGuardDisabled;
-            });
+            var engineOptions = new Options();
+            engineOptions.EnableModules(new JsModuleLoader(this, window.Document, false));
+            // The handler uses the caches initialized below. The creator must return the
+            // engine before DOM objects are wrapped or page scripts are evaluated.
+            engineOptions.SetWrapObjectHandler(WrapObject);
+            // Left alone, the JS call stack is the native one, and a runaway recursion
+            // takes the process down with an uncatchable StackOverflowException.
+            engineOptions.Constraints.MaxExecutionStackCount = options.MaxCallStackDepth > 0 ? options.MaxCallStackDepth : StackGuardDisabled;
+            var creator = window.Document.Context.GetService<EngineCreator>();
+            _engine = (creator is null ? new Engine(engineOptions) : creator.Invoke(window, engineOptions))
+                ?? throw new InvalidOperationException("The engine creator must return a Jint engine.");
             _libs = new LibrarySet(libs);
             _prototypes = new PrototypeCache(_engine, _libs);
             _references = new ReferenceCache();