Add partial support for yield via experimental flag (#1815)

Author: lahma

Jint.Tests.Test262/Test262Harness.settings.json

@@ -15,6 +15,7 @@ private Engine BuildTestExecutor(Test262File file)
         {
             var relativePath = Path.GetDirectoryName(file.FileName);
             cfg.EnableModules(new Test262ModuleLoader(State.Test262Stream.Options.FileSystem, relativePath));
+            cfg.ExperimentalFeatures = ExperimentalFeature.All;
         });
 
         if (file.Flags.Contains("raw"))

Jint.Tests.Test262/Test262Test.cs

@@ -0,0 +1,251 @@
+namespace Jint.Tests.Runtime;
+
+public class GeneratorTests
+{
+    private readonly Engine _engine;
+
+    public GeneratorTests()
+    {
+        _engine = new Engine(options => options.ExperimentalFeatures = ExperimentalFeature.Generators);
+    }
+
+    [Fact]
+    public void LoopYield()
+    {
+        const string Script = """
+          const foo = function*() {
+            yield 'a';
+            yield 'b';
+            yield 'c';
+          };
+
+          let str = '';
+          for (const val of foo()) {
+            str += val;
+          }
+          return str;
+      """;
+
+        Assert.Equal("abc", _engine.Evaluate(Script));
+    }
+
+    [Fact]
+    public void ReturnDuringYield()
+    {
+        const string Script = """
+          const foo = function*() {
+            yield 'a';
+            return;
+            yield 'c';
+          };
+
+          let str = '';
+          for (const val of foo()) {
+            str += val;
+          }
+          return str;
+      """;
+
+        Assert.Equal("a", _engine.Evaluate(Script));
+    }
+
+    [Fact]
+    public void LoneReturnInYield()
+    {
+        const string Script = """
+          const foo = function*() {
+            return;
+          };
+
+          let str = '';
+          for (const val of foo()) {
+            str += val;
+          }
+          return str;
+      """;
+
+        Assert.Equal("", _engine.Evaluate(Script));
+    }
+
+    [Fact]
+    public void LoneReturnValueInYield()
+    {
+        const string Script = """
+          const foo = function*() {
+            return 'a';
+          };
+
+          let str = '';
+          for (const val of foo()) {
+            str += val;
+          }
+          return str;
+      """;
+
+        Assert.Equal("", _engine.Evaluate(Script));
+    }
+
+    [Fact]
+    public void YieldUndefined()
+    {
+        const string Script = """
+          const foo = function*() {
+            yield undefined;
+          };
+
+          let str = '';
+          for (const val of foo()) {
+            str += val;
+          }
+          return str;
+      """;
+
+        Assert.Equal("undefined", _engine.Evaluate(Script));
+    }
+
+    [Fact]
+    public void ReturnUndefined()
+    {
+        const string Script = """
+          const foo = function*() {
+            return undefined;
+          };
+
+          let str = '';
+          for (const val of foo()) {
+            str += val;
+          }
+          return str;
+      """;
+
+        Assert.Equal("", _engine.Evaluate(Script));
+    }
+
+    [Fact]
+    public void Basic()
+    {
+        _engine.Execute("function * generator() { yield 5; yield 6; };");
+        _engine.Execute("var iterator = generator(); var item = iterator.next();");
+        Assert.Equal(5, _engine.Evaluate("item.value"));
+        Assert.False(_engine.Evaluate("item.done").AsBoolean());
+        _engine.Execute("item = iterator.next();");
+        Assert.Equal(6, _engine.Evaluate("item.value"));
+        Assert.False(_engine.Evaluate("item.done").AsBoolean());
+        _engine.Execute("item = iterator.next();");
+        Assert.True(_engine.Evaluate("item.value === void undefined").AsBoolean());
+        Assert.True(_engine.Evaluate("item.done").AsBoolean());
+    }
+
+    [Fact]
+    public void FunctionExpressions()
+    {
+        _engine.Execute("var generator = function * () { yield 5; yield 6; };");
+        _engine.Execute("var iterator = generator(); var item = iterator.next();");
+        Assert.Equal(5, _engine.Evaluate("item.value"));
+        Assert.False(_engine.Evaluate("item.done").AsBoolean());
+        _engine.Execute("item = iterator.next();");
+        Assert.Equal(6, _engine.Evaluate("item.value"));
+        Assert.False(_engine.Evaluate("item.done").AsBoolean());
+        _engine.Execute("item = iterator.next();");
+        Assert.True(_engine.Evaluate("item.value === void undefined").AsBoolean());
+        Assert.True(_engine.Evaluate("item.done").AsBoolean());
+    }
+
+    [Fact]
+    public void CorrectThisBinding()
+    {
+        _engine.Execute("var generator = function * () { yield 5; yield 6; };");
+        _engine.Execute("var iterator = { g: generator, x: 5, y: 6 }.g(); var item = iterator.next();");
+        Assert.Equal(5, _engine.Evaluate("item.value"));
+        Assert.False(_engine.Evaluate("item.done").AsBoolean());
+        _engine.Execute("item = iterator.next();");
+        Assert.Equal(6, _engine.Evaluate("item.value"));
+        Assert.False(_engine.Evaluate("item.done").AsBoolean());
+        _engine.Execute("item = iterator.next();");
+        Assert.True(_engine.Evaluate("item.value === void undefined").AsBoolean());
+        Assert.True(_engine.Evaluate("item.done").AsBoolean());
+    }
+
+    [Fact(Skip = "TODO es6-generators")]
+    public void Sending()
+    {
+        const string Script = """
+          var sent;
+          function * generator() {
+            sent = [yield 5, yield 6];
+          };
+          var iterator = generator();
+          iterator.next();
+          iterator.next("foo");
+          iterator.next("bar");
+        """;
+
+        _engine.Execute(Script);
+
+        Assert.Equal("foo", _engine.Evaluate("sent[0]"));
+        Assert.Equal("bar", _engine.Evaluate("sent[1]"));
+    }
+
+    [Fact(Skip = "TODO es6-generators")]
+    public void Sending2()
+    {
+        const string Script = """
+        function* counter(value) {
+          while (true) {
+            const step = yield value++;
+        
+            if (step) {
+              value += step;
+            }
+          }
+        }
+        
+        const generatorFunc = counter(0);
+        """;
+
+        _engine.Execute(Script);
+
+        Assert.Equal(0, _engine.Evaluate("generatorFunc.next().value")); // 0
+        Assert.Equal(1, _engine.Evaluate("generatorFunc.next().value")); // 1
+        Assert.Equal(2, _engine.Evaluate("generatorFunc.next().value")); // 2
+        Assert.Equal(3, _engine.Evaluate("generatorFunc.next().value")); // 3
+        Assert.Equal(14, _engine.Evaluate("generatorFunc.next(10).value")); // 14
+        Assert.Equal(15, _engine.Evaluate("generatorFunc.next().value")); // 15
+        Assert.Equal(26, _engine.Evaluate("generatorFunc.next(10).value")); // 26
+    }
+
+    [Fact(Skip = "TODO es6-generators")]
+    public void Fibonacci()
+    {
+        const string Script = """
+            function* fibonacci() {
+              let current = 0;
+              let next = 1;
+              while (true) {
+                const reset = yield current;
+                [current, next] = [next, next + current];
+                if (reset) {
+                  current = 0;
+                  next = 1;
+                }
+              }
+            }
+            
+            const sequence = fibonacci();
+        """;
+
+        _engine.Execute(Script);
+
+        Assert.Equal(0, _engine.Evaluate("sequence.next().value"));
+        Assert.Equal(1, _engine.Evaluate("sequence.next().value"));
+        Assert.Equal(1, _engine.Evaluate("sequence.next().value"));
+        Assert.Equal(2, _engine.Evaluate("sequence.next().value"));
+        Assert.Equal(3, _engine.Evaluate("sequence.next().value"));
+        Assert.Equal(5, _engine.Evaluate("sequence.next().value"));
+        Assert.Equal(9, _engine.Evaluate("sequence.next().value"));
+        Assert.Equal(0, _engine.Evaluate("sequence.next(true).value"));
+        Assert.Equal(1, _engine.Evaluate("sequence.next().value)"));
+        Assert.Equal(1, _engine.Evaluate("sequence.next().value)"));
+        Assert.Equal(2, _engine.Evaluate("sequence.next().value)"));
+    }
+}