Add support for yield*

Change-Id: I5b054b59519ed825459a5b0b0a7cd2c6fc8a3797
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

7 files changed, 97 insertions, 3 deletions

diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index 7b1fd720a7..8747676685 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -286,6 +286,7 @@ ExecutionEngine::ExecutionEngine(QJSEngine *jsEngine)
     jsStrings[String_next] = newIdentifier(QStringLiteral("next"));
     jsStrings[String_done] = newIdentifier(QStringLiteral("done"));
     jsStrings[String_return] = newIdentifier(QStringLiteral("return"));
+    jsStrings[String_throw] = newIdentifier(QStringLiteral("throw"));
     jsStrings[String_global] = newIdentifier(QStringLiteral("global"));
     jsStrings[String_ignoreCase] = newIdentifier(QStringLiteral("ignoreCase"));
     jsStrings[String_multiline] = newIdentifier(QStringLiteral("multiline"));
diff --git a/src/qml/jsruntime/qv4engine_p.h b/src/qml/jsruntime/qv4engine_p.h
index 0b5d8663eb..276efe6e13 100644
--- a/src/qml/jsruntime/qv4engine_p.h
+++ b/src/qml/jsruntime/qv4engine_p.h
@@ -337,6 +337,7 @@ public:
         String_next,
         String_done,
         String_return,
+        String_throw,
         String_global,
         String_ignoreCase,
         String_multiline,
@@ -408,6 +409,7 @@ public:
     String *id_next() const { return reinterpret_cast<String *>(jsStrings + String_next); }
     String *id_done() const { return reinterpret_cast<String *>(jsStrings + String_done); }
     String *id_return() const { return reinterpret_cast<String *>(jsStrings + String_return); }
+    String *id_throw() const { return reinterpret_cast<String *>(jsStrings + String_throw); }
     String *id_global() const { return reinterpret_cast<String *>(jsStrings + String_global); }
     String *id_ignoreCase() const { return reinterpret_cast<String *>(jsStrings + String_ignoreCase); }
     String *id_multiline() const { return reinterpret_cast<String *>(jsStrings + String_multiline); }
diff --git a/src/qml/jsruntime/qv4generatorobject.cpp b/src/qml/jsruntime/qv4generatorobject.cpp
index 82d8d88882..dd3d0328b0 100644
--- a/src/qml/jsruntime/qv4generatorobject.cpp
+++ b/src/qml/jsruntime/qv4generatorobject.cpp
@@ -215,6 +215,7 @@ ReturnedValue GeneratorObject::resume(ExecutionEngine *engine, const Value &arg)
     const char *code = gp->cppFrame.yield;
     gp->cppFrame.yield = nullptr;
     gp->cppFrame.jsFrame->accumulator = arg;
+    gp->cppFrame.yieldIsIterator = false;
 
     Scope scope(engine);
     ScopedValue result(scope, Moth::VME::interpret(&gp->cppFrame, engine, code));
@@ -225,6 +226,8 @@ ReturnedValue GeneratorObject::resume(ExecutionEngine *engine, const Value &arg)
     gp->state = done ? GeneratorState::Completed : GeneratorState::SuspendedYield;
     if (engine->hasException)
         return Encode::undefined();
+    if (gp->cppFrame.yieldIsIterator)
+        return result->asReturnedValue();
     return IteratorPrototype::createIterResultObject(engine, result, done);
 }
 
diff --git a/src/qml/jsruntime/qv4runtime.cpp b/src/qml/jsruntime/qv4runtime.cpp
index 59fff91e7b..b59b9c3f50 100644
--- a/src/qml/jsruntime/qv4runtime.cpp
+++ b/src/qml/jsruntime/qv4runtime.cpp
@@ -782,6 +782,78 @@ ReturnedValue Runtime::method_iteratorNext(ExecutionEngine *engine, const Value
     return Encode(false);
 }
 
+ReturnedValue Runtime::method_iteratorNextForYieldStar(ExecutionEngine *engine, const Value &received, const Value &iterator, Value *object)
+{
+    // the return value encodes how to continue the yield* iteration.
+    // true implies iteration is done, false for iteration to continue
+    // a return value of undefines is a special marker, that the iterator has been invoked with return()
+
+    Scope scope(engine);
+    Q_ASSERT(iterator.isObject());
+
+    const Value *arg = &received;
+    bool returnCalled = false;
+    FunctionObject *f = nullptr;
+    if (engine->hasException) {
+        if (engine->exceptionValue->isEmpty()) {
+            // generator called with return()
+            *engine->exceptionValue = Encode::undefined();
+            engine->hasException = false;
+
+            ScopedValue ret(scope, static_cast<const Object &>(iterator).get(engine->id_return()));
+            if (ret->isUndefined()) {
+                // propagate return()
+                return Encode::undefined();
+            }
+            returnCalled = true;
+            f = ret->as<FunctionObject>();
+        } else {
+            // generator called with throw
+            ScopedValue exceptionValue(scope, *engine->exceptionValue);
+            *engine->exceptionValue = Encode::undefined();
+            engine->hasException = false;
+
+            ScopedValue t(scope, static_cast<const Object &>(iterator).get(engine->id_throw()));
+            if (engine->hasException)
+                return Encode::undefined();
+            if (t->isUndefined()) {
+                // no throw method on the iterator
+                ScopedValue done(scope, Encode(false));
+                method_iteratorClose(engine, iterator, done);
+                if (engine->hasException)
+                    return Encode::undefined();
+                return engine->throwTypeError();
+            }
+            f = t->as<FunctionObject>();
+            arg = exceptionValue;
+        }
+    } else {
+        // generator called with next()
+        ScopedFunctionObject next(scope, static_cast<const Object &>(iterator).get(engine->id_next()));
+        f = next->as<FunctionObject>();
+    }
+
+    if (!f)
+        return engine->throwTypeError();
+
+    ScopedObject o(scope, f->call(&iterator, arg, 1));
+    if (scope.hasException())
+        return Encode(true);
+    if (!o)
+        return engine->throwTypeError();
+
+    ScopedValue d(scope, o->get(engine->id_done()));
+    if (scope.hasException())
+        return Encode(true);
+    bool done = d->toBoolean();
+    if (done) {
+        *object = o->get(engine->id_value());
+        return returnCalled ? Encode::undefined() : Encode(true);
+    }
+    *object = o;
+    return Encode(false);
+}
+
 ReturnedValue Runtime::method_iteratorClose(ExecutionEngine *engine, const Value &iterator, const Value &done)
 {
     Q_ASSERT(iterator.isObject());
diff --git a/src/qml/jsruntime/qv4runtimeapi_p.h b/src/qml/jsruntime/qv4runtimeapi_p.h
index 62ba85efde..34b04929af 100644
--- a/src/qml/jsruntime/qv4runtimeapi_p.h
+++ b/src/qml/jsruntime/qv4runtimeapi_p.h
@@ -153,6 +153,7 @@ struct ExceptionCheck<void (*)(QV4::NoThrowEngine *, A, B, C)> {
     /* for-in, for-of and array destructuring */ \
     F(ReturnedValue, getIterator, (ExecutionEngine *engine, const Value &in, int iterator)) \
     F(ReturnedValue, iteratorNext, (ExecutionEngine *engine, const Value &iterator, Value *value)) \
+    F(ReturnedValue, iteratorNextForYieldStar, (ExecutionEngine *engine, const Value &received, const Value &iterator, Value *object)) \
     F(ReturnedValue, iteratorClose, (ExecutionEngine *engine, const Value &iterator, const Value &done)) \
     F(ReturnedValue, destructureRestElement, (ExecutionEngine *engine, const Value &iterator)) \
     \
diff --git a/src/qml/jsruntime/qv4stackframe_p.h b/src/qml/jsruntime/qv4stackframe_p.h
index ca39a8f7bb..39e7c25a4e 100644
--- a/src/qml/jsruntime/qv4stackframe_p.h
+++ b/src/qml/jsruntime/qv4stackframe_p.h
@@ -122,6 +122,7 @@ struct Q_QML_EXPORT CppStackFrame {
     const char *unwindHandler;
     const char *unwindLabel;
     int unwindLevel;
+    bool yieldIsIterator;
 
     void init(EngineBase *engine, Function *v4Function, const Value *argv, int argc) {
         this->engine = engine;
@@ -134,6 +135,7 @@ struct Q_QML_EXPORT CppStackFrame {
         unwindHandler = nullptr;
         unwindLabel = nullptr;
         unwindLevel = 0;
+        yieldIsIterator = false;
     }
 
     void push() {
diff --git a/src/qml/jsruntime/qv4vme_moth.cpp b/src/qml/jsruntime/qv4vme_moth.cpp
index 6ed371bbf2..07eb054350 100644
--- a/src/qml/jsruntime/qv4vme_moth.cpp
+++ b/src/qml/jsruntime/qv4vme_moth.cpp
@@ -661,9 +661,16 @@ QV4::ReturnedValue VME::interpret(CppStackFrame *frame, ExecutionEngine *engine,
 
     MOTH_BEGIN_INSTR(Yield)
         frame->yield = code;
+        frame->yieldIsIterator = false;
         return acc;
     MOTH_END_INSTR(Yield)
 
+    MOTH_BEGIN_INSTR(YieldStar)
+        frame->yield = code;
+        frame->yieldIsIterator = true;
+        return acc;
+    MOTH_END_INSTR(YieldStar)
+
     MOTH_BEGIN_INSTR(Resume)
         // check exception, in case the generator was called with throw() or return()
         if (engine->hasException) {
@@ -672,11 +679,17 @@ QV4::ReturnedValue VME::interpret(CppStackFrame *frame, ExecutionEngine *engine,
                 goto handleUnwind;
             engine->hasException = false;
             *engine->exceptionValue = Primitive::undefinedValue();
-    } else {
-        code += offset;
-    }
+        } else {
+            code += offset;
+        }
     MOTH_END_INSTR(Resume)
 
+    MOTH_BEGIN_INSTR(IteratorNextForYieldStar)
+        STORE_ACC();
+        acc = Runtime::method_iteratorNextForYieldStar(engine, accumulator, STACK_VALUE(iterator), &STACK_VALUE(object));
+        CHECK_EXCEPTION;
+    MOTH_END_INSTR(IteratorNextForYieldStar)
+
     MOTH_BEGIN_INSTR(CallValue)
         STORE_IP();
         Value func = STACK_VALUE(name);