Merge pull request #1327 from g4jc/async_iteration

Implement Async Iteration in SpiderMonkey

This resolves #1287

1 files changed, 93 insertions, 27 deletions

diff --git a/js/src/jsfun.cpp b/js/src/jsfun.cpp
index 9edf238ef..ce1ca33fe 100644
--- a/js/src/jsfun.cpp
+++ b/js/src/jsfun.cpp
@@ -41,6 +41,7 @@
 #include "js/CallNonGenericMethod.h"
 #include "js/Proxy.h"
 #include "vm/AsyncFunction.h"
+#include "vm/AsyncIteration.h"
 #include "vm/Debugger.h"
 #include "vm/GlobalObject.h"
 #include "vm/Interpreter.h"
@@ -131,7 +132,11 @@ IsFunctionInStrictMode(JSFunction* fun)
 
 static bool
 IsNewerTypeFunction(JSFunction* fun) {
-    return fun->isArrow() || fun->isGenerator() || fun->isAsync() || fun->isMethod();
+    return fun->isArrow() ||
+           fun->isStarGenerator() ||
+           fun->isLegacyGenerator() ||
+           fun->isAsync() ||
+           fun->isMethod();
 }
 
 // Beware: this function can be invoked on *any* function! That includes
@@ -308,6 +313,8 @@ CallerGetterImpl(JSContext* cx, const CallArgs& args)
         JSFunction* callerFun = &callerObj->as<JSFunction>();
         if (IsWrappedAsyncFunction(callerFun))
             callerFun = GetUnwrappedAsyncFunction(callerFun);
+        else if (IsWrappedAsyncGenerator(callerFun))
+            callerFun = GetUnwrappedAsyncGenerator(callerFun);
         MOZ_ASSERT(!callerFun->isBuiltin(), "non-builtin iterator returned a builtin?");
 
         if (callerFun->strict()) {
@@ -360,13 +367,15 @@ static const JSPropertySpec function_properties[] = {
 static bool
 ResolveInterpretedFunctionPrototype(JSContext* cx, HandleFunction fun, HandleId id)
 {
-    MOZ_ASSERT(fun->isInterpreted() || fun->isAsmJSNative());
+    bool isAsyncGenerator = IsWrappedAsyncGenerator(fun);
+
+    MOZ_ASSERT_IF(!isAsyncGenerator, fun->isInterpreted() || fun->isAsmJSNative());
     MOZ_ASSERT(id == NameToId(cx->names().prototype));
 
     // Assert that fun is not a compiler-created function object, which
     // must never leak to script or embedding code and then be mutated.
     // Also assert that fun is not bound, per the ES5 15.3.4.5 ref above.
-    MOZ_ASSERT(!IsInternalFunctionObject(*fun));
+    MOZ_ASSERT_IF(!isAsyncGenerator, !IsInternalFunctionObject(*fun));
     MOZ_ASSERT(!fun->isBoundFunction());
 
     // Make the prototype object an instance of Object with the same parent as
@@ -376,7 +385,9 @@ ResolveInterpretedFunctionPrototype(JSContext* cx, HandleFunction fun, HandleId
     bool isStarGenerator = fun->isStarGenerator();
     Rooted<GlobalObject*> global(cx, &fun->global());
     RootedObject objProto(cx);
-    if (isStarGenerator)
+    if (isAsyncGenerator)
+        objProto = GlobalObject::getOrCreateAsyncGeneratorPrototype(cx, global);
+    else if (isStarGenerator)
         objProto = GlobalObject::getOrCreateStarGeneratorObjectPrototype(cx, global);
     else
         objProto = GlobalObject::getOrCreateObjectPrototype(cx, global);
@@ -392,7 +403,7 @@ ResolveInterpretedFunctionPrototype(JSContext* cx, HandleFunction fun, HandleId
     // non-enumerable, and writable.  However, per the 15 July 2013 ES6 draft,
     // section 15.19.3, the .prototype of a generator function does not link
     // back with a .constructor.
-    if (!isStarGenerator) {
+    if (!isStarGenerator && !isAsyncGenerator) {
         RootedValue objVal(cx, ObjectValue(*fun));
         if (!DefineProperty(cx, proto, cx->names().constructor, objVal, nullptr, nullptr, 0))
             return false;
@@ -442,8 +453,14 @@ fun_resolve(JSContext* cx, HandleObject obj, HandleId id, bool* resolvedp)
          * - Arrow functions
          * - Function.prototype
          */
-        if (fun->isBuiltin() || (!fun->isConstructor() && !fun->isGenerator()))
-            return true;
+        if (!IsWrappedAsyncGenerator(fun)) {
+            if (fun->isBuiltin())
+                return true;
+            if (!fun->isConstructor()) {
+                if (!fun->isStarGenerator() && !fun->isLegacyGenerator() && !fun->isAsync())
+                    return true;
+            }
+        }
 
         if (!ResolveInterpretedFunctionPrototype(cx, fun, id))
             return false;
@@ -515,7 +532,7 @@ js::XDRInterpretedFunction(XDRState<mode>* xdr, HandleScope enclosingScope,
 {
     enum FirstWordFlag {
         HasAtom             = 0x1,
-        IsStarGenerator     = 0x2,
+        HasStarGeneratorProto = 0x2,
         IsLazy              = 0x4,
         HasSingletonType    = 0x8
     };
@@ -544,8 +561,8 @@ js::XDRInterpretedFunction(XDRState<mode>* xdr, HandleScope enclosingScope,
         if (fun->explicitName() || fun->hasCompileTimeName() || fun->hasGuessedAtom())
             firstword |= HasAtom;
 
-        if (fun->isStarGenerator())
-            firstword |= IsStarGenerator;
+        if (fun->isStarGenerator() || fun->isAsync())
+            firstword |= HasStarGeneratorProto;
 
         if (fun->isInterpretedLazy()) {
             // Encode a lazy script.
@@ -581,7 +598,7 @@ js::XDRInterpretedFunction(XDRState<mode>* xdr, HandleScope enclosingScope,
 
     if (mode == XDR_DECODE) {
         RootedObject proto(cx);
-        if (firstword & IsStarGenerator) {
+        if (firstword & HasStarGeneratorProto) {
             proto = GlobalObject::getOrCreateStarGeneratorFunctionPrototype(cx, cx->global());
             if (!proto)
                 return false;
@@ -938,6 +955,11 @@ js::FunctionToString(JSContext* cx, HandleFunction fun, bool prettyPrint)
         return FunctionToString(cx, unwrapped, prettyPrint);
     }
 
+    if (IsWrappedAsyncGenerator(fun)) {
+        RootedFunction unwrapped(cx, GetUnwrappedAsyncGenerator(fun));
+        return FunctionToString(cx, unwrapped, prettyPrint);
+    }
+
     StringBuffer out(cx);
     RootedScript script(cx);
 
@@ -1556,7 +1578,7 @@ fun_isGenerator(JSContext* cx, unsigned argc, Value* vp)
         return true;
     }
 
-    args.rval().setBoolean(fun->isGenerator());
+    args.rval().setBoolean(fun->isStarGenerator() || fun->isLegacyGenerator());
     return true;
 }
 
@@ -1588,8 +1610,6 @@ FunctionConstructor(JSContext* cx, const CallArgs& args, GeneratorKind generator
     bool isStarGenerator = generatorKind == StarGenerator;
     bool isAsync = asyncKind == AsyncFunction;
     MOZ_ASSERT(generatorKind != LegacyGenerator);
-    MOZ_ASSERT_IF(isAsync, isStarGenerator);
-    MOZ_ASSERT_IF(!isStarGenerator, !isAsync);
 
     RootedScript maybeScript(cx);
     const char* filename;
@@ -1600,10 +1620,14 @@ FunctionConstructor(JSContext* cx, const CallArgs& args, GeneratorKind generator
                                          &mutedErrors);
 
     const char* introductionType = "Function";
-    if (isAsync)
-        introductionType = "AsyncFunction";
-    else if (generatorKind != NotGenerator)
+    if (isAsync) {
+        if (isStarGenerator)
+            introductionType = "AsyncGenerator";
+        else
+            introductionType = "AsyncFunction";
+    } else if (generatorKind != NotGenerator) {
         introductionType = "GeneratorFunction";
+    }
 
     const char* introducerFilename = filename;
     if (maybeScript && maybeScript->scriptSource()->introducerFilename())
@@ -1701,7 +1725,7 @@ FunctionConstructor(JSContext* cx, const CallArgs& args, GeneratorKind generator
 
     // Step 4.d, use %Generator% as the fallback prototype.
     // Also use %Generator% for the unwrapped function of async functions.
-    if (!proto && isStarGenerator) {
+    if (!proto && (isStarGenerator || isAsync)) {
         proto = GlobalObject::getOrCreateStarGeneratorFunctionPrototype(cx, global);
         if (!proto)
             return false;
@@ -1731,12 +1755,20 @@ FunctionConstructor(JSContext* cx, const CallArgs& args, GeneratorKind generator
                                               : SourceBufferHolder::NoOwnership;
     bool ok;
     SourceBufferHolder srcBuf(chars.begin().get(), chars.length(), ownership);
-    if (isAsync)
-        ok = frontend::CompileStandaloneAsyncFunction(cx, &fun, options, srcBuf, parameterListEnd);
-    else if (isStarGenerator)
-        ok = frontend::CompileStandaloneGenerator(cx, &fun, options, srcBuf, parameterListEnd);
-    else
-        ok = frontend::CompileStandaloneFunction(cx, &fun, options, srcBuf, parameterListEnd);
+    if (isAsync) {
+        if (isStarGenerator) {
+            ok = frontend::CompileStandaloneAsyncGenerator(cx, &fun, options, srcBuf,
+                                                           parameterListEnd);
+        } else {
+            ok = frontend::CompileStandaloneAsyncFunction(cx, &fun, options, srcBuf,
+                                                          parameterListEnd);
+        }
+    } else {
+        if (isStarGenerator)
+            ok = frontend::CompileStandaloneGenerator(cx, &fun, options, srcBuf, parameterListEnd);
+        else
+            ok = frontend::CompileStandaloneFunction(cx, &fun, options, srcBuf, parameterListEnd);
+    }
 
     // Step 33.
     args.rval().setObject(*fun);
@@ -1762,14 +1794,14 @@ js::AsyncFunctionConstructor(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
 
-    // Save the callee before its reset in FunctionConstructor().
+    // Save the callee before it's reset in FunctionConstructor().
     RootedObject newTarget(cx);
     if (args.isConstructing())
         newTarget = &args.newTarget().toObject();
     else
         newTarget = &args.callee();
 
-    if (!FunctionConstructor(cx, args, StarGenerator, AsyncFunction))
+    if (!FunctionConstructor(cx, args, NotGenerator, AsyncFunction))
         return false;
 
     // ES2017, draft rev 0f10dba4ad18de92d47d421f378233a2eae8f077
@@ -1795,6 +1827,40 @@ js::AsyncFunctionConstructor(JSContext* cx, unsigned argc, Value* vp)
 }
 
 bool
+js::AsyncGeneratorConstructor(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Save the callee before its reset in FunctionConstructor().
+    RootedObject newTarget(cx);
+    if (args.isConstructing())
+        newTarget = &args.newTarget().toObject();
+    else
+        newTarget = &args.callee();
+
+    if (!FunctionConstructor(cx, args, StarGenerator, AsyncFunction))
+        return false;
+
+    RootedObject proto(cx);
+    if (!GetPrototypeFromConstructor(cx, newTarget, &proto))
+        return false;
+
+    if (!proto) {
+        proto = GlobalObject::getOrCreateAsyncGenerator(cx, cx->global());
+        if (!proto)
+            return false;
+    }
+
+    RootedFunction unwrapped(cx, &args.rval().toObject().as<JSFunction>());
+    RootedObject wrapped(cx, WrapAsyncGeneratorWithProto(cx, unwrapped, proto));
+    if (!wrapped)
+        return false;
+
+    args.rval().setObject(*wrapped);
+    return true;
+}
+
+bool
 JSFunction::isBuiltinFunctionConstructor()
 {
     return maybeNative() == Function || maybeNative() == Generator;
@@ -1965,7 +2031,7 @@ NewFunctionClone(JSContext* cx, HandleFunction fun, NewObjectKind newKind,
                  gc::AllocKind allocKind, HandleObject proto)
 {
     RootedObject cloneProto(cx, proto);
-    if (!proto && fun->isStarGenerator()) {
+    if (!proto && (fun->isStarGenerator() || fun->isAsync())) {
         cloneProto = GlobalObject::getOrCreateStarGeneratorFunctionPrototype(cx, cx->global());
         if (!cloneProto)
             return nullptr;