Implement new spec changes for AsyncGenerator (#3950)

* Implement new spec changes for `AsyncGenerator`

* Add panic docs

Author: jedel1043

core/engine/src/builtins/async_generator/mod.rs

@@ -29,6 +29,10 @@ unsafe impl Trace for CompletionRecord {
 
 // ---- `CompletionRecord` methods ----
 impl CompletionRecord {
+    pub(crate) const fn is_throw_completion(&self) -> bool {
+        matches!(self, Self::Throw(_))
+    }
+
     /// This function will consume the current `CompletionRecord` and return a `JsResult<JsValue>`
     // NOTE: rustc bug around evaluating destructors that prevents this from being a const function.
     // Related issue(s):

core/engine/src/vm/completion_record.rs

@@ -48,16 +48,6 @@ impl Operation for Await {
 
         let gen = GeneratorContext::from_current(context);
 
-        // Even though it would be great to avoid cloning, we need to ensure
-        // the original async generator has a copy of the context in case it is resumed
-        // by a `return` or `throw` call instead of a continuation.
-        if let Some(async_generator) = gen.async_generator_object() {
-            async_generator
-                .downcast_mut::<AsyncGenerator>()
-                .expect("must be async generator")
-                .context = Some(gen.clone());
-        }
-
         let captures = Gc::new(Cell::new(Some(gen)));
 
         // 3. Let fulfilledClosure be a new Abstract Closure with parameters (value) that captures asyncContext and performs the following steps when called:
@@ -111,7 +101,6 @@ impl Operation for Await {
                     // d. Resume the suspended evaluation of asyncContext using ThrowCompletion(reason) as the result of the operation that suspended it.
                     // e. Assert: When we reach this step, asyncContext has already been removed from the execution context stack and prevContext is the currently running execution context.
                     // f. Return undefined.
-
                     let mut gen = captures.take().expect("should only run once");
 
                     // NOTE: We need to get the object before resuming, since it could clear the stack.

core/engine/src/vm/opcode/await/mod.rs

@@ -15,7 +15,7 @@ use crate::{
         opcode::{Operation, ReThrow},
         CallFrame, CompletionType,
     },
-    Context, JsError, JsObject, JsResult, JsValue,
+    Context, JsError, JsObject, JsResult,
 };
 
 pub(crate) use yield_stm::*;
@@ -128,26 +128,30 @@ impl Operation for AsyncGeneratorClose {
 
         let mut gen = generator.borrow_mut();
 
-        gen.data.state = AsyncGeneratorState::Completed;
-        gen.data.context = None;
+        // e. Assert: If we return here, the async generator either threw an exception or performed either an implicit or explicit return.
+        // f. Remove acGenContext from the execution context stack and restore the execution context that is at the top of the execution context stack as the running execution context.
 
-        let next = gen.data.queue.pop_front().expect("must have item in queue");
+        // g. Set acGenerator.[[AsyncGeneratorState]] to draining-queue.
+        gen.data.state = AsyncGeneratorState::DrainingQueue;
 
-        let return_value = context.vm.get_return_value();
-        context.vm.set_return_value(JsValue::undefined());
+        // h. If result is a normal completion, set result to NormalCompletion(undefined).
+        // i. If result is a return completion, set result to NormalCompletion(result.[[Value]]).
+        let return_value = context.vm.take_return_value();
 
-        let completion = context
+        let result = context
             .vm
             .pending_exception
             .take()
             .map_or(Ok(return_value), Err);
 
         drop(gen);
 
-        AsyncGenerator::complete_step(&next, completion, true, None, context);
-        // TODO: Upgrade to the latest spec when the problem is fixed.
-        AsyncGenerator::resume_next(&generator, context);
+        // j. Perform AsyncGeneratorCompleteStep(acGenerator, result, true).
+        AsyncGenerator::complete_step(&generator, result, true, None, context);
+        // k. Perform AsyncGeneratorDrainQueue(acGenerator).
+        AsyncGenerator::drain_queue(&generator, context);
 
+        // l. Return undefined.
         Ok(CompletionType::Normal)
     }
 }

core/engine/src/vm/opcode/generator/mod.rs

@@ -36,36 +36,40 @@ impl Operation for AsyncGeneratorYield {
     const COST: u8 = 8;
 
     fn execute(context: &mut Context) -> JsResult<CompletionType> {
-        let value = context.vm.pop();
+        // AsyncGeneratorYield ( value )
+        // https://tc39.es/ecma262/#sec-asyncgeneratoryield
 
+        // 1. Let genContext be the running execution context.
+        // 2. Assert: genContext is the execution context of a generator.
+        // 3. Let generator be the value of the Generator component of genContext.
+        // 4. Assert: GetGeneratorKind() is async.
         let async_generator_object = context
             .vm
             .frame()
             .async_generator_object(&context.vm.stack)
             .expect("`AsyncGeneratorYield` must only be called inside async generators");
-        let completion = Ok(value);
         let async_generator_object = async_generator_object
             .downcast::<AsyncGenerator>()
             .expect("must be async generator object");
-        let next = async_generator_object
-            .borrow_mut()
-            .data
-            .queue
-            .pop_front()
-            .expect("must have item in queue");
 
+        // 5. Let completion be NormalCompletion(value).
+        let value = context.vm.pop();
+        let completion = Ok(value);
+
+        // TODO: 6. Assert: The execution context stack has at least two elements.
         // TODO: 7. Let previousContext be the second to top element of the execution context stack.
-        AsyncGenerator::complete_step(&next, completion, false, None, context);
+        // TODO: 8. Let previousRealm be previousContext's Realm.
+        // 9. Perform AsyncGeneratorCompleteStep(generator, completion, false, previousRealm).
+        AsyncGenerator::complete_step(&async_generator_object, completion, false, None, context);
 
-        // TODO: Upgrade to the latest spec when the problem is fixed.
         let mut gen = async_generator_object.borrow_mut();
-        if gen.data.state == AsyncGeneratorState::Executing {
-            let Some(next) = gen.data.queue.front() else {
-                gen.data.state = AsyncGeneratorState::SuspendedYield;
-                context.vm.set_return_value(JsValue::undefined());
-                return Ok(CompletionType::Yield);
-            };
 
+        // 10. Let queue be generator.[[AsyncGeneratorQueue]].
+        // 11. If queue is not empty, then
+        //     a. NOTE: Execution continues without suspending the generator.
+        //     b. Let toYield be the first element of queue.
+        if let Some(next) = gen.data.queue.front() {
+            // c. Let resumptionValue be Completion(toYield.[[Completion]]).
             let resume_kind = match next.completion.clone() {
                 CompletionRecord::Normal(val) => {
                     context.vm.push(val);
@@ -84,17 +88,20 @@ impl Operation for AsyncGeneratorYield {
 
             context.vm.push(resume_kind);
 
+            // d. Return ? AsyncGeneratorUnwrapYieldResumption(resumptionValue).
             return Ok(CompletionType::Normal);
         }
 
-        assert!(matches!(
-            gen.data.state,
-            AsyncGeneratorState::AwaitingReturn | AsyncGeneratorState::Completed
-        ));
+        // 12. Else,
 
-        AsyncGenerator::resume_next(&async_generator_object, context);
+        //     a. Set generator.[[AsyncGeneratorState]] to suspended-yield.
+        gen.data.state = AsyncGeneratorState::SuspendedYield;
 
-        async_generator_object.borrow_mut().data.state = AsyncGeneratorState::SuspendedYield;
+        //     TODO: b. Remove genContext from the execution context stack and restore the execution context that is at the top of the execution context stack as the running execution context.
+        //     TODO: c. Let callerContext be the running execution context.
+        //     d. Resume callerContext passing undefined. If genContext is ever resumed again, let resumptionValue be the Completion Record with which it is resumed.
+        //     e. Assert: If control reaches here, then genContext is the running execution context again.
+        //     f. Return ? AsyncGeneratorUnwrapYieldResumption(resumptionValue).
         context.vm.set_return_value(JsValue::undefined());
         Ok(CompletionType::Yield)
     }

core/engine/src/vm/opcode/generator/yield_stm.rs

@@ -1,4 +1,4 @@
-commit = "3a7a72aef5009eb22117231d40f9a5a66a9a595a"
+commit = "12307f5c20a4c4211e69823939fd1872212894c5"
 
 [ignored]
 # Not implemented yet:
@@ -50,13 +50,25 @@ features = [
     # https://github.com/tc39/proposal-json-parse-with-source
     "json-parse-with-source",
 
+    # RegExp.escape
+    # https://github.com/tc39/proposal-regex-escaping
+    "RegExp.escape",
+
     # https://github.com/tc39/proposal-iterator-helpers
     "iterator-helpers",
 
     # Set methods
     # https://github.com/tc39/proposal-set-methods
     "set-methods",
 
+    # Uint8Array Base64
+    # https://github.com/tc39/proposal-arraybuffer-base64
+    "uint8array-base64",
+
+    # Atomics.pause
+    # https://github.com/tc39/proposal-atomics-microwait
+    "Atomics.pause",
+
     ### Non-standard
     "caller",
 ]

test262_config.toml

@@ -73,6 +73,10 @@ static FEATURE_EDITION: phf::Map<&'static str, SpecEdition> = phf::phf_map! {
     // https://github.com/tc39/proposal-json-parse-with-source
     "json-parse-with-source" => SpecEdition::ESNext,
 
+    // RegExp.escape
+    // https://github.com/tc39/proposal-regex-escaping
+    "RegExp.escape" => SpecEdition::ESNext,
+
     // Regular expression modifiers
     // https://github.com/tc39/proposal-regexp-modifiers
     "regexp-modifiers" => SpecEdition::ESNext,
@@ -85,10 +89,6 @@ static FEATURE_EDITION: phf::Map<&'static str, SpecEdition> = phf::phf_map! {
     // https://github.com/tc39/proposal-promise-try
     "promise-try" => SpecEdition::ESNext,
 
-    // Set methods
-    // https://github.com/tc39/proposal-set-methods
-    "set-methods" => SpecEdition::ESNext,
-
     // Explicit Resource Management
     // https://github.com/tc39/proposal-explicit-resource-management
     "explicit-resource-management" => SpecEdition::ESNext,
@@ -107,6 +107,14 @@ static FEATURE_EDITION: phf::Map<&'static str, SpecEdition> = phf::phf_map! {
     // test262 special specifier
     "source-phase-imports-module-source" => SpecEdition::ESNext,
 
+    // Uint8Array Base64
+    // https://github.com/tc39/proposal-arraybuffer-base64
+    "uint8array-base64" => SpecEdition::ESNext,
+
+    // Atomics.pause
+    // https://github.com/tc39/proposal-atomics-microwait
+    "Atomics.pause" => SpecEdition::ESNext,
+
     // Part of the next ES15 edition
     "Atomics.waitAsync"  => SpecEdition::ESNext,
     "regexp-v-flag" => SpecEdition::ESNext,
@@ -115,6 +123,7 @@ static FEATURE_EDITION: phf::Map<&'static str, SpecEdition> = phf::phf_map! {
     "resizable-arraybuffer" => SpecEdition::ESNext,
     "promise-with-resolvers" => SpecEdition::ESNext,
     "array-grouping" => SpecEdition::ESNext,
+    "set-methods" => SpecEdition::ESNext,
 
     // Standard language features
     "AggregateError" => SpecEdition::ES12,