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Fix rewrite of nested async arrow functions that have references to "…
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…this", "super" or "arguments".

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=185432876
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@SergejSalnikov @brad4d
SergejSalnikov authored and brad4d committed Feb 13, 2018
1 parent cbbee4a commit 8f8b4b0
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Showing 2 changed files with 76 additions and 51 deletions.
91 changes: 47 additions & 44 deletions src/com/google/javascript/jscomp/RewriteAsyncFunctions.java
View file
Expand Up @@ -18,7 +18,6 @@
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;

import com.google.common.base.Optional;
import com.google.javascript.jscomp.parsing.parser.FeatureSet;
import com.google.javascript.jscomp.parsing.parser.FeatureSet.Feature;
import com.google.javascript.rhino.IR;
Expand All @@ -27,6 +26,7 @@
import java.util.Deque;
import java.util.LinkedHashSet;
import java.util.Set;
import javax.annotation.Nullable;

/**
* Converts async functions to valid ES6 generator functions code.
Expand Down Expand Up @@ -65,53 +65,59 @@ public final class RewriteAsyncFunctions implements NodeTraversal.Callback, HotS
* for the function currently in context.
*/
private static final class LexicalContext {
final Optional<Node> function; // absent for top level
final LexicalContext thisAndArgumentsContext;
@Nullable final Node function;
@Nullable final LexicalContext asyncThisAndArgumentsContext;
final Set<String> replacedSuperProperties = new LinkedHashSet<>();
boolean mustAddAsyncThisVariable = false;
boolean mustAddAsyncArgumentsVariable = false;

/** Creates root-level context. */
LexicalContext() {
this.function = Optional.absent();
this.thisAndArgumentsContext = this;
function = null;
asyncThisAndArgumentsContext = null;
}

LexicalContext(LexicalContext outer, Node function) {
this.function = Optional.of(function);
// An arrow function shares 'this' and 'arguments' with its outer scope.
this.thisAndArgumentsContext =
function.isArrowFunction() ? outer.thisAndArgumentsContext : this;
this.function = function;

if (function.isAsyncFunction()) {
if (function.isArrowFunction()) {
// An async arrow function context points to outer.asyncThisAndArgumentsContext
// if non-null, otherwise to itself.
asyncThisAndArgumentsContext = outer.asyncThisAndArgumentsContext == null
? this : outer.asyncThisAndArgumentsContext;
} else {
// An async non-arrow function context always points to itself
asyncThisAndArgumentsContext = this;
}
} else {
if (function.isArrowFunction()) {
// A non-async arrow function context always points to outer.asyncThisAndArgumentsContext
asyncThisAndArgumentsContext = outer.asyncThisAndArgumentsContext;
} else {
// A non-async, non-arrow function has no async context.
asyncThisAndArgumentsContext = null;
}
}
}

boolean isAsyncContext() {
return function.isPresent() && function.get().isAsyncFunction();
return function.isAsyncFunction();
}

boolean mustReplaceThisAndArguments() {
return isAsyncContext() || thisAndArgumentsContext.isAsyncContext();
}

LexicalContext getAsyncThisAndArgumentsContext() {
if (thisAndArgumentsContext.isAsyncContext()) {
return thisAndArgumentsContext;
}
// The current context is an async arrow function within a non-async function,
// so it must define its own replacement variables.
checkState(isAsyncContext());
return this;
return asyncThisAndArgumentsContext != null;
}

void recordAsyncThisReplacementWasDone() {
getAsyncThisAndArgumentsContext().mustAddAsyncThisVariable = true;
asyncThisAndArgumentsContext.mustAddAsyncThisVariable = true;
}

void recordAsyncSuperReplacementWasDone(String superFunctionName) {
getAsyncThisAndArgumentsContext().replacedSuperProperties.add(superFunctionName);
asyncThisAndArgumentsContext.replacedSuperProperties.add(superFunctionName);
}

void recordAsyncArgumentsReplacementWasDone() {
getAsyncThisAndArgumentsContext().mustAddAsyncArgumentsVariable = true;
asyncThisAndArgumentsContext.mustAddAsyncArgumentsVariable = true;
}
}

Expand Down Expand Up @@ -143,7 +149,7 @@ public boolean shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent)
if (n.isFunction()) {
contextStack.addFirst(new LexicalContext(contextStack.getFirst(), n));
if (n.isAsyncFunction()) {
compiler.ensureLibraryInjected("es6/execute_async_generator", /* force */ false);
compiler.ensureLibraryInjected("es6/execute_async_generator", /* force= */ false);
}
}
return true;
Expand All @@ -152,17 +158,14 @@ public boolean shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent)
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
LexicalContext context = contextStack.getFirst();

if (n.isFunction()) {
checkState(
context.function.isPresent() && context.function.get() == n,
"unexpected function context:\nexpected: %s\nactual: %s",
n,
context.function);
contextStack.removeFirst();
}
switch (n.getToken()) {
case FUNCTION:
checkState(
context.function == n,
"unexpected function context:\nexpected: %s\nactual: %s",
n,
context.function);
checkState(contextStack.removeFirst() == context);
if (context.isAsyncContext()) {
convertAsyncFunction(context);
}
Expand All @@ -172,15 +175,15 @@ public void visit(NodeTraversal t, Node n, Node parent) {
if (context.mustReplaceThisAndArguments() && n.matchesQualifiedName("arguments")) {
n.setString(ASYNC_ARGUMENTS);
context.recordAsyncArgumentsReplacementWasDone();
compiler.reportChangeToChangeScope(context.function.get());
compiler.reportChangeToChangeScope(context.function);
}
break;

case THIS:
if (context.mustReplaceThisAndArguments()) {
parent.replaceChild(n, IR.name(ASYNC_THIS).useSourceInfoIfMissingFrom(n));
parent.replaceChild(n, IR.name(ASYNC_THIS));
context.recordAsyncThisReplacementWasDone();
compiler.reportChangeToChangeScope(context.function.get());
compiler.reportChangeToChangeScope(context.function);
}
break;

Expand All @@ -198,23 +201,23 @@ public void visit(NodeTraversal t, Node n, Node parent) {
Node getPropReplacement = NodeUtil.newCallNode(IR.name(superPropertyName));
Node grandparent = parent.getParent();
if (grandparent.isCall() && grandparent.getFirstChild() == parent) {
// $super$get$x()(...) => $super$get$x().call($this, ...)
// super.x(...) => super.x.call($this, ...)
getPropReplacement = IR.getprop(getPropReplacement, IR.string("call"));
grandparent.addChildAfter(IR.name(ASYNC_THIS), parent);
grandparent.addChildAfter(IR.name(ASYNC_THIS).useSourceInfoFrom(parent), parent);
context.recordAsyncThisReplacementWasDone();
}
getPropReplacement.useSourceInfoFrom(parent);
getPropReplacement.useSourceInfoFromForTree(parent);
grandparent.replaceChild(parent, getPropReplacement);
context.recordAsyncSuperReplacementWasDone(medhodName.getString());
compiler.reportChangeToChangeScope(context.function.get());
compiler.reportChangeToChangeScope(context.function);
}
break;

case AWAIT:
checkState(context.isAsyncContext(), "await found within non-async function body");
checkState(n.hasOneChild(), "await should have 1 operand, but has %s", n.getChildCount());
// Awaits become yields in the converted async function's inner generator function.
parent.replaceChild(n, IR.yield(n.removeFirstChild()).useSourceInfoIfMissingFrom(n));
parent.replaceChild(n, IR.yield(n.removeFirstChild()));
break;

default:
Expand All @@ -223,7 +226,7 @@ public void visit(NodeTraversal t, Node n, Node parent) {
}

private void convertAsyncFunction(LexicalContext functionContext) {
Node originalFunction = functionContext.function.get();
Node originalFunction = checkNotNull(functionContext.function);
originalFunction.setIsAsyncFunction(false);
Node originalBody = originalFunction.getLastChild();
Node newBody = IR.block().useSourceInfoIfMissingFrom(originalBody);
Expand Down
36 changes: 29 additions & 7 deletions test/com/google/javascript/jscomp/RewriteAsyncFunctionsTest.java
View file
Expand Up @@ -59,9 +59,9 @@ public void testInnerArrowFunctionUsingThis() {
lines(
"class X {",
" m() {",
" const $jscomp$async$this=this;",
" const $jscomp$async$this = this;",
" function* $jscomp$async$generator() {",
" return new Promise((resolve,reject)=>{",
" return new Promise((resolve, reject) => {",
" return $jscomp$async$this",
" });",
" }",
Expand Down Expand Up @@ -91,8 +91,8 @@ public void testInnerSuperCall() {
"}",
"class X extends A {",
" m() {",
" const $jscomp$async$this=this;",
" const $jscomp$async$super$get$m=()=>super.m;",
" const $jscomp$async$this = this;",
" const $jscomp$async$super$get$m = () => super.m;",
" function* $jscomp$async$generator() {",
" return $jscomp$async$super$get$m().call($jscomp$async$this);",
" }",
Expand Down Expand Up @@ -123,7 +123,7 @@ public void testInnerSuperReference() {
"}",
"class X extends A {",
" m() {",
" const $jscomp$async$super$get$m=()=>super.m;",
" const $jscomp$async$super$get$m = () => super.m;",
" function* $jscomp$async$generator() {",
" const tmp = $jscomp$async$super$get$m();",
" return tmp.call(null);",
Expand All @@ -133,6 +133,28 @@ public void testInnerSuperReference() {
"}"));
}

public void testNestedArrowFunctionUsingThis() {
test(
lines(
"class X {",
" m() {",
" return async () => (() => this);",
" }",
"}"),
lines(
"class X {",
" m() {",
" return () => {",
" const $jscomp$async$this = this;",
" function* $jscomp$async$generator() {",
" return () => $jscomp$async$this;",
" }",
" return $jscomp.executeAsyncGenerator($jscomp$async$generator())",
" }",
" }",
"}"));
}

public void testInnerArrowFunctionUsingArguments() {
test(
lines(
Expand All @@ -146,9 +168,9 @@ public void testInnerArrowFunctionUsingArguments() {
lines(
"class X {",
" m() {",
" const $jscomp$async$arguments=arguments;",
" const $jscomp$async$arguments = arguments;",
" function* $jscomp$async$generator() {",
" return new Promise((resolve,reject)=>{",
" return new Promise((resolve,reject) => {",
" return $jscomp$async$arguments",
" });",
" }",
Expand Down

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