Package com.google.javascript.jscomp

Class RewriteAsyncFunctions

java.lang.Object

com.google.javascript.jscomp.RewriteAsyncFunctions

All Implemented Interfaces:

CompilerPass, NodeTraversal.Callback

public final class RewriteAsyncFunctions
extends java.lang.Object
implements NodeTraversal.Callback, CompilerPass

Converts async functions to valid ES6 generator functions code.

This pass must run before the passes that transpile let declarations, arrow functions, and generators.

An async function, foo(a, b), will be rewritten as:

 function foo(a, b) {
   let $jscomp$async$this = this;
   let $jscomp$async$arguments = arguments;
   let $jscomp$async$super$get$x = () => super.x;
   return $jscomp.asyncExecutePromiseGeneratorFunction(
       function* () {
         // original body of foo() with:
         // - await (x) replaced with yield (x)
         // - arguments replaced with $jscomp$async$arguments
         // - this replaced with $jscomp$async$this
         // - super.x replaced with $jscomp$async$super$get$x()
         // - super.x(5) replaced with $jscomp$async$super$get$x().call($jscomp$async$this, 5)
       });
 }
 

Method Summary

Modifier and Type	Method	Description
void	process(Node externs, Node root)	Process the JS with root node root.
boolean	shouldTraverse(NodeTraversal nodeTraversal, Node n, Node parent)	Visits a node in preorder (before its children) and decides whether the node and its children should be traversed.
void	visit(NodeTraversal t, Node n, Node parent)	Visits a node in postorder (after its children).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

process

public void process(Node externs,
                    Node root)

Description copied from interface: CompilerPass

Process the JS with root node root. Can modify the contents of each Node tree

Specified by:

process in interface CompilerPass

Parameters:

externs - Top of external JS tree

root - Top of JS tree

shouldTraverse

public boolean shouldTraverse(NodeTraversal nodeTraversal,
                              Node n,
                              Node parent)

Description copied from interface: NodeTraversal.Callback

Visits a node in preorder (before its children) and decides whether the node and its children should be traversed.

If this method returns true, the node will be visited by NodeTraversal.Callback.visit(NodeTraversal, Node, Node) in postorder and its children will be visited by both NodeTraversal.Callback.shouldTraverse(NodeTraversal, Node, Node) in preorder and by NodeTraversal.Callback.visit(NodeTraversal, Node, Node) in postorder.

If this method returns false, the node will not be visited by NodeTraversal.Callback.visit(NodeTraversal, Node, Node) and its children will neither be visited by NodeTraversal.Callback.shouldTraverse(NodeTraversal, Node, Node) nor NodeTraversal.Callback.visit(NodeTraversal, Node, Node).

Siblings are always visited left-to-right.

Implementations can have side-effects (e.g. modify the parse tree). Removing the current node is legal, but removing or reordering nodes above the current node may cause nodes to be visited twice or not at all.

Specified by:

shouldTraverse in interface NodeTraversal.Callback

Parameters:

nodeTraversal - The current traversal.

n - The current node.

parent - The parent of the current node.

Returns:

whether the children of this node should be visited

visit

public void visit(NodeTraversal t,
                  Node n,
                  Node parent)

Description copied from interface: NodeTraversal.Callback

Visits a node in postorder (after its children). A node is visited in postorder iff NodeTraversal.Callback.shouldTraverse(NodeTraversal, Node, Node) returned true for its parent and itself. In particular, the root node is never visited in postorder.

Siblings are always visited left-to-right.

Implementations can have side-effects (e.g. modify the parse tree). Removing the current node is legal, but removing or reordering nodes above the current node may cause nodes to be visited twice or not at all.

Specified by:

visit in interface NodeTraversal.Callback

Parameters:

t - The current traversal.

n - The current node.

parent - The parent of the current node.