Package com.google.javascript.jscomp

Class RewriteAsyncFunctions

  • All Implemented Interfaces:
    CompilerPass, HotSwapCompilerPass, NodeTraversal.Callback
    public final class RewriteAsyncFunctions
extends java.lang.Object
implements NodeTraversal.Callback, HotSwapCompilerPass
    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

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void hotSwapScript​(Node scriptRoot, Node originalRoot)
      Process the JS with root node root.
      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 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

      • hotSwapScript

        public void hotSwapScript​(Node scriptRoot,
                          Node originalRoot)
        Description copied from interface: HotSwapCompilerPass
        Process the JS with root node root. This is supposed to be significantly faster compared to corresponding full-compiler passes.
        Specified by:
        hotSwapScript in interface HotSwapCompilerPass
        Parameters:
        scriptRoot - Root node corresponding to the file that is modified, should be of type Token.SCRIPT.
        originalRoot - Root node corresponding to the original version of the file that is modified. Should be of type token.SCRIPT.

      • 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. 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.