JsExecuteContext memory leak

[rpaquay]

Every time we run a command in wash (e.g. echo foo), we leak 2 instances of JsExecuteContext.

It seems the culprit is the call to dependsOn in the ExecuteContext contructor:

export var ExecuteContext = function(fileSystem, stdio, path, args) {
  Ephemeral.call(this);

  (...)
  // If the parent file system is closed, we close too.
  this.dependsOn(this.fileSystem);
  (...)
};

And the dependsOn function:

Ephemeral.prototype.dependsOn = function(otherEphemeral) {
  otherEphemeral.onClose.addListener(
    function() {
      if (this.isEphemeral('Closed', 'Error'))
        return;

      this.closeError(new AxiomError.ParentClosed(otherEphemeral.closeReason,
                                                  otherEphemeral.closeValue));
    }.bind(this));
};

What happens in this case:

• otherEphemeral is the jsfs file system instance, which lives much longer that the execute context
• this is the execute context, and it is captured by a closure added to otherEphemeral
• Hence, the execute context will live as long as the file system lives.

While this is technically not a memory leak, the effect for wash is that we keep alive all instances of execute context we create, because the file system instance is never released.