Investigate using vmBeingRendered === null vs isRendering flag

[Gr8Gatsby]

SOMA#506

Migrated issue

Notes:

In theory, vmBeingRendered should never be null when isRendering is true (and vise-versa).

Questions

• Is there ever a case where isRendering would be false and vmBeingRendered would be true?
• What would be the implications of replacing isRendering statements with vmBeingRendered !== null
• It appears that TypeScript would have an easier time with vmBeingRendered !== null, but is that the case?

They are effectively the same. Maybe we can abstract that into a method that we use everywhere:

function isRendering() {
    return vmBeingRendered !== null;
}

and see if engines can optimize that.

[caridy]

We need a volunteer here that want to try to clean this up.

[ravijayaramappa]

This issue is obsolete now. Things have changed after PR #1551.
The engine now has two flags, one to mark the invocation of render() method and another to mark the invocation of executing the template returned by the render method. In both the cases the vmBeingRendered is set. So vmBeingRendered cannot be used to infer which phase the engine is currently in.