Avoid executing the code in the All Fetch Listeners Are Empty algorithm.

[yoshisatoyanagisawa]

This is for stop calling Get for detecting an empty fetch listener. Benefit of the change is that it won't execute the Javascript, and drawback is that it just ignores an empty fetch listener defined as a handleEvent property. Since it is rare to configure the fetch event listener with the handleEvent property, not detecting empty function body for it should be negligible coverage reduction.

+@domenic

---

Preview | Diff

[jakearchibald]

This looks good, but can you add a note that makes it clear that we're deliberately returning false for handleEvent?

[jakearchibald]

@annevk @youennf @asutherland This is a change to the "optimise for empty fetch listeners" feature (#1671).

Previously, we were looking at both regular listeners, and { handleEvent } listeners. However, running getters during the check adds a bunch of complexity. With this change, the optimisation doesn't apply if there's a non-callable listener object (as in, { handleEvent }).

[yoshisatoyanagisawa]

This looks good, but can you add a note that makes it clear that we're deliberately returning false for handleEvent?

Sure. I have added the note.
I am not confident that the explanation makes sense to you.

[yoshisatoyanagisawa]

Hi, are there any updates on this?
This narrows down the area, which is treated as an empty fetch handler to exclude something rarely used for the PWA purpose.

[jakearchibald]

LGTM