Close urlConn in StaticFile.fromURL

[lhns]

Previous discussion in #3584

The URLConnection in StaticFile.fromURL is never closed (if the resource is not expired).
This PR reuses the already opened URLConnection to read the response body which in effect causes fs2 to close the URLConnection once the body is fully read.

This PR also wraps urlConn.getInputStream.close() in a Try because it should just be a last attempt to close the resource and should return NotModified in case of errors.

Because of the discussion in #3594 I opened this against series/0.21

[rossabaker]

Thanks, looks good. Optional idea below.

[lhns]

Which idea?

[rossabaker]

Sorry, GitHub ate my comment referenced in the review. It's not a blocker, but just a thought.

[rossabaker]

If we used an old-fashioned try-catch block here, we'd save an allocation for a discarded Try value, and be able to log a warning on any exceptions. Without seeing what's being thrown, it's hard to tell whether they'd be noise or something worth addressing.

In any case, returning the NotModified here is correct and a worthwhile improvement.

[satorg]

From my perspective something like the following snippet would look nicer here:

blocker
  .delay(urlConn.getInputStream.close())
  .handleError(_ => ())
  .as( ... )

Because it shows intent in a clearer way.

I'm mildly concerned about using Try just for swallowing exceptions – it is definitely not what it was designed for (even if it does the job).

[lhns]

Yes this looks indeed much nicer.