Change Log emitters to not emit event when block output is nil

[robacarp]

fixes #11997

[straight-shoota]

Could you please add a note about this to the API docs?

[straight-shoota]

Happy to see your first PR here, btw. 😄

[robacarp]

@straight-shoota Good call. I added an example here as well. The documentation here felt like it could be improved a bit by restructuring this macro iteration in order to get the name of the severity instead of just the number:

Before:

After:

I didn't want to get too far into the weeds, I'm not sure if these out of scope changes are welcome in this pull request.

[Blacksmoke16]

do / end would fit better. Multiline using { }, while valid, is more so used for single line blocks. E.g. Log.warn { "Nothing will be logged" if false } versus:

Log.warn do
  if false
    "Nothing will be logged"
  end
end

[straight-shoota]

It's a stylistic debate. { } is perfectly fine. It's often used to indicate that the block's output value matters.

[robacarp]

I switched this from:

"[methods] can be used" to "use the [methods]" which feels like it is more consistent with the technical writing tone I've observed elsewhere in the docs.

[straight-shoota]

👍