Symbols not being rendered in empty style

[tobrun]

release-java

master

Issue can be reproduced with the Simple Map Activity using the following commit: 48abc96

cc @tmpsantos @pozdnyakov @alexshalamov

[pozdnyakov]

The issue was introduced with 103f86c
cc @LukasPaczos

[LukasPaczos]

I took this for a spin:

• calling Style::Impl::loadJSON with an empty style string fails
• calling Style::Impl::loadURL with an empty style asset works

Both methods deliver an identical string to Style::Impl::parse. This can be reproduced by commenting/uncommenting this line in db3b980.

Is this an underlying core issue, or is there a reason for this behavior @pozdnyakov? We can change the implementation to use the asset (and the file source request) instead of parsing the style right away, but I'd like to understand why.

[tmpsantos]

Accordingly to the style spec, this is the minimum valid style:

{
  "version": 8,
  "sources": {}, 
  "layers": []
}

[LukasPaczos]

This is what an example from #14751 (comment) uses, which leads me to believe that Style::Impl::loadJSON is not kicking off the right gears internally.