Develop Lib and App in parallel - how to update automatically

Libraries
2

I continued checking for a solution.

I found this older post Library Development HowTo

I have now the following files:

platformio.ini

[platformio]
description = PIO Example
[common]
includes = -IFooLib
cpu_flags =  -Os -g  --specs=nosys.specs -flto -ffreestanding -nostdlib -L. -T./flash.lds -Xlinker 
defines = -DFW_VERSION=v0.0.1

[env:MyBoard]
platform = atmelsam
board = MyBoard
build_flags = ${common.cpu_flags} ${common.includes} ${common.defines} 
#lib_deps = file://./FooLib
lib_extra_dirs = ./FooLib

FooLib\library.json

{
  "name": "FooLib",
  "keywords": "foo fooFast",
  "description": "fullblown FOO implementation without BAR",
  "version" : "0.0.1",
  "platforms": "atmelsam",
  "build": {
    "flags" : ["-DLIB_WITH_FOO_A"]
  }  
}

With just lib_extra_dirs it use modified files from ./FooLib/src but it ignores the “-D-values” set in library.json.

If lib_deps = file://./FooLib is enabled, it copies the sources into .piolibdeps once but ignores any further updates in FooLib/src

What can I do, that values in FooLib/library.json are used without lib_deps?