[Discuss-gnuradio] GRC: management of default global_blocks_path triggers silent failure

[Emmanuel Blot]

When upgrading from RC2 to final, a new issue arose:

$ gnuradio-companion
Traceback (most recent call last):
  File "gnuradio/3.8.0.0/libexec/bin/gnuradio-companion", line 102, in 
<module>
    run_main()
  File "gnuradio/3.8.0.0/libexec/bin/gnuradio-companion", line 95, in 
run_main
    exit(main())
  File 
"gnuradio/3.8.0.0/lib/python3.7/dist-packages/gnuradio/grc/main.py", 
line 83, in main
    platform.build_library()
  File 
"gnuradio/3.8.0.0/lib/python3.7/dist-packages/gnuradio/grc/core/platform.py", 
line 197, in build_library
    utils.hide_bokeh_gui_options_if_not_installed(self.blocks['options'])
  File 
"python/3.7.4/Frameworks/Python.framework/Versions/3.7/lib/python3.7/collections/__init__.py", 
line 916, in __getitem__
    return self.__missing__(key)            # support subclasses that 
define __missing__
  File 
"python/3.7.4/Frameworks/Python.framework/Versions/3.7/lib/python3.7/collections/__init__.py", 
line 908, in __missing__
    raise KeyError(key)
KeyError: 'options'

However, deleting the ~/.gnuradio folder makes this issue disappeared.

It seems the issue comes from the global_blocks_path key from 
~/.gnuradio/config.conf.

As my installation path has changed (from .../3.8.0.0-rc2/... to 
.../3.8.0.0/...), the global_blocks_path - which had been 
*automatically* stored by the previous installation of gnuradio - is 
kept being used and silently makes the new installation of gnuradio to 
fail.

I’m not sure what would be the best fix here:
 * always consider the default global_blocks_path as a fallback if no 
valid path is found in `block_paths` property,
 * or fail with an explicit error if no valid path is found, or/and
 * do not automatically define the default global_blocks_path into the 
user configuration file.

Either way, returning an empty list as `Config.block_paths` propagates 
an error into the callstack of GRC to a point it is quite hard to 
understand the root error cause.

Environment:

os: macOS 10.14.6
python: 3.7.3
gtk: 3.24.10 (Quartz backend)
gobject-introspection: 1.60.2
pygobject3: 3.32.2
cairo: 1.16.0
pango: 1.44.3
glib: 2.60.6

HTH,
Emmanuel.