Disable snap-specific modified PYTHONPATH #176
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Summary
Fix Python path search order so that user Python packages have precedence over system Pyton Packages. Enable FreeCAD to use upgraded packages even if an older version is already provided by the system.
Fixes #167
Details
The Python modules search path in FreeCAD is put together on
src/App/FreeCADInit.py. There, initially the path (as insys.path) is set to the standard Python locations adapted to the snap environment:Afterwards, the path for each FreeCAD module is prepended to
sys.path:Peculiarities:
FreeCADInit.pyfile is converted to a C++ header (FreeCADInit.h) at build time, which is included insrc/App/Application.cppThe snap has a mechanism for injecting initialization Python code by adding it to the
SnapSetup/Init.pyfile. As that file is installed on theModdirectory, it will be loaded byFreeCADInit.pyas any other regular module.One of the things that SnapSetup/Init.py does is to initialize the snap-specific
PYTHONPATH. There are two issues with this:PYTHONPATHwas already initialized. Probably somewhere beforeFreeCADInit.pywas executed.SNAP_PYTHONPATHlist in reverse order intosys.pathPoint 2 is the actual issue. Since it reverses the original search path and it appears before it in
sys.path(point 1), it effectively changes the search order. The search order becomes: system paths first (/snap/freecad/1313/usr/local/lib/python3.10/dist-packages) then user paths ($HOME/snap/freecad/common/.local/lib/python3.10/site-packages).This means that the user can install a newer version of a package via
pip, yet that newer version will not be used if there is an older version of the package installed in a system location (e.g. a dependency shipped by FreeCAD, such asifcopenshell). Python will never see the newer version, as it will search the system location, find the package and load it from there.There seems to have been much care put in setting this up in
snapcraft.yaml. So I'm not sure it's an oversight (a bug), or something that used to work in the past and it no longer does. The reverse insertion order at least seems deliberate.As such, I'd rather not remove the code, but just uncomment it for now, with a reference to this PR for more info. In case it turns out that deactivating it is causing issues.
In summary, this PR deactivates setting the snap-specific
PYTHONPATHon startup, as there is no need to modify the already correctPYTHONPATHbeing set before.