Packages without dependencies

[functorism]

For packages without dependencies pnpm does not create a shrinkwrap.yaml file. This is not considered in the current code - and it therefore crashes on packages without dependencies.

I tried to amend this by exporting an identity object of the "internal" shrinkwrap structure. The code doing the import could then check if the file exists and either import the file (and send it over to rewriteShrinkWrap) or return the identity object. But this does not work in all situations. It breaks on one of the existing tests actually (file-dependencies) - because one can not use builtins.pathExists on paths belonging to other derivations (if I'm getting that right...).

The faulty solution I tried can be found here - together with a test that illustrates the problem.

https://github.com/functorism/pnpm2nix/commit/2946edc19ed1974e1de7940de2843a8e4f78f561