Build fails with "Object of type PosixPath is not JSON serializable"

[michaelweinold]

Description

When adding our bw2io package to the environment.yaml as a dependency, I get an error of this kind:

TypeError: Object of type PosixPath is not JSON serializable

Interestingly, the error does not reference the package, nor any of its dependencies. The error trace goes from the micromamba build library to jupyterlite_core/manager > jupyterlite_xeus/add_on > empack/pack and then to the Pyhon JSON decoder.

Any idea what the cause might be?

Reproduce

1. Run build workflow at michaelweinold/jl_xeus_test

Expected behavior

No error 😇

Context

• JupyterLite version: jupyterlite-core=0.3.0, jupyterlite-xeus=0.1.9
• Operating System and version: N/A
• Browser and version: N/A

Build Log

Transaction finished
To activate this environment, use:
micromamba activate xeus-python-kernel

Or to execute a single command in this environment, use:
micromamba run -n xeus-python-kernel mycommand

[LiteBuildApp] ERROR | [lite] [post_build] [jupyterlite-xeus] [ERR] Object of type PosixPath is not JSON serializable
Traceback (most recent call last):
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/doit_cmd.py", line 294, in run
return command.parse_execute(args)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/cmd_base.py", line 150, in parse_execute
return self.execute(params, args)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/cmd_base.py", line 570, in execute
return self._execute(**exec_params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/cmd_run.py", line 265, in _execute
return runner.run_all(self.control.task_dispatcher())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/runner.py", line 254, in run_all
self.run_tasks(task_dispatcher)
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/runner.py", line 213, in run_tasks
node = task_dispatcher.generator.send(node)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/control.py", line 629, in _dispatcher_generator
next_step = node.step()
^^^^^^^^^^^
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/control.py", line 336, in step
return next(self.generator)
^^^^^^^^^^^^^^^^^^^^
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/control.py", line 345, in _func
for value in decorated(*args, **kwargs):
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/control.py", line 473, in _add_task
new_tasks = generate_tasks(to_load, task_gen, ref.doc)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/loader.py", line 390, in generate_tasks
for task_dict, x_doc in flat_generator(gen_result, gen_doc):
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/doit/loader.py", line 27, in flat_generator
for item in gen:
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/jupyterlite_core/manager.py", line 138, in _delayed_gather
yield from _gather()
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/jupyterlite_core/manager.py", line 131, in _gather
raise error
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/jupyterlite_core/manager.py", line 123, in _gather
for task in getattr(addon, attr)(self):
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/jupyterlite_xeus/add_on.py", line 127, in post_build
yield from self.copy_kernels_from_prefix()
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/jupyterlite_xeus/add_on.py", line 179, in copy_kernels_from_prefix
yield from self.copy_kernel(kernel_dir, kernel_wasm, kernel_js)
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/jupyterlite_xeus/add_on.py", line 261, in copy_kernel
yield from self.pack_prefix(kernel_dir=kernel_dir)
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/jupyterlite_xeus/add_on.py", line 288, in pack_prefix
pack_env(
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/empack/pack.py", line 186, in pack_env
pack_pkg_impl(
File "/home/runner/micromamba/envs/build-env/lib/python3.11/site-packages/empack/pack.py", line 54, in pack_pkg_impl
json.dump(pkg_meta, f)
File "/home/runner/micromamba/envs/build-env/lib/python3.11/json/init.py", line 179, in dump
for chunk in iterable:
File "/home/runner/micromamba/envs/build-env/lib/python3.11/json/encoder.py", line 432, in _iterencode
yield from _iterencode_dict(o, _current_indent_level)
File "/home/runner/micromamba/envs/build-env/lib/python3.11/json/encoder.py", line 406, in _iterencode_dict
yield from chunks
File "/home/runner/micromamba/envs/build-env/lib/python3.11/json/encoder.py", line 326, in _iterencode_list
yield from chunks
File "/home/runner/micromamba/envs/build-env/lib/python3.11/json/encoder.py", line 439, in _iterencode
o = _default(o)
^^^^^^^^^^^
File "/home/runner/micromamba/envs/build-env/lib/python3.11/json/encoder.py", line 180, in default
raise TypeError(f'Object of type {o.class.name} '
TypeError: Object of type PosixPath is not JSON serializable