How to solve JSONDecodeError when using Poetry in Github Actions?

Question

Issue

I've got a problem using poetry install in my CI/CD pipeline (Github Actions), on any GitHub runner, since I migrated from Python 3.8 to Python 3.10.

Installing dependencies from lock file

Package operations: 79 installs, 0 updates, 0 removals
  • Installing pyparsing (3.0.9)
  
JSONDecodeError
  
Expecting value: line 1 column 1 (char 0)
  at /opt/hostedtoolcache/Python/3.10.0/x64/lib/python3.10/json/decoder.py:355 in raw_decode
      351│         """
      352│         try:
      353│             obj, end = self.scan_once(s, idx)
      354│         except StopIteration as err:
    → 355│             raise JSONDecodeError("Expecting value", s, err.value) from None
      356│         return obj, end
      357│ 
Error: Process completed with exit code 1.

I didn't change any lib configuration in my pyproject.toml file, but as you can see above: Poetry hides most of the StackTrace.

What I tried

• Recreating the poetry.lock file.
• Removing the Poetry cache using rm -r ~/.cache/pypoetry/cache/ (and rm -r ~/.cache/pypoetry/).
• Removing the lib that was returning an error (actually, the issue seems to happen with any lib, so that's the reason why I understand it's probably related to poetry and python)

Question

Any idea how to resolve this issue in my CI/CD pipeline?

Answer 1

After a few researches, I found this thread on the poetry GitHub repository from november 2021.

There is this workaround from hoefling GitHub user:

Disabling poetry's experimental new installer may be a workaround for now:

Solution

poetry config experimental.new-installer false

Adding this line in the shell before running the poetry install command resolved my problem!

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Note that in the same thread, another comment from ddc67cd stated that:

the issue is resolved with the new version of cachecontrol==0.12.9 (it should be installed automatically).

But running pip install -U cachecontrol didn't resolve the issue in my specific case (might be worth testing otherwise?).

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It also seems the problem came back recently (July 2022) and this comment suggested a possible root cause to the issue related to the setuptools library.

Anyway, disabling poetry's experimental new installer should resolve the problem for now, until a permanent solution is found.