Installation fails due to conflicting pyyaml version

[NeolithEra]

Hi, users are unable to run ssmash due to dependency conflict with pyyaml package. As shown in the following full dependency graph of ssmash, ssmash requires pyyaml >=5.1,<6，while flying-circus requires <5.2.0,>=5.1.1.

According to pip’s “first found wins” installation strategy, pyyaml 5.2 is the actually installed version. However, pyyaml 5.2 does not satisfy PyYAML<5.2.0,>=5.1.1.

Dependency tree-----------

ssmash - 2.0.1
| +- click(install version:7.0 version range:>=7.0,<8)
| +- flying-circus(install version:0.7.2 version range:>=0.7,<0.8)
| | +- attrs(install version:19.3.0 version range:>=18.2.0)
| | +- inflection(install version:0.3.1 version range:<0.4,>=0.3.1)
| | +- pyyaml(install version:3.13 version range:<5.2.0,>=5.1.1)
| +- inflection(install version:0.3.1 version range:==0.3.1)
| +- pyyaml(install version:5.2 version range:>=5.1,<6)

Thanks for your help.
Best,
Neolith

[NeolithEra]

Suggested Solution

1. Fix your direct dependency to be pyyaml <5.2.0. I have checked this revision will not affect your downstream projects now.

2. Remove your direct dependency pyyaml, and use pyyaml transitively introduced by flying-circus.

3. Ask your upstream project flying-circus to loose the version range of pyyaml.

@garyd203 Which solution do you prefer, 1, 2 or 3?
Please let me know your choice. I can submit a PR to solve this issue.

[garyd203]

Hi @NeolithEra , thanks a lot for the detailed bug report. This issue hadn't affected me because I have been using poetry to install (which does resolve the PyYAML versions in a compatible way), rather than pip, so thanks for bringing it to my attention.

For a solution, it's not desirable to loosen the PyYAML version range for flying-circus (which is somewhat coupled to the internals of PyYAML), unfortunately.

The best approach seems to be if we restrict our version of PyYAML to something compatible (say, "PyYAML>=5.1,<5.2") - your option (1). Are you happy to put together a PR along those lines?

[garyd203]

I will pick this up

[garyd203]

Appears to be resolved now. Thanks @NeolithEra :)

$ docker run -it python:3.6 "bash"
root:/# pip install ssmash
/ ... /
Installing collected packages: click, inflection, PyYAML, attrs, flying-circus,
ssmash
Successfully installed PyYAML-5.1.2 attrs-18.2.0 click-7.0 flying-circus-0.7.2 i
nflection-0.3.1 ssmash-2.1.2

root:/# ssmash --help
Usage: ssmash [OPTIONS] COMMAND1 [ARGS]... [COMMAND2 [ARGS]...]...

  Convert a plain YAML file with application configuration into a
  CloudFormation template with SSM parameters.

Options:
  -i, --input, --input-file FILENAME
                                  Where to read the application configuration
                                  YAML file
  -o, --output, --output-file FILENAME
                                  Where to write the CloudFormation template
                                  file
  --description TEXT              The description for the CloudFormation
                                  stack.
  --help                          Show this message and exit.

Commands:
  invalidate-ecs     Invalidate the cache in an ECS Service that uses these...
  invalidate-lambda  Invalidate the cache in a Lambda Function that uses...