#18195 Include appropriate `complete_platforms` for serverless environments `runtime` Issue created by huonw Is your feature request related to a problem? Please describe. Currently building Serverless artefacts like AWS Lambda or GCF supports both a quick-and-easy

runtime

setting, and a

complete_platforms

. Generally setting

complete_platforms

is required to get the right wheels, and setting

runtime

is not useful/misleading/causes problems (e.g. #15296, #18001, and a continual stream of questions in Slack). Describe the solution you'd like I think the environments for a given runtime are generally pretty stable, so pants itself could potentially include an appropriate complete platform JSON for each

runtime

setting (so 3 for AWS Lambda, and 4 for GCF). That is, something like

python_awslambda(..., runtime="python39")

would be translated into calling pex with a pants-provided complete platform JSON, rather than just a simple platform identifier. Having pants provide a complete platform almost certainly won't be worse than not using a complete platform at all, and would hopefully mean fewer users have problems. Any users who still have problems can provide their own complete platform. Downside: if the complete platform pants provides is changed (e.g. pants 2.35 has a new JSON than pants 2.34), built artefacts may change after a user upgrades to 2.35, due to differing wheel selection. Describe alternatives you've considered Just not doing this, because the downsides/risks are too large? Additional context The complete platforms can be generated by running PEX in each of the relevant environments. For instance, we're deploying AWS Lambdas using a complete platform generated by:

import subprocess

def lambda_handler(event, context):
    subprocess.run(
        """
        pip install --target=/tmp/subdir pex
        PYTHONPATH=/tmp/subdir /tmp/subdir/bin/pex3 interpreter inspect --markers --tags
        """,
        shell=True
    )
    return {
        'statusCode': 200,
        'body': "{}",
    }

I think this would "just" mean switching the following bit of code to select an appropriate pants-provided JSON file, rather than just constructing the platform string: pants/src/python/pants/backend/awslambda/python/rules.py Lines 101 to 114 in </pantsbuild/pants/commit/4b2bc114aafe05a1abdb81ab92d31cd275a7012d|4b2bc11> pantsbuild/pants