aws-lambda-python: does command_hooks even work?

[rbailey-godaddy]

Describe the bug

See https://docs.aws.amazon.com/cdk/api/v2/docs/aws-lambda-python-alpha-readme.html#command-hooks where this example is provided:

const entry = '/path/to/function';
new python.PythonFunction(this, 'function', {
  entry,
  runtime: Runtime.PYTHON_3_8,
  bundling: {
    commandHooks: {
      // run tests
      beforeBundling(inputDir: string): string[] {
        return ['pytest'];
      },
      afterBundling(inputDir: string): string[] {
        return ['pylint'];
      },
      // ...
    },
  },
});

I cannot find any example of equivalent code in python, or any statement by anybody claiming to have successfully defined such hooks.

My VSCode tool tips tell me that in this context:

        lambda_common_py310_layer = lambda_python_alpha.PythonLayerVersion(
            self.stack,
            "lambda-common-py310",
            entry="foo",
            bundling=lambda_python_alpha.BundlingOptions(
                command_hooks=what_goes_here,
            ),
            compatible_runtimes=[lambda_.Runtime.PYTHON_3_10],
        )

I should be providing something of type ICommandHooks, but the constructor of that type does not provide any parameters,

If I attempt to define my own class derived from ICommandHooks and replace the after_bundling() and before_bundling() methods, synthesis fails with:

TypeError: Don't know how to convert object to JSON: <stacks.base_stack.BaseStack.__init__.<locals>.MagicHooks object at 0x7f256efcc690>

Expected Behavior

I expect:

1. The (python) documentation includes a (python) example of correct usage of this parameter
2. It actually works

Current Behavior

Here is the full trace:

$ cdk synthesize cirruscan-base
Traceback (most recent call last):
  File "/home/sbailey/GitHub/CirrusScan/app.py", line 47, in <module>
    base = BaseStack(
           ^^^^^^^^^^
  File "/home/sbailey/GitHub/CirrusScan/stacks/base_stack.py", line 363, in __init__
    lambda_common_py310_layer = lambda_python_alpha.PythonLayerVersion(
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/sbailey/GitHub/CirrusScan/.venv/lib/python3.11/site-packages/jsii/_runtime.py", line 112, in __call__
    inst = super().__call__(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/sbailey/GitHub/CirrusScan/.venv/lib/python3.11/site-packages/aws_cdk/aws_lambda_python_alpha/__init__.py", line 1883, in __init__
    jsii.create(self.__class__, self, [scope, id, props])
  File "/home/sbailey/GitHub/CirrusScan/.venv/lib/python3.11/site-packages/jsii/_kernel/__init__.py", line 334, in create
    response = self.provider.create(
               ^^^^^^^^^^^^^^^^^^^^^
  File "/home/sbailey/GitHub/CirrusScan/.venv/lib/python3.11/site-packages/jsii/_kernel/providers/process.py", line 363, in create
    return self._process.send(request, CreateResponse)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/sbailey/GitHub/CirrusScan/.venv/lib/python3.11/site-packages/jsii/_kernel/providers/process.py", line 322, in send
    data = json.dumps(req_dict, default=jdefault).encode("utf8")
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/json/__init__.py", line 238, in dumps
    **kw).encode(obj)
          ^^^^^^^^^^^
  File "/usr/lib/python3.11/json/encoder.py", line 200, in encode
    chunks = self.iterencode(o, _one_shot=True)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/json/encoder.py", line 258, in iterencode
    return _iterencode(o, 0)
           ^^^^^^^^^^^^^^^^^
  File "/home/sbailey/GitHub/CirrusScan/.venv/lib/python3.11/site-packages/jsii/_kernel/providers/process.py", line 149, in jdefault
    raise TypeError("Don't know how to convert object to JSON: %r" % obj)
TypeError: Don't know how to convert object to JSON: <stacks.base_stack.BaseStack.__init__.<locals>.MagicHooks object at 0x7f256efcc690>

Subprocess exited with error 1

The MagicHooks object is an instance of my derived class (see below)

Reproduction Steps

        class MagicHooks(lambda_python_alpha.ICommandHooks):
            def after_bundling(self, input_dir, output_dir):
                return []

            def before_bundling(self, input_dir, output_dir):
                return [
                    (
                        "poetry export -f requirements.txt --output requirements.txt"
                        " --without-hashes --only=common && "
                        "rm pyproject.toml poetry.lock"
                    )
                ]

        lambda_common_py310_layer = lambda_python_alpha.PythonLayerVersion(
            self.stack,
            "lambda-common-py310",
            entry="common",  # so common is a subdirectory,
            bundling=lambda_python_alpha.BundlingOptions(
                # We only want some of the dependencies; do the generation ourselves
                # so resolver knows what to do. See this reference:
                # https://pypi.org/project/aws-cdk.aws-lambda-python-alpha/
                command_hooks=MagicHooks(),
            ),
            compatible_runtimes=[lambda_.Runtime.PYTHON_3_10],
        )

Possible Solution

I suspect this is a documentation problem, but I am TypeScript-illiterate and at a loss regarding how to restate the given TypeScript example in native python.

Additional Information/Context

No response

CDK CLI Version

2.72.1 (build ddbfac7)

Framework Version

No response

Node.js Version

I don't know how to figure this out

OS

Debian Linux 12.0

Language

Python

Language Version

3.11.2 targeting 3.10

Other information

See #23330 where I believe this support was introduced.

[rbailey-godaddy]

I am still fumbling through this, but it appears the solution is that the interface guidance at https://docs.aws.amazon.com/cdk/v2/guide/work-with-cdk-python.html must be followed, and defining my MagicHooks this way:

        @jsii.implements(lambda_python_alpha.ICommandHooks)
        class MagicHooks:
            def after_bundling(self, input_dir: str, output_dir: str) -> List[str]:
                return []

            def before_bundling(self, input_dir: str, output_dir: str) -> List[str]:
                return [
                    (
                        "poetry export -f requirements.txt --output requirements.txt"
                        " --without-hashes --only=common"
                    )
                ]

Will synthesize successfully. At least after I fix my other logic errors that result in the generated script failing LOL...

[pahud]

Yeah thank you for pointing it out 👍

[rbailey-godaddy]

I successfully coerced my build into working and this indeed was the key step.

[peterwoodworth]

Seems like a documentation issue then?

[github-actions]

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[bestickley]

This issue should be re-opened and the docs fixed. The docs here show invalid Python code :/