fix(metrics): lambda_handler typing, and **kwargs preservation all middlewares

[heitorlessa]

Issue number: #3447

Summary

This PR allows @metrics.log_metrics decorator to support custom Lambda Handlers that are either extended with dependency injection, or Event type overridden.

Changes

Please provide a summary of what's being changed

User experience

Please share what the user experience looks like before and after this change

The following Lambda handler signature now passes Pylance checks, and extra keyword arguments are preserved when stacking decorators.

import json
from typing import List

from aws_lambda_powertools import Logger, Metrics
from aws_lambda_powertools.utilities.parser import BaseModel, Field, event_parser
from aws_lambda_powertools.utilities.typing import LambdaContext


logger = Logger()
metrics = Metrics()


class AgentQuery(BaseModel):
    username: str
    user_query: str


@logger.inject_lambda_context
@metrics.log_metrics(capture_cold_start_metric=True)
@event_parser(model=AgentQuery)
def lambda_handler(event: AgentQuery, context: LambdaContext, my_dependency = None):
    logger.info("hi")

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• Meet tenets criteria
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented
• PR title follows conventional commit semantics

Is this a breaking change?

RFC issue number:

Checklist:

• Migration process documented
• Implement warnings (if it can live side by side)

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.43%. Comparing base (05dd82b) to head (00eaffc).
⚠️ Report is 2707 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3460   +/-   ##
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  Coverage    95.42%   95.43%           
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  Files          209      209           
  Lines         9664     9675   +11     
  Branches      1773     1774    +1     
========================================
+ Hits          9222     9233   +11     
  Misses         329      329           
  Partials       113      113           

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[heitorlessa]

wait, event_parser also doesn't preserve kwargs..... 🤦🏻

[heitorlessa]

Found the same issue in the Middleware Factory, subsequently having the same issue in Validation, Idempotency, and Parser.

Fixed in all of them. Besides make pr, created the following dummy script to test all of them:

---

from aws_lambda_powertools import Logger, Metrics
from aws_lambda_powertools.utilities.parser import BaseModel, event_parser
from aws_lambda_powertools.utilities.typing import LambdaContext
from aws_lambda_powertools.utilities.validation import validator
from aws_lambda_powertools.utilities.idempotency import idempotent_function, idempotent
from aws_lambda_powertools.utilities.idempotency.persistence.dynamodb import DynamoDBPersistenceLayer
from dataclasses import dataclass

logger = Logger()
metrics = Metrics(namespace="test")
persistence = DynamoDBPersistenceLayer(table_name="idem")

SCHEMA = {
    "$schema": "http://json-schema.org/draft-07/schema",
    "$id": "http://example.com/example.json",
    "type": "object",
    "title": "Sample schema",
    "description": "The root schema comprises the entire JSON document.",
    "required": ["username", "user_query"],
    "properties": {
        "username": {
            "$id": "#/properties/username",
            "type": "string",
            "title": "The username",
            "maxLength": 50,
        },
        "user_query": {
            "$id": "#/properties/user_query",
            "type": "string",
            "title": "The user_query",
            "maxLength": 30,
        },
    },
}


class AgentQuery(BaseModel):
    username: str
    user_query: str


@idempotent_function(data_keyword_argument="my_dependency", persistence_store=persistence)
def use_dependency(my_dependency):
    return my_dependency


@validator(inbound_schema=SCHEMA)
@event_parser(model=AgentQuery)
@logger.inject_lambda_context
@metrics.log_metrics(capture_cold_start_metric=True)
@idempotent(persistence_store=persistence)
def lambda_handler(event: AgentQuery, context: LambdaContext, my_dependency: str | None = None) -> None:
    use_dependency(my_dependency=my_dependency)
    logger.info("hi", my_dependency=my_dependency)


@dataclass
class DummyLambdaContext:
    function_name: str = "test"
    memory_limit_in_mb: int = 128
    invoked_function_arn: str = "arn:aws:lambda:eu-west-1:809313241:function:test"
    aws_request_id: str = "52fdfc07-2182-154f-163f-5f0f9a621d72"

    def get_remaining_time_in_millis(self):
        return 10 * 1000


event = AgentQuery(username="lessa", user_query="kaodsk").dict()

lambda_handler(event, DummyLambdaContext(), my_dependency="test")

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3.1% Duplication

[leandrodamascena]

APPROVED! 🚀