feat(apigateway): add exception_handler support

[michaelbrewer]

Issue #, if available:

• https://github.com/awslabs/aws-lambda-powertools-python/issues/899

Description of changes:

app = ApiGatewayResolver()


@app.exception_handler(SomeKindOfError)
def handle_error(ex: SomeKindOfError):
   print(f"request path is '{app.current_event.path}'")
   return Response(
       status_code=418,
       content_type=content_types.TEXT_HTML,
       body=str(ex),
   )


@app.not_found()
def handle_not_found(exc: NotFoundError):
    return Response(status_code=404, content_type=content_types.TEXT_PLAIN, body="I am a teapot!")


@app.exception_handler(ServiceError)
def service_error(ex: ServiceError):
    logger.debug(f"Log out sensitive stuff: {ex.msg}")
    return Response(
        status_code=ex.status_code,
        content_type=content_types.APPLICATION_JSON,
        body="CUSTOM ERROR FORMAT",
    )


@app.get("/my/path")
def call_with_error() -> Response:
   raise SomeKindOfError("Foo!")

Checklist

• Meet tenets criteria
• Update tests
• Update docs
• PR title follows conventional commit semantics

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Merging #898 (eb1d7a8) into develop (e91932c) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop     #898   +/-   ##
========================================
  Coverage    99.88%   99.88%           
========================================
  Files          118      118           
  Lines         5139     5162   +23     
  Branches       573      578    +5     
========================================
+ Hits          5133     5156   +23     
  Misses           2        2           
  Partials         4        4           

Impacted Files	Coverage Δ
aws_lambda_powertools/event_handler/api_gateway.py	100.00% <100.00%> (ø)

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[heitorlessa]

That's looking great, thank you for implementing it that quick.

One major question to better understand the int as GitHub Mobile isn't showing me all the code easily.

[heitorlessa]

Minor ask on testing subclass exceptions. If you can't I can do it tomorrow, as I'll merge this along with others in prep for the release.

[heitorlessa]

Leave with me then, I’ll see if issubclass handles, and then merge - I’ll do it tomorrow

…

On Thu, 16 Dec 2021 at 16:31, Michael Brewer ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In aws_lambda_powertools/event_handler/api_gateway.py <#898 (comment)> : > raise + def not_found(self, func: Callable): + return self.exception_handler(NotFoundError)(func) + + def exception_handler(self, exc_class: Type[Exception]): + def register_exception_handler(func: Callable): + self._exception_handlers[exc_class] = func + + return register_exception_handler + + def _lookup_exception_handler(self, exp_type: Type) -> Optional[Callable]: + # Use "Method Resolution Order" to allow for matching against a base class @heitorlessa <https://github.com/heitorlessa> there is a test test_exception_handler_service_error which registers a ServiceError handler and raises a InternalServerError — Reply to this email directly, view it on GitHub <#898 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAZPQBFDKMJZD6M75SXTUE3URIA6FANCNFSM5KCXX7ZQ> . You are receiving this because you were mentioned.Message ID: ***@***.*** com>

[michaelbrewer]

@heitorlessa - it would have to be a different implementation

    def _lookup_exception_handler(self, exp_type: Type) -> Optional[Callable]:
        for cls in exp_type.__mro__:
            if cls in self._exception_handlers:
                return self._exception_handlers[cls]
        return None

vs

    def _lookup_exception_handler(self, exp_type: Type) -> Optional[Callable]:
        for cls in self._exception_handlers.keys()
            if issubclass(exp_type, cls):
                return self._exception_handlers[cls]
        return None

Also we will be aware that order should either matter OR not:

app = ApiGatewayResolver()


@app.exception_handler(InternalServiceError)
def internal_service_error(ex: InternalServiceError):
    ...


@app.exception_handler(ServiceError)
def generic_service_error(ex: ServiceError):
    ...

[heitorlessa]

I see it now, this would likely happen and order is important (MRO is better).

I'll merge as is and write the docs tomorrow

[michaelbrewer]

I see it now, this would likely happen and order is important (MRO is better).

I'll merge as is and write the docs tomorrow

We could possibly expand on the tests to be sure we have a contract of that the behavior would be.