Lambda.Function.lambda_from_arn doesn't work like a Lambda

[noesnaterse]

Describe the bug

Lambda.Function.function_from_arn doesn't produce a Lambda function

Expected Behavior

I expected to call any methods I call on a Lambda function from ARN as I can do on a real Lambda

Current Behavior

This works

my_lambda = lambda_.Function(
    self,
    "my_lambda",
    function_name="my_lambda",
    description="A Lambda to test permissions",
    code=lambda_code,
    memory_size=512,
    handler="my_lambda.main",
    runtime=lambda_.Runtime.PYTHON_3_9,
    architecture=lambda_.Architecture.ARM_64,
    timeout=Duration.minutes(1),
)


table = dynamodb.Table(
    self,
    'test_table',
    partition_key=dynamodb.Attribute(
        name="id",
        type=dynamodb.AttributeType.STRING,
    ),
)
table.grant_full_access(my_lambda)

Reproduction Steps

This doesn't work

my_lambda = lambda_.Function(
    self,
    "my_lambda",
    function_name="my_lambda",
    description="A Lambda to test permissions",
    code=lambda_code,
    memory_size=512,
    handler="my_lambda.main",
    runtime=lambda_.Runtime.PYTHON_3_9,
    architecture=lambda_.Architecture.ARM_64,
    timeout=Duration.minutes(1),
)


table = dynamodb.Table(
    self,
    'test_table',
    partition_key=dynamodb.Attribute(
        name="id",
        type=dynamodb.AttributeType.STRING,
    ),
)

s3_by_arn = lambda_.Function.from_function_arn(
            self,
            "s3object_lambda_appsync_by_proxy",
            s3object_lambda.function_arn
        )
table.grant_full_access(s3_by_arn)

Possible Solution

For me it would help if the reproducion steps would work exactly like the current_behavior step.
A Lambda should work like a Lambda no matter how you obtain it.

Additional Information/Context

I have two different stacks in which I define the Lambda and one in which I define the DynamoDB table, so that is why I use the function_from_arn method to get the Lambda and give it access rights.

CDK CLI Version

2.54.0 (build 9f41881)

Framework Version

V2

Node.js Version

v14.20.0

OS

Linux

Language

Python

Language Version

Python 3.9.13

Other information

No response

[peterwoodworth]

This is because the role associated with the Lambda that this function needs to add permissions to is not defined. You can import and associate this role to the lambda function with fromFunctionAttributes()

I expected to call any methods I call on a Lambda function from ARN as I can do on a real Lambda

This won't necessarily be true for any given construct that is imported. See here for more info. Ping me if you have any followup questions, thanks!

[github-actions]

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