Add support for Lambda Layers in lambda.Function construct

[spg]

As of now, adding layers to a lambda function requires jumping through a few hoops:

const entrypoint = new lambda.Function(this, 'MyFunc', {
    runtime: new Runtime("python3.7"),
    code: lambda.Code.asset("my_custom_python_func"),
    handler: "hello.my_handler"
});

const asset = new assets.ZipDirectoryAsset(this, 'SampleAsset', {
    path: path.join(__dirname, '../layers/my-layer')
});

const layer = new cdk.Resource(this, 'MyLayer', {
    type: 'AWS::Lambda::LayerVersion',
    properties: {
        Content: {
            S3Bucket: asset.s3BucketName,
            S3Key: asset.s3ObjectKey,
        }
    }
});

const functionResource = entrypoint.findChild('Resource') as lambda.cloudformation.FunctionResource;
functionResource.propertyOverrides.layers = [layer.ref];

Adding layers support to lambda.FunctionProps would simplify this process.

[eladb]

👍

[madshargreave]

👍

[spg]

Done in #1411

[yoslev]

The python version of cdk layer deployment for those who need:
import typing

from aws_cdk import (
aws_lambda as _lambda,
core,
aws_iam)
from aws_cdk.aws_iam import PolicyStatement
from aws_cdk.aws_lambda import LayerVersion, AssetCode
from aws_cdk.core import Stack

class CdkLayersStack(core.Stack):

def __init__(self, scope: core.Construct, id: str, **kwargs) -> None:
    super().__init__(scope, id, **kwargs)

    # 1) deploy lambda functions
    testLambda : _lambda.Function = CdkLayersStack.cdkResourcesCreate(self)

    # 2) attach policy to function
    projectPolicy = CdkLayersStack.createPolicy(self, testLambda)

# -----------------------------------------------------------------------------------
@staticmethod
def createPolicy(this, testLambda:_lambda.Function) -> None:
    projectPolicy:PolicyStatement = PolicyStatement(
        effect=aws_iam.Effect.ALLOW,
        # resources=["*"],
        resources=[testLambda.function_arn],
        actions=[ "dynamodb:Query",
                  "dynamodb:Scan",
                  "dynamodb:GetItem",
                  "dynamodb:PutItem",
                  "dynamodb:UpdateItem",
                  "states:StartExecution",
                  "states:SendTaskSuccess",
                  "states:SendTaskFailure",
                  "cognito-idp:ListUsers",
                  "ses:SendEmail"
                ]
    )
    return projectPolicy;
# -----------------------------------------------------------------------------------
@staticmethod
def cdkResourcesCreate(self) -> None:
    lambdaFunction:_lambda.Function = _lambda.Function(self, 'testLambda',
                                                       function_name='testLambda',
                                                       handler='testLambda.lambda_handler',
                                                       runtime=_lambda.Runtime.PYTHON_3_7,
                                                       code=_lambda.Code.asset('functions'),
                                                       )
    ac = AssetCode("layers")
    layer  = LayerVersion(self, "l1", code=ac, description="test-layer", layer_version_name='Test-layer-version-name')
    lambdaFunction.add_layers(layer)

    return lambdaFunction
# -----------------------------------------------------------------------------------