(lambda): Add domain helper prop to FunctionUrl

[diesal11]

Describe the feature

The lambda.FunctionUrl construct currently returns the Function URL as a full URL including the scheme + trailing /.

https://*******.lambda-url.ap-southeast-2.on.aws/

In many cases, it's preferable to have just the domain name.

*******.lambda-url.ap-southeast-2.on.aws

Use Case

When serving a Function URL through a Cloudfront Distribution. The following workaround is required to remove the URL Scheme and path from fn_url.url so it can be consumed by Cloudfront.HttpOrigin

fn_url = function.add_function_url(
    auth_type=lmbda.FunctionUrlAuthType.NONE,
)

# This removes the URL Scheme and trailing `/` from the Function URL`
# leaving: "*******.lambda-url.ap-southeast-2.on.aws"
fn_url_domain = Fn.select(
    0, Fn.split("/", Fn.select(1, Fn.split("https://", fn_url.url)))
)

distribution = cf.Distribution(
    self,
    "distribution",
    default_behavior=cf.BehaviorOptions(
        origin=cfo.HttpOrigin(fn_url_domain),
    )
)

Proposed Solution

The above code be added as a helper function on FunctionUrl construct:

fn_url_domain = Fn.select(
    0, Fn.split("/", Fn.select(1, Fn.split("https://", fn_url.url)))
)

Other Information

Happy to implement this one if it's a wanted change. Open to any suggestions on code or property names etc.

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

2.50.0

Environment details (OS name and version, etc.)

MacOS 13

[peterwoodworth]

The return value here comes from CloudFormation -

aws-cdk/packages/@aws-cdk/aws-lambda/lib/function-url.ts

Line 206 in 3d30cdb

this.url = resource.attrFunctionUrl;

We could add the domain prop to FunctionUrl using the same workaround you're using with intrinsic functions, thanks for the feature request 🙂

[diesal11]

I've opened #23046 which adds this functionality + a unit test.