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this is with a simple `ec2.get_subnet_ids(vpc_id=vpc.id)` call

weird, the fargate example makes the exact same call. `vpc.id` is valid and compared the object with its use in other methods

```      File "/Users/scott/.pyenv/versions/infra/lib/python3.8/site-packages/pulumi/runtime/invoke.py", line 111, in do_invoke
        raise Exception(f"invoke of {tok} failed: {resp.failures[0].reason} ({resp.failures[0].property})")
    Exception: invoke of aws:ec2/getSubnetIds:getSubnetIds failed: "vpc_id": required field is not set ()
    error: an unhandled error occurred: Program exited with non-zero exit code: 1

    VPC ID before ec2.InternetGateway: &lt;pulumi.output.Output object at 0x10e577970&gt;
    VPC ID before deriving subnets for ec2.NatGateway: &lt;pulumi.output.Output object at 0x10e577970&gt;```

<https://gist.github.com/ohlol/8d96d7305d32e20304051a6f5d89c801>

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Yea - are you sure `self.vpc.id` is set or even that `self.vpc` is set?

When I try this it works fine for me.

<https://gist.github.com/ohlol/9b4923804c6de07ca1c5c23dfcd37d60> <@UDEJ1F5SQ> all of these methods work with the exception of `_manage_natgw` which raises the exception above

nb I tried `self.vpc` in that file on L38 because `self.vpc.id` didn’t work

can you provide the code that's calling all those functions?

<https://gist.github.com/ohlol/8a4d4bbad7b41788d86bbbaf790a0291>

here’s my stack config fwiw <https://gist.github.com/ohlol/f2912fe357d82511957886b71572f6c6>

Got this working with <https://gist.github.com/clstokes/1c42f23a666c183f1353282fa393c82a>. Note the `TODO`s that you'll want to change back.

There are a few things I changed:
- in `_manage_subnets` create a list of subnets and set them to `self`
- in `_manage_natgw` use the list of subnets from `self` to create the `NatGateway` resources
- removed the `ec2.get_subnet_ids()` call entirely

The reason why it wasn't working is that `self.vpc.id` is an Output (e.g. a "future") and `ec2.get_subnet_ids()` expects a "prompt" string. We have an issue somewhere to allow for the `get_X()` function calls to accept outputs, but unfortunately they don't currently.

More generally though, the `get_X()` functions actually query the AWS APIs to get data and if this is the first time you're running a `preview` or `up` those subnets won't actually exist.

Hope this makes sense, let me know if you have any questions.