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Oh this was the diff code that I copied from one of the examples. Weird how there is no kind of stack trace.

Hmmm it's actually from a `&lt;pulumi.output.Unknown object at 0x1120840d0&gt;`. I thought in the `diff` method that all inputs would be resolved by that point?

Arggg. This has come back to haunt me again. Why would a property that is being passed to `diff` be `pulumi.output.Unknown`? Shouldn't they be resolved by that point?

Do you have sharable code? I don't think that error message is specific enough to help diagnose.

I just put it up on <https://gist.github.com/steinybot/ab1c9aafc2bfd230b4994d9720af136e>. Sorry that it isn't simplified.

The problem is in `WriteFile`. Where `connection` is something like:
```{'username': 'ec2-user', 'private_key': &lt;pulumi.output.Unknown object at 0x109530190&gt;, 'host': '<http://example.com|example.com>', 'private_key_passphrase': &lt;pulumi.output.Unknown object at 0x109530100&gt;}```
It' probably that I am doing the secret properties wrong.

Looks like you're serializing a dictionary with Input values. I think you'll need to serialize those individually...

You may need to write a ToString (or whatever the equivalent is in Python) that uses `apply` to render the string.

It seems to work find if I don't use secret values so I don't think it is just a problem of using `Input` in a dictionary.

Spoke too soon. Maybe it doesn't work without secrets.

Secrets would make me more confident in my idea. You have to render secrets yourself: Pulumi does its best to not render secrets in this sort of situation. You have to override it yourself.

Those values are coming from the `create` in the `GenerateSSHKey` resource. So if the plan is to create the `GenerateSSHKey` resource which is outputting those secrets then I'm guessing those values are not going to be available in the `diff` of the `WriteFile` resource which depends on those?

I'm afraid I don't know the lifecycle around `diff`. Is that a Python thing? The values won't be available synchronously, only in an `apply` block. But since they're only secrets and not dependent on a cloud resource, the `apply` shouldn't be dependent on anything and should be able to run immediately.

I don't think it is Python specific: <https://www.pulumi.com/docs/intro/concepts/programming-model/#diff-id-olds-news>

It would make sense that the outputs of one resource are not available to the other during the planning stage.

Yeah ok so treating `pulumi.output.Unknown` as a difference during `diff` seems to do the job.

That seems to match how resources from other providers work.