Fix count interpolation with computed values

[greenboxal]

This commit enables the use computed values when interpolating
the count special variable.

This is achieved by defering the expansion of count during
walkInput and walkValidate as the real value isn't necessary
at this point.

The value will be resolved during walkRefresh and DynamicExpand
will work as expected.

Partially fixes #3888.

@edit
I'm not sure on how write tests for this. I tested with this snippet and it works: https://gist.github.com/greenboxal/113469077550fa1f6c65d4db7f22ba27

Can someone guide me on this?

[mitchellh]

This is a good set of information, but I think for input and validate we'll have a good solution when we switch to a new graph that simply ignores the count variable full out. :) refresh, input, and validate are still using the old graphs!

If this works for you though, feel free to patch and use it.

Thanks for the input! :)

[greenboxal]

@mitchellh Nice. Do you have any prevision on when this will be available?

For now, I'll keep using this solution.

[mitchellh]

Was hoping we could get it into 0.8 but the freeze came up on us. :)

So, 0.9, probably released as an experimental feature behind a flag in 0.8.x sometime.

[cemo]

@mitchellh will this issue be fixed with 0.9? You have recently implemented a dozen features and this is a really huge problem for terraformers.

[mitchellh]

I'm hoping it improves with 0.9, but I'm not 100% sure. 0.9 betas will start in Feb and we need to get it in before that window. I'm trying though!

[cemo]

We are grateful for the all thing you have done. Thank you again.

[ghost]

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