# terraform-template-renderer

Provides a ruby executable which will take a path to an ERB template as it's only positional argument and render that
with a json blob passed in to STDIN. The keys in the json blob will be used as instance variable names to use in the
template.

The result will be returned inside a json blob with a single key, the name of which is rendered.

For example if your template is

    Hello <%= @my_key %>!

And you execute the command as:

    echo '{ "my_key": "dear reader" }' | template_renderer path_to_my_template

You will produce

    { "rendered": "Hello dear reader!" }

The purpose for this strange behaviour is to be a [terraform external
provider](https://www.terraform.io/docs/providers/external/data_source.html) to render arbitrarily complex templates,
terraform passes in the variables to render as a json blob to stdin as described above and expects a json blob
back.

## Rendering Partials

Inside any template you can render a partial template by calling the render method.

For example if you have a partial template in filepath `partials/partial.erb`:

    This is a partial, Hello <%= name %>

And your template is

    My favourite colour is <%= colour %>
    <%= render 'partials/partial.erb' %>

And you execute the command as

    echo '{ "colour": "purple", "name": "Jonathan" }' | template_renderer path_to_my_template

You will produce

    { "rendered": "My favourite colour is purple\nThis is a partial, Hello Jonathan\n" }

## ERB Template notes

Trim mode is enabled and the trim character is a hyphen `-`.

## Examples

There are a number of examples in the examples folder. To run these examples you will need terraform 0.11, you can run
the example as follows:

    cd examples/simple_strings
    terraform init
    terraform apply

In each example there is an erb template and a terraform file, applying the terraform code will produce a file called
`example_output`.

___WARNING___: Some of the examples incur AWS costs, _ALWAYS_ remember to `terraform destroy` after you have finished
running the example. You are solely responsible for any AWS costs incurred running these examples.