Cannot create a template with a component and variables

[kate-goldenring]

Problem

I cannot create a template that contains a component that requires variables. Specifically, I am trying to update the KV explorer to use the config store for user/pass credentials, which requires adding variables to the template: fermyon/spin-kv-explorer#27.

This shows up in the Spin tests if you update update the add-variables test template as done here to include a component that requires the variables added via variables.txt. If you then run the manager::tests::can_add_variables_from_template test, it errors with

thread 'manager::tests::can_add_variables_from_template' panicked at 'called `Result::unwrap()` on an `Err` value: liquid: Unknown variable
  with:
    requested variable=secret
', crates/templates/src/manager.rs:1017:50

It seems we may need to expand upon variables support in templates (added here #1864) to consider the case when a component is being added.

Solution

I tried updating the renderer and writer to process "variables" first but was not successful.

[itowlson]

In your sample, this happens because in the line

kv_credentials = "{{ secret }}"

the template system sees {{ secret }} as a reference to a template variable. Double braces need to be escaped. From initial tests,

{% raw %}kv_credentials = "{{ secret }}"{% endraw %}

at least doesn't error; I will update the unit test to verify it produces the right result. I should also update the docs to tell people how to do this!