Add testing suite for configuration precedence and omission testing

[f4z3r]

Related Issues

#16

Consumer Impact

None

[f4z3r]

I am not quite done with the testing, but wanted to make sure this is desired. I have the feeling this is the typical way to do this, instead of using the default from figment (which is a dot - .).

Not setting this does not allow configurations via the env vars as shown in the test below (https://github.com/wasmCloud/wash/pull/97/files#diff-f7f9d11319f33b9af91da4ef6ce4b7111c1baceef1b82db506c4612ba6f808b1R356). If this is removed, the test fails as the splitting does not work on underscores.

[f4z3r]

I will need to add a test on how this works on "multi-word" configuration options though such as here:

wash/crates/wash/src/component_build.rs

Line 48 in 0d7cde2

pub custom_command: Option<Vec<String>>,

[f4z3r]

I updated this to use two underscored (__) as the separator. Otherwise multi-word configurations cannot be parsed from the environment. This results in the following sample configuration via environment variables:

WASH_BUILD__RUST__CUSTOM_COMMAND="[cargo,build]"

The only slightly weird stuff is the single underscore in the prefix. We could update that to a double underscore as well to have it be consistent. Or do you see any other separator instead of double underscore that might make sense (note single underscore will not work properly) @brooksmtownsend ? The figment default is a dot, but this is not supported properly in many shells AFAIK.

[f4z3r]

Is it possible that the tests are slightly flaky? I am unsure I understand why the tests on Ubuntu fail. Regarding the tests on Windows, this is extremely weird. While the test CLI context creates a new temporary directory for every test that should host all files, it seems that on Windows some configurations are found in the test CLI context...?