feat: make build scripts compatible with Bash strict mode

[KenDJohnson]

First off, this is an awesome project and exactly what I was looking for; thanks!

I made a change to allow argc to work with scripts written for "Bash strict mode" (link), specifically set -u, which will cause a script to exit with an error when referencing an undefined variable.

The only requirement for this is to change $maybe_undefined to ${maybe_undefined:-}, to provide a default value (empty string) when the variable is null/undefined.

Bumped the version to 1.18.0, all cargo test tests are passing locally.

Edit: it looks like there may be some more instances of this, I am tracking them down and converting this to a draft in the meantime. As an alternative approach, the argc generated functions could start by saving the state of nounset, disabling it with set +u, and then restoring it at the end of the function. Let me know if you'd prefer this approach and I can change the implementation.

[sigoden]

1. Don't dump the version of argc. This has nothing to do with the PR. Normally we only upgrade versions when the next version is released.

2. You can not simply add ${:-} to all variables. No one writes scripts like this. Can you specialize only variables that may be undefined?

[KenDJohnson]

Don't dump the version of argc. This has nothing to do with the PR. Normally we only upgrade versions when the next version is released.

Reverting; sorry about that, habit from internal practices.

You can not simply add ${:-} to all variables. No one writes scripts like this. Can you specialize only variables that may be undefined?

This isn't adding ${:-} to all the variables, only the ones that may be legitimately undefined. For example, with env_name as FOO the [[ -n "${env_name}" ]] check would be written as [[ -n "$FOO" ]]. Up to this point, FOO is never assigned a value by the script, it is checking whether it was set externally. If the nounset option is enabled it has to be checked with [[ -n "${FOO:-} ]] to prevent the errors. Other variables (e.g. $_argc_index, $params, $arg_diff, etc.) are not potentially undefined and I did not add a default expansion.

It may be cleaner to save/restore the nounset state at argc generated function boundaries, which would eliminate the need for :- and doesn't risk missing instances that should have a default expansion with nounset.

[sigoden]

In principle, avoid adding ${:-} to variables unless necessary.

Variables requiring ${:-}, usually only apply to variables similar to $_argc_* and are defined in other functions.

argc/src/build.rs

Line 67 in 0cfaaad

[[ $_argc_dash -gt 0 ]] &&

For variables defined within the function, we should set default values during their initialization with local.

[KenDJohnson]

I've pushed up some additional changes that should address everything here.

I think the minimum scenarios where ${:-} is required are:

1. the $_argc_* possibly defined in other functions that you mentioned
2. the ${!name} references where the referenced var may not exist
3. indexing arrays such as argc__args, argc__positionals, where there may not be a value at that index
4. the ${{{var_name}}} instances that are potentially set outside of the generated script

I've changed others like $concatenated_choices and $missed_envs to set a default in the local definition.

I also added -u to the test runner so that it runs all test scripts with the nounset option set. This required a couple of changes in the tests in tests/validate.rs, but is otherwise working with the src/build.rs changes noted above.