feat: use undefined as fallback for string & number args with no values

[kricsleo]

resolves #142

This PR changes the fallback for string & number args from "" to undefined.

This change enables differentiation between user-specified values, such as: test --config vs test --config ""

Example:

  args: {
    name: {
      type: 'string',
    },
    age: {
      type: 'number',
    },
  },

Previously:

test --name => ctx.args.name === ""
test --name "" => ctx.args.name === ""
test --age => throws

Now:

test --name => ctx.args.name === undefined & ("name" in ctx.args) === true
test --name "" => ctx.args.name === ""

test --age => ctx.args.age === undefined & ("age" in ctx.args) === true

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (main@241b948). Learn more about missing BASE report.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #195   +/-   ##
=======================================
  Coverage        ?   94.10%           
=======================================
  Files           ?        7           
  Lines           ?      509           
  Branches        ?      166           
=======================================
  Hits            ?      479           
  Misses          ?       30           
  Partials        ?        0           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[pi0]

Can you add an (additional) test that ensures (by default) --flag sets to true

[kricsleo]

Updated.

[pi0]

~-1 == 0 while is valid, is really not readable we should use explicit -1 check

[kricsleo]

Done.

I replaced indexOf with includes and also updated other instances of ~.

[pi0]

Also to be honest i'm not sure if we should add string to parser level. there is need to distingoush between undefined|string|boolean but number is derived from string in upper layer by parsing string

[kricsleo]

Then maybe we need to add all the booleans into strings for processing.

For example:
opts.string = toArr(opts.string).concat(toArr(opts.number));
This could make the parser simpler. WDYT

[kricsleo]

Done.

Removed redundant processing here as the conversion from string to number has already been handled in upper layer.