Handling arrays of aliases

[benfletcher]

When the minimist-options package parses aliases, it was apparently designed to handle both a single string as well as an array of strings (it arrifys the alias and turns a single string into an array before processing). (This package was also written by @sindresorhus, but the original minimist handled aliases similarly.)

That is quite convenient if you want multiple aliases for a single option.

However, it creates some inconsistent behavior in the latest version with unnormalizedFlags. If you have more than one alias for a flag, those items (the flag and all aliases) get included in cli.flags as well as unnormalizedFlags. If there's only one alias (either a single element array or a plain string), the normal behavior of the alias being excluded from flags is observed.

The ability to pass in an array into aliases is admittedly an undocumented, if not unsupported, feature, but for me it's quite helpful. In particular it helps with backwards compatibility and gradual deprecation of flags that have been renamed. I can support both the old and new flag names for 1-2 versions while warning of the deprecation, without having to rewrite the underlying code.

The current behavior is not difficult to deal with, once known. I am seeking to raise awareness of the handling of alias arrays and propose that it become a documented and supported feature.

[benfletcher]

I created a PR #132, in case arrays of aliases is desired functionality.

[sindresorhus]

For anyone that wants to work on this, see initial attempt and feedback here: #131

[tommy-mitchell]

@sindresorhus I think this was handled with #226.