feat(cache): accept multiple specs

[mjsir911]

This is a backwards incompatible change to the undocumented
cache add pkg version, but

Motivations for this can be found here:
#2976 (comment)

I attempted a discussion here but it didn't work out very well

Signed-off-by: Marco Sirabella marco@sirabella.org

[wraithgar]

It doesn't seem possible to do this in a way that is backwardly compatible, so shipping this in npm7 is probably not feasible.

It also does seem like in hindsight the args should just be package specs, instead of allowing a second param for the tag which is something the package spec already allows.

Trying to think of solutions here, and idk if I'm a fan of any of them but maybe a discussion will help shake something out

• if there are only two params, and neither have @ then work the old way. this is probably a nonstarter since it would make npm cache add pkg1 pkg2 not work, which is very counterintuitive
• require an @ in all params to invoke this behavior, this would allow the fallback behavior to make a little more sense but still seems clunky
• reuse the --package param currently used by npm exec and look there as a fallback if there are no bare args
• add a new add-multiple subcommand

[mjsir911]

Thank you for the quick feedback @wraithgar!

• if there are only two params, and neither have @ then work the old way. this is probably a nonstarter since it would make npm cache add pkg1 pkg2 not work, which is very counterintuitive

• require an @ in all params to invoke this behavior, this would allow the fallback behavior to make a little more sense but still seems clunky

Doesn't work for my use case unfortunately, I'm adding tarballs

• reuse the --package param currently used by npm exec and look there as a fallback if there are no bare args

• add a new add-multiple subcommand

I'm still feeling eh on both of these, but they seem feasible.

It also does seem like in hindsight the args should just be package specs, instead of allowing a second param for the tag which is something the package spec already allows.

That seems to be the consensus, and this behavior is undocumented.

It doesn't seem possible to do this in a way that is backwardly compatible, so shipping this in npm7 is probably not feasible.

Could a path forward be to deprecate the usage now and then implement this PR at a later date eg npm8?

Another backwards-compatible way to implement this is to only use this behavior on > 2 passed arguments. It's a bit wacky, and I think the 2 arg spec should still be deprecated but its a compromise

[wraithgar]

It does appear to be undocumented, both the -h and npm help cache don't show this usage.

[mjsir911]

@wraithgar Any thought on these proposals to maintain backwards compatibility:

1. Keep the previous behavior on 2 arguments, New behavior on > 2 arguments. This has the downside of being buggy on unknown number of files, like wildcards in directories
2. Somehow detect if the second argument is another spec or just a version portion of a spec. This is harder and I'm not sure if this is approachable

[wraithgar]

@mjsir911 thanks for your patience here. This was on our radar but took awhile to get to discussing. Since the old behavior was completely undocumented, we're going forward with this PR.