[perf] nvm_print_versions: re-implement using awk

[ryenus]

As of now there are about 700 node versions according to nvm_remote_versions, for which nvm ls-remote might take up to 20 seconds to print the versions in a slightly formatted form.

We can get a significant performance improvement by replacing the major part of nvm_print_versions with a awk based implementation:

	Before	After
Main loop	real 17.163s user 6.635s sys 6.675s	real 0.183s user 0.108s sys 0.098s
Overall	real 18.555s user 6.984s sys 6.958s	real 1.671s user 0.508s sys 0.414s

[ryenus]

Tested using dash, both nvm ls and nvm ls-remote work as expected.
Interestingly that with this change nvm ls-remote is now faster than nvm ls.

[ljharb]

Can't say i understand all the awk code, but passing tests and some local testing should be sufficient :-)

[ljharb]

When i run this locally on my mac, i get:

awk: newline in string v0.1.14
v0.1.15
v0.1... at source line 1
awk: newline in string v0.1.14
v0.1.15
v0.1... at source line 1
awk: newline in string v0.1.14
v0.1.15
v0.1... at source line 1

are you using only features of posix awk? gnu-specific stuff won't be viable.

[ryenus]

Indeed, I just pushed a change to substitute newlines with | when passed through awk -v. And now it works well with /usr/bin/awk on Mac.

[ryenus]

BTW. about the failing tests on Travis, is it related to this comment?

[ljharb]

Works great, and wow, it really is lightning fast by comparison!

Travis tests are sadly a blocker, but it's being worked on in #2802.

[ljharb]

I'm probably going to try to migrate off of travis soon, since we've been blocked for months.

I agree the likelihood of this breaking is minimal, but it's not worth the risk to merge anything while tests aren't passing.

[ryenus]

I'm probably going to try to migrate off of travis soon, since we've been blocked for months.

Great, glad that we've moving forward, thank you!

[ljharb]

@ryenus it looks like some tests are failing for real; could you take a look?

[ljharb]

The tests pass now prior to this PR, so while i think you're right, i think a change here is still needed?

[ryenus]

Sure, I'll have a deeper look once I get a chance.

[ljharb]

The failure I see (https://app.travis-ci.com/github/nvm-sh/nvm/jobs/585309369#L566) is because the non-color output is missing the asterisks.

[ryenus]

@ljharb, the patch is finally in a good shape, there's a last minute change I needed to include, meanwhile I saw your formatting tweaks, which is totally ok for me. With that said, over to you now, thanks!

[tangkunyin]

When i run this locally on my mac, i get:

awk: newline in string v0.1.14
v0.1.15
v0.1... at source line 1
awk: newline in string v0.1.14
v0.1.15
v0.1... at source line 1
awk: newline in string v0.1.14
v0.1.15
v0.1... at source line 1

are you using only features of posix awk? gnu-specific stuff won't be viable.

So, did this be solved?

[ljharb]

@tangkunyin yes, that's been fixed in the PR.