doc: make doc-only -> fallback to user binary

[eljefedelrodeodeljefe]

Checklist

• tests and code linting passes
• a test and/or benchmark is included
• documentation is changed or added
• the commit message follows commit guidelines

Affected core subsystem(s)

build, doc

Description of change

Fixes:
When checking out a fresh clone or rm -rf out/ or rm ./node make doc-only was not working (Mac OS), failing to find ./node. I think this has slipped, because likely contributors have at least some binary, from e.g. a build of another branch still in out/.

This then would check if $(NODE) was set correctly take it or fallback to a user pre-installed node binary.

Bash syntax and implementation is a little too clever unfortunately, but I guess that won't hurt anyone there.

[addaleax]

This won’t really work like you want it to, [ $(foobar) ] only checks that foobar is nonempty, not that it corresponds . It should probably be something like [ -x "$(NODE)" ] to make sure that the file is there + executable.

Or you just leave the check out, || takes care of a failure in the first version anyway…

[eljefedelrodeodeljefe]

Didn't know about -x. Thought -n, -z or nothing at all would be appropriate . amended

[eljefedelrodeodeljefe]

@addaleax output is ugly though.

[ -x ./node ] && ./node tools/doc/generate.js --format=json doc/api/vm.md > out/doc/api/vm.json || node tools/doc/generate.js --format=json doc/api/vm.md > out/doc/api/vm.json
Input file = doc/api/vm.md

Do you think having it in ifdefs is better?

[addaleax]

@eljefedelrodeodeljefe Makefile output is never truly beautiful. :)

It works, so LGTM.

[eljefedelrodeodeljefe]

@jasnell because of #3888, could I have your review on this one?

[eljefedelrodeodeljefe]

cc @nodejs/build extending #3888 a little to fallback to user binary.

[MylesBorins]

This seems reasonable enough. Works on my machine.

If we are going to be doing this we may want to give some sort of better error if node doesn't exist on the system.

LGTM either way.

[eljefedelrodeodeljefe]

Landed in c111cf2. I have some work for error handling in mind. For now I think something like "node not found" is okay and better than "./node not found"