N-API: Reuse ObjectTemplate used for napi_wrap()

[gabrielschulhof]

V8 caches and does not subsequently release ObjectTemplate instances.
Thus, we need to store the ObjectTemplate from which we derive object
instances we use for napi_wrap() in a persistent in the napi_env.

Re nodejs/node-addon-api#70 (comment)

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

N-API

[gabrielschulhof]

This means we will have one ObjectTemplate per N-API module, because we have one napi_env per N-API module.

[gabrielschulhof]

Whoops! Wrong template :) BRB

[gabrielschulhof]

Hmmm ... we actually use more than one ObjectTemplate. Need to store 'em all on the napi_env.

[gabrielschulhof]

OK, now we're good. Three ObjectTemplate instances stored on the napi_env. So, three ObjectTemplate instances per module. Granted, they're lazy, so an ObjectInstance is only created if

• a module does any wrapping (not necessarily though often)
• a module implements accessors (perhaps more rarely)
• a module exports native functions (almost always)

[bnoordhuis]

Can you indent by 4 spaces?

[mhdawson]

LGTM

[mhdawson]

CI run: https://ci.nodejs.org/job/node-test-pull-request/9010/

[mhdawson]

Landed as 29df1a8

[addaleax]

@gabrielschulhof @mhdawson Just so you know, if you don’t provide the subsystem in the commit message in lowercase the tooling won’t group it properly in the changelog – not a big deal, just something for the future. :)

[gibfahn]

if you don’t provide the subsystem in the commit message in lowercase the tooling won’t group it properly in the changelog – not a big deal, just something for the future. :)

If we don't have any uppercase subsystems (which I think is the case) then maybe core-validate-commit could check for that.

[evanlucas]

it checks for a certain set of subsystems, so it should have failed for that as well.

  ✖  29df1a87fa230bc86f460620173b9fedd2919f68
     ✔  0:0      skipping fixes-url                        fixes-url
     ✔  0:0      blank line after title                    line-after-title
     ✔  0:0      line-lengths are valid                    line-length
     ✔  0:0      metadata is at end of message             metadata-end
     ✔  0:0      reviewers are valid                       reviewers
     ✖  0:0      Invalid subsystem: "N-API"                subsystem
     ✔  0:0      Title is <= 50 columns.                   title-length

:]