Proposal: Harmony enabled binary, packages.

[rektide]

Greetings.

Some of us really want nothing to do with the old ES5 world and are wanting to make a clean hard break. I would like to see a node binary where harmony is the default. This could be a configuration variable at build time, it could be a node-harmony binary, or perhaps we're ready to throw the switch and just do it for everyone: something to avoid the sys-administration of wrapper shell scripts or project configuration needed to add --harmony.

For responsibility/compatibility sake, npm packages need some what to discern the target: engines might stand to have a harmony target that designates that a harmony targeting engine is needed.

Follow-up item: whether it's desirable or needed to have a --disharmony.

[bnoordhuis]

You can bake extra V8 options into the binary with ./configure --v8-options="--expose_gc --harmony". I don't think we'd ever want to enable it in releases, though.

See nodejs/node-v0.x-archive#6999, that's a trial PR I opened to get the discussion going. The conclusion was that --harmony features are generally half-baked (if not outright buggy) and that it's generally better to let them mature until they are no longer behind a flag. Generators and promises are examples of that.

--disharmony

--noharmony should work.

[aredridel]

A completely different way to approach this -- to declare a dependency on a harmony supporting binary -- is to bring that binary in yourself:

npm install --save node-bin@0.11.14

Then --harmony will work for things run within your project via npm scripts.

Not exactly what you're asking, but has some of the same effects: declare what you're doing, and make it Just Work.

[caineio]

Hello!

I am pleased to see your valuable contribution to this project. Would you
please mind answering a couple of questions to help me classify this submission
and/or gather required information for the core team members?

Questions:

1. Issue-only Does this issue happen in core, or in some user-space
   module from npm or other source? Please ensure that the test case
   that reproduces this problem is not using any external dependencies.
   If the error is not reproducible with just core modules - it is most
   likely not a io.js problem. Expected: yes
2. Which part of core do you think it might be related to?
   One of: debugger, http, assert, buffer, child_process, cluster, crypto, dgram, dns, domain, events, fs, http, https, module, net, os, path, querystring, readline, repl, smalloc, stream, timers, tls, url, util, vm, zlib, c++, docs, other (label)
3. Which versions of io.js do you think are affected by this?
   One of: v0.10, v0.12, v1.0.0 (label)

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Caine.

Responsibilities

1. indutny: crypto, tls, https, child_process, c++
2. trevnorris: buffer, http, https, smalloc
3. bnoordhuis: http, cluster, child_process, dgram

[cjihrig]

Closing based on @bnoordhuis response.

[ruimarinho]

@bnoordhuis since V8 has introduced an es_staging flag to enable experimental (i.e. completed but not fully tested) features, the harmony flag will now only enable completed features. Theoretically, this makes it acceptable for node to be bundled with --harmony enabled on the release build considering the latest V8 version being shipped, specially since there is no evidence that this flag will go away when work on ES7 begins.

[rvagg]

do we have a catalogue of what --harmony currently enables?

[ruimarinho]

@rvagg: yes - on master (3.31.x) and on 3.30.37.

[bnoordhuis]

@ruimarinho Close but no cigar. :-) In V8 3.30 (what currently ships with io.js), --es_staging is --harmony minus --harmony_scoping; in 3.31, they are synonyms.

I personally don't really object to turning on --es_staging; in 3.30, you get the harmony string methods, like String#startsWith(), which is nice.

[ruimarinho]

@bnoordhuis ah, yes, just noticed that there was an update on that. Seems like --es_staging is a safe default for 3.30 then. Do you think that if it ends up being enabled on 1.0.0, would it make sense to keep the flag also enabled for later upgrades of V8 too (e.g. 3.31), now that there is a clear distinction between "in progress" and "completed" features?

Looking back at node 0.11.14 (V8 3.26.33), the only feature under staging was harmony_maths with pretty much everything else being a mixture of "in progress" and "completed" features, so I believe it was a reasonable decision at that time to not ship harmony by default.