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npm and iojs with new es6 features #269
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how about a |
@JonathonOng: Yeah, I discussed that in paragraph 4, but it does have user experience issues. Do you have thoughts on those? That also won't provide a solution to other kinds of iojs incompatibility that may not be coming this month, but could happen. |
I think that there is potential for io.js to introduce new apis not directly tied to V8 that may also lead to this situation. Ultimately, all new features introduces by io.js not available under node would likely require a There is some overlapse with the |
I'm -1 on using engines for this. Best practice is for module authors to feature detect when possible, this would encourage them not to do that. There actually should be a "cost" to using new features prior to them being widely adopted but I wouldn't rule out the possibility of people creating tooling for older versions of node that check for modules using new features and compile them down to ES5. |
Agreed. Several packages targeted at node 0.11 (especially for generators stuff) are recommending users to rely on transpilers such as |
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I agree that testing v8 versions doesn't really give you any more information since there now will be combinations of what flags io.js (or node.js) is started with. @mikeal how about exposing those features through package.json somehow? That at least give package to package feature dependencies over doing it within the modules (I can see scenarios where it wouldn't make sense to test for certain features since you'd probably wouldn't even install it in the first place without the feature in place). These entries could probably even be generated. |
It is possible to automatically find out version of V8 (and any other parameters that affect compatibility) from specified engine and version, and use it, when later there will be another version compatible with specified. For example, if specified And when you will install this package on |
@sunflowerdeath npm could certainly keep a table of iojs and node versions and their associated v8 versions, and so translate iojs >= 1.0.0 into v8 >= x.x.x. I don't think we currently can see other parameters that effect compatibility though. But yeah, io.js could expose those, but for that to work node.js would also have to be convinced to expose them. |
I'd love to see both - a consistent "engines" notation, which indicates what it's been /tested/ on, and a parallel "features" notation (I do not care about the name, bikeshed all you want), which indicates which JS features it depends on. Then it's left up to the npm cli, or the transpiler, or the saas platform, or whatever (or some npm module) to determine dynamically what is required to make the module work, or whether it's possible at all. Thoughts? |
Currently, all my packages that use generators have a |
I'm not thinking "magic" as much as "documentation" - your approach is great, but how am I to know that's the format you've used? As described, I'd have to duck type it, whereas with a |
adding more metadata to package.json about language features used, or v8 versions tested against/supported:
These are all fine, so long as you are vigilant about updating your package.json, but if we're honest, most people aren't. automating detection of features used:
This seems like a really, really bad thing to bake into npm, and probably not a very good thing to do in an individual project either (although it's obviously up to you to make the call on how you ship your project) |
Yes, oh 1000 times yes. That being said it wouldn't be bad practice (although not required) for something in package.json for batch scripts doing analytics. Not everything can be polyfilled via a transpiler. For those things I wouldn't want |
👍 for using |
I'd prefer if |
How about something similar to an npm preinstall script? That script will be written in ES5 and does ES6/V8 feature detection. If any error is thrown, then That way feature detection can be as complicated as anyone likes, and npm packages can make sure certain features exist before being installed. |
I would prefer having the extra metadata in package.json for non-standard features. At least as a console warning so the consumer knows to fetch the appropriate polyfill or upgrade their platform version. |
@greim Anything where the main require isn't commonJS is just not going to get adopted by the community, imo. The vast majority of module builders are going to be in ES5-land for a long time. |
@ljharb Is (BTW I'm not suggesting npm should auto-transpile things to es5 for everyone; only suggesting a convention module authors could follow.) |
@greim It is, but the main require - the default if i require the module by name with no slashes. |
@ljharb please don't do preinstall scripts, it's bad enough that we can't take them out of npm. |
I definitely don't advocate preinstall scripts. I fully agree with your comment. |
Related: #253 (comment). It suggest that the solution is |
I've mentioned a like idea in the tail of #90, and opened a quickly-shut follow-up ticket specifically on this issue npm/npm#90. @nathan7 @indexzero @mikeal what kills me about the "be a smart author" route- such as the As someone bundling es6+es5 apps and transpiling them myself, minifying them, and otherwise preparing them for deployment, I really don't want that extra baggage to be dealt with at all by the library- I'd rather have a library that just targets ES6, know that it targets ES6, and work that into my toolchain, rather than have a library "help" me by using transpiler X to do the job. The preferred default state for a package is as simple as possible. Anything any author does to make their package fit for consumption is going to make it harder for me the consumer to overwrite the baked in assumptions & impose the choices I'm making in my distribution. I don't want to deal with your source maps, I don't want to deal with your transpiling- I just want javascript, and my build-chain will handle these things as I feel appropraite. I see the "put more complexity on the package" versus "simple packages" as a AMD 2.0 debate: I'd way rather make authorship dumb/simple, and leave questions of processing to as late as possible, at the responsibility of the consumer & their chosen build-chain. Otherwise too many assumptions get baked into each package. |
@rektide we can bundle all of this complexity into a package of its own that you simply include. the AMD approach isn't the npm approach. |
Example feature-detection package: has-generators // foo.js
module.exports = require('has-generators') ? require('./foo.es6') : require('./foo.es5') |
If your stuff requires multiple ES6 things, |
Since io.js is going to be getting a new v8, and thus a slew of new es6 features not previously enabled by default, this is going to create a situation where some modules will only work with io.js, at least, until such time as node.js updates its own v8.
The feature in npm that currently handles this kind of thing is package.json engines field.
Now there’s an obvious problem if we add an “iojs” engine type: future versions of node will be likely be api & v8 compatible with iojs, and so depending on a specific iojs version would incorrectly block those node versions.
If adding an “iojs” engine type is out, another option would be to add a “v8” engine type. This would solve the immediate problem, but end users don’t ordinarily think or care about v8 versions, and telling them “your v8 is too old” would be a very crappy user experience (and wouldn’t give them any immediate information on how to fix the problem).
So a third option would be to create a series of “feature-xxx”* modules (eg feature-generators) that have preinstall scripts that fail with meaningful messages if you try to install them in an environment without the feature. These wouldn’t import functionality, obviously, they’d just assert a engine that can handle the feature. Further, if one desired to, even in-development features could easily be supported with major version bumps as their implementation changes.
* Perhaps not actually "feature-xxx", another prefix would do just as well, maybe even just "v8-xxx"?
What do you all think? Do you have other ideas on how we might handle this?
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