Node, iojs and npm formula resolution

[bcomnes]

I'm aware of the historical baggage of a separate npm formula, but I think the introduction of iojs warrants at least revisiting this solution taking into what has been learned from the current node formula. I appreciate your consideration in advance. If this is just too wacky, I understand, but I believe its a step forward.

This PR:

• separates npm into its own formula
• applies the minor patch needed to make npm compatible with iojs.
  • the patch is still compatible with joyent node: http://logs.libuv.org/npm/2015-01-28#21:53:34.823
• sets npm's "prefix" to #{HOMEBREW_PREFIX}, replicating existing npm tarball install behavior. (this part is key)
  • this results in npm installing modules into #{HOMEBREW_PREFIX}/lib/node_modules which then link to #{HOMEBREW_PREFIX}/bin
• takes iojs out of its keg-only status
• conflicts iojs with node, so they can't be linked at the same time.
  • advanced brew users can unlink and link in and out the version they want, if the choose to have both built at the same time.
• reduces over all complexity of the three formulae imo.

Issues that still need resolution:

• the npm formula should depend on node OR iojs. Right now, it only depends on node. I don't know how to do this. Can someone help me wrangle Library/Homebrew/requirements.rb to enable this?
• [ ] Neither iojs or node "depend" on npm. But it should probably be installed automatically with these unless told not to. Is there a way to do that? Right now I just added a caveat instructing people to brew install npm.
• Find out if there is any way to happily install npm to the cellar.
• Fix testing errors

Why this arrangement works well

• users can either brew install node OR brew install iojs and everything "just works". I believe this will resolve the recent pushback related to iojs formula as this puts the two projects on equal footing.
• npm can be installed and patched according to the needs of homebrew and a dependency chain can be enforced.
• users are free to install global npm modules, and these stay out of the way of homebrew's npm cellar.
• npm is free to update itself (eg npm install -g npm@latest or npm install -g npm@next) and it works as well as it should.
• brew doctor does not start to complain after npm updates itself.
• brew can update npm and it works the way one would expect.

Wackiness

• updating npm with npm installs a second copy of npm into #{HOMEBREW_PREFIX}/lib/node_modules.
• whichever method (brew update npm or npm install -g npm@latest) is run last will take precedence over which version of npm is used. Users can also use brew unlink npm && brew link npm to put brews npm back in place.
• Currently, updating npm with npm would undo the npm patch applied by brew. In the future, this wont be such a big issue as the npm devs are committed to keeping compatibility between iojs and node patches won't be needed.

As both a homebrew user and a node user, I don't find this wackiness to be unreasonable.

Current iojs formula discussions

• Adds flag to patch npm install for iojs compatibility  #36357 Patched npm install for iojs compatibility
• Node, iojs and npm formula resolution #36343 Node, iojs and npm formula resolution
• Graduate iojs out of keg-only #36369 Graduate iojs out of keg-only

working iojs taps

• https://github.com/aredridel/homebrew-iojs

Past iojs formula discussions

• add iojs #35853
• iojs v1.0.3 (new formula) #36039
• Adds iojs formula meeting requests by @mikemcquaid #36193

npm formula issues:

• npm #3762
• Homebrew installed npm can't upgrade itself #22408
• Homebrew should no longer manage npm. #27479
• node: install npm using tarball. #28075

Extra thanks for all the info and help from @othiym23, @mistydemeo, @DomT4, @rvagg, @aredridel and @MikeMcQuaid

[MikeMcQuaid]

the npm formula should depend on node OR iojs. Right now, it only depends on node. I don't know how to do this. Can someone help me wrangle Library/Homebrew/requirements.rb to enable this?

Basically both just need a Requirement that looks for which("node").

Neither iojs or node "depend" on npm. But it should probably be installed automatically with these unless told not to. Is there a way to do that? Right now I just added a caveat instructing people to brew install npm.

Yeh, that's my main objection to this. We don't really support this model and it doesn't really fit with other similar packages. If we can work out a way that node and iojs wouldn't hate then having npm installed to the node Cellar again may be a better possible solution.

[bcomnes]

I got a bit of tunnel vision working on this last night. I have another idea that might work well, I'll send a parallel PR to this later.

I'll research npm configuration a bit more today.

[bcomnes]

Symlinking #{Formula["iojs"].opt_lib}/node_modules/npm to #{HOMEBREW_PREFIX}/lib/node_modules/npm didn't work. Link gets overwritten when npm updates itself.

[aredridel]

Wow. That wackiness actually sounds like a good status quo to me. If I tell either brew or npm to do something, it does it.

[bcomnes]

@aredridel It does leave the possibility for one system or the other to leave a bunch of symlinks in the way of the other, resulting in the need to run a brew prune or brew link --force. Thats what I mean by weirdness.

[bcomnes]

I back-ported patch changes that I learned from this PR to the existing formula: #36357

[bcomnes]

Closing in favor of #36369 for now.