ipython: add darwin-specific dependencies

[timbertson]

After the recent upgrade to jupyter (ipython 4), ipython fails on darwin due to missing packages which it tries to fetch during build. I've added these two pypi packages (appnope and gnureadline), and made ipython depend on them when stdenv.isDarwin. I've tested this locally, and it now works on darwin.

[copumpkin]

This looks like a bad edit...

[timbertson]

Oops I think that was a vim-fail. Fixed now.

[timbertson]

appnope only builds on darwin, so I've added that to its meta.platforms. gnureadline claims to work cross-platform, so it should be fine.

I've also removed the linux platform from pathpy, as the project works on windows (so surely it works cross-unix too).

/cc @bjornfor @FRidh

[FRidh]

I think you need to disable gnureadline for pypy since it doesn't support extension modules. It seems like the reason Travis is failing now.

[timbertson]

@FRidh thanks, for the tip - I've disabled it on pypy now.

I think travis actually failed because I missed the dependency on ncurses. gnureadline builds without it on darwin, but not on linux. I'm assuming that's actually due to impurities in the darwin stdenv, so I've included the dependency on all platforms now.

[FRidh]

Good. Could you put appnope and gnureadline in separate commits following the contributors guide.
http://hydra.nixos.org/build/26614434/download/1/nixpkgs/manual.html#idm139961959517936

Also, appnope needs a disabled = !stdenv.isDarwin.

[timbertson]

@FRidh Thanks, pulled out into separate commits now.

As for appnope, I've set meta.platforms = platforms.darwin - what does disabled do differently? There's one other use of platforms.darwin in python-packages.nix, and it doesn't use disabled for platform restrictions either.

[timbertson]

Hmm, not sure why travis is failing now - it's the same code as a previously successful run, sliced into different commits. Looks like it's checking the PR, but a 'title' key is missing. Am I missing something from this PR, or is it just a transient issue?

[FRidh]

https://nixos.org/wiki/Contributing

meta.platforms will tell Hydra to build binaries for specific platform targets. By default Hydra doesn't build anything. Don't set platforms.all or platforms.unix unless you've tested on both Darwin and Linux.

meta.platforms apparently says whether Hydra should build binaries, disabled whether or not it is a valid derivation at all.

[timbertson]

@FRidh platforms isn't just used for hydra, though:

$ nix-build --no-out-link -A pythonPackages.appnope '<nixpkgs>'
error: Package ‘python2.7-appnope-0.1.0’ in ‘/home/tim/dev/nix/nixpkgs/pkgs/development/python-modules/generic/default.nix:65’ is not supported on ‘x86_64-linux’, refusing to evaluate.

This is why I needed to remove platforms.linux (in this PR) to get ipython building on darwin.

I'm happy to add it if it's necessary, but it seems like it isn't, and might confuse people if we start doing that now - currently all of the disabled expressions this file are for specific python versions / interpreters, even though there are plenty of packages with limited platforms.

[timbertson]

So, anyone know why the travis build is failing? It's consistently getting:

=== Checking PR

Traceback (most recent call last):
    [ ... ]
  File "/home/travis/build/NixOS/nixpkgs/nox/nox/review.py", line 96, in review_pr
    click.style(payload['title'], bold=True)))
KeyError: 'title'

The command "./maintainers/scripts/travis-nox-review-pr.sh build" exited with 1.

[vcunat]

Note that travis checks on our PRs tend to be unreliable and they're not a requirement for merging.

[timbertson]

In that case, can this be merged?

[vcunat]

I suppose so. Darwin users seem uninterested, unfortunately.