* SV variants are evaluated correctly in `when=` statements fixes#4113
The problem here was tricky:
```python
spec.satisfies(other)
```
changes already the MV variants in others into SV variants (where
necessary) if spec is concrete. If it is not concrete it does
nothing because we may be acting at a pure syntactical level.
When evaluating a `when=` keyword spec is for sure not concrete
as it is in the middle of the concretization process. In this case we
have to trigger manually the substitution in other to not end up
comparing a MV variant "foo=bar" to a SV variant "foo=bar" and having
False in return. Which is wrong.
* sv variants: improved error message for typos in "when=" statements
Modifications:
- added support for multi-valued variants
- refactored code related to variants into variant.py
- added new generic features to AutotoolsPackage that leverage multi-valued variants
- modified openmpi to use new features
- added unit tests for the new semantics
## Motivation
Python installations are both important and unfortunately inconsistent. Depending on the Python version, OS, and the strength of the Earth's magnetic field when it was installed, the name of the Python executable, directory containing its libraries, library names, and the directory containing its headers can vary drastically.
I originally got into this mess with #3274, where I discovered that Boost could not be built with Python 3 because the executable is called `python3` and we were telling it to use `python`. I got deeper into this mess when I started hacking on #3140, where I discovered just how difficult it is to find the location and name of the Python libraries and headers.
Currently, half of the packages that depend on Python and need to know this information jump through hoops to determine the correct information. The other half are hard-coded to use `python`, `spec['python'].prefix.lib`, and `spec['python'].prefix.include`. Obviously, none of these packages would work for Python 3, and there's no reason to duplicate the effort. The Python package itself should contain all of the information necessary to use it properly. This is in line with the recent work by @alalazo and @davydden with respect to `spec['blas'].libs` and friends.
## Prefix
For most packages in Spack, we assume that the installation directory is `spec['python'].prefix`. This generally works for anything installed with Spack, but gets complicated when we include external packages. Python is a commonly used external package (it needs to be installed just to run Spack). If it was installed with Homebrew, `which python` would return `/usr/local/bin/python`, and most users would erroneously assume that `/usr/local` is the installation directory. If you peruse through #2173, you'll immediately see why this is not the case. Homebrew actually installs Python in `/usr/local/Cellar/python/2.7.12_2` and symlinks the executable to `/usr/local/bin/python`. `PYTHONHOME` (and presumably most things that need to know where Python is installed) needs to be set to the actual installation directory, not `/usr/local`.
Normally I would say, "sounds like user error, make sure to use the real installation directory in your `packages.yaml`". But I think we can make a special case for Python. That's what we decided in #2173 anyway. If we change our minds, I would be more than happy to simplify things.
To solve this problem, I created a `spec['python'].home` attribute that works the same way as `spec['python'].prefix` but queries Python to figure out where it was actually installed. @tgamblin Is there any way to overwrite `spec['python'].prefix`? I think it's currently immutable.
## Command
In general, Python 2 comes with both `python` and `python2` commands, while Python 3 only comes with a `python3` command. But this is up to the OS developers. For example, `/usr/bin/python` on Gentoo is actually Python 3. Worse yet, if someone is using an externally installed Python, all 3 commands may exist in the same directory! Here's what I'm thinking:
If the spec is for Python 3, try searching for the `python3` command.
If the spec is for Python 2, try searching for the `python2` command.
If neither are found, try searching for the `python` command.
## Libraries
Spack installs Python libraries in `spec['python'].prefix.lib`. Except on openSUSE 13, where it installs to `spec['python'].prefix.lib64` (see #2295 and #2253). On my CentOS 6 machine, the Python libraries are installed in `/usr/lib64`. Both need to work.
The libraries themselves change name depending on OS and Python version. For Python 2.7 on macOS, I'm seeing:
```
lib/libpython2.7.dylib
```
For Python 3.6 on CentOS 6, I'm seeing:
```
lib/libpython3.so
lib/libpython3.6m.so.1.0
lib/libpython3.6m.so -> lib/libpython3.6m.so.1.0
```
Notice the `m` after the version number. Yeah, that's a thing.
## Headers
In Python 2.7, I'm seeing:
```
include/python2.7/pyconfig.h
```
In Python 3.6, I'm seeing:
```
include/python3.6m/pyconfig.h
```
It looks like all Python 3 installations have this `m`. Tested with Python 3.2 and 3.6 on macOS and CentOS 6
Spack has really nice support for libraries (`find_libraries` and `LibraryList`), but nothing for headers. Fixed.
* Make dia build w/ Spack's X bits (and misc)
X related
- need to depend on the +X variant of gtkplus
- need to depend on freetype
misc
- fix path to tarball
* Make freetype a "build" dependency
* Freetype is not just a build dep
* ncurses package will build ncurses and ncursesw
* Added libs property to ncurses, added fix for hstr
* flake8 is a harsh mistress
* make libs() more robust
* atop depends on ncurses
* fish depends on ncurses
* libtermkey and nano depend on ncurses
* Adjust url spacing
* Added a patch to the openblas package to change the openmp flag for
icc to qopenmp.
* Fixed a linking problem where when using Intel compilers, it was still
pulling in -lgfortran
* depend on readline, remove hardcoded -ltermcap
Bowtie should use Spack's readline and not explicitly depend on the
system termcap (which, on CentOS, leads to linking against the
system's tinfo library).
* Add depends_on('zlib')
* Add conflict with gcc@6:
Build seems to have trouble with 6's migration to -std=gnu++14.
* Dia requires libxml2.
* Clean up dependencies for Dia (and add X11 deps).
+ Remove dependencies on cairo and libpng. The will be satisfied via gtkplus.
+ Add dependencies on X11 libraries: libsm, libuuid, libxinerama, libxrender.
+ From a dependency diagram, it doesn't appear that we need libxml2 since this
dependency should be come in through cairo (via gtkplus). However, Dia will
not build without it.
