Previously, unless unsupported platforms were allowed, the following
would fail to evaluate (from an "x86_64-linux" system):
pkgsCross.x86_64-freebsd.__splicedPackages.docutils.__spliced.buildHost
It shouldn't have, because the buildHost package ends up being for
Linux. This broke evaluation of e.g. pkgsCross.x86_64-freebsd.libdrm,
because it has docutils in nativeBuildInputs. mkDerivation would try
to go through __spliced.buildHost on docutils to get to the Linux
version, but the check in ensurePythonModules would kick in first,
triggering the meta check because of the equality check in the
implementation of hasPythonModule, which would fail because Python is
not marked as supported on FreeBSD in Nixpkgs at the moment. Thus,
even though they're not supposed to be, the meta checks would be
triggered even though the only attribute being accessed on the
unsupported derivation was __spliced.
We can fix this by using the same mechanism used to implement the meta
checks themselves: lib.extendDerivation. Now, attempting to access
drvPath or outPath on an attribute that fails the validity check will
produce the same error as before, but other accesses will be allowed
through, fixing splicing.
I've tested evaluation of packages that pass and fail the validity
check, and confirmed that the behaviour is still correct.
It wasn't clear before, but it turns out that this is just four
separate conditions, and an attribute is valid if any of the
conditions is true, so we don't need a sea of parentheses to express
it.
Many packages have some kind of flag indicating whether or not to build with
systemd support. Most of these default to `stdenv.isLinux`, but systemd does
not build on (and is marked `broken` for) `isStatic`. Only a few packages have
the needed `&& !isStatic` in the default value for their parameter.
This commit moves the logic for the default value of these flags into
`systemd.meta.{platforms,badPlatforms}` and evaluates those conditions using
`lib.meta.availableOn`.
This provides three benefits:
1. The default values are set correctly (i.e. including `&& isStatic`)
2. The default values are set consistently
3. The way is paved for any future non-Linux systemd platforms (FreeBSD is
reported to have experimental systemd support)
checkInputs used to be added to nativeBuildInputs. Now we have
nativeCheckInputs to do that instead. Doing this treewide change allows
to keep hashes identical to before the introduction of
nativeCheckInputs.
fetchPypi doesn't use python under the hood and doesn't need to be tied
to a specific version of python. Moving it to top level makes it more
consistent with other fetchers and makes code generation easier.
