This will allow e.g. channel expressions to use builtins.storePath IFF
it is safe to do so without knowing if the path is valid yet.
Signed-off-by: Shea Levy <shea@shealevy.com>
nix-shell with the --command flag might be used non-interactively, but
if bash starts non-interactively (i.e. with stdin or stderr not a
terminal), it won't source the script given in --rcfile. However, in
that case it *will* source the script found in $BASH_ENV, so we can use
that instead.
Also, don't source ~/.bashrc in a non-interactive shell (detectable by
checking the PS1 env var)
Signed-off-by: Shea Levy <shea@shealevy.com>
This reduces the difference between inherited and non-inherited
attribute handling to the choice of which env to use (in recs and lets)
by setting the AttrDef::e to a new ExprVar in the parser rather than
carrying a separate AttrDef::v VarRef member.
As an added bonus, this allows inherited attributes that inherit from a
with to delay forcing evaluation of the with's attributes.
Signed-off-by: Shea Levy <shea@shealevy.com>
nar.nix's builder depends on coreutils and nix itself being in $PATH.
Unfortunately, there's no good way to ensure that these packages exist
in the same place on the remote machine: The local machine may have nix
installed in /usr, and the remote machine in /usr/local, but the
generated nar.sh builder will refer to /usr and thus fail on the remote
machine. This ensures that nar.sh is run on the same machine that
instantiates it.
Signed-off-by: Shea Levy <shea@shealevy.com>
Evaluation of attribute sets is strict in the attribute names, which
means immediate evaluation of `with` attribute sets rules out some
potentially interesting use cases (e.g. where the attribute names of one
set depend in some way on another but we want to bring those names into
scope for some values in the second set).
The major example of this is overridable self-referential package sets
(e.g. all-packages.nix). With immediate `with` evaluation, the only
options for such sets are to either make them non-recursive and
explicitly use the name of the overridden set in non-overridden one
every time you want to reference another package, or make the set
recursive and use the `__overrides` hack. As shown in the test case that
comes with this commit, though, delayed `with` evaluation allows a nicer
third alternative.
Signed-off-by: Shea Levy <shea@shealevy.com>
The kill(2) in Apple's libc follows POSIX semantics, which means that
kill(-1, SIGKILL) will kill the calling process too. Since nix has no
way to distinguish between the process successfully killing everything
and the process being killed by a rogue builder in that case, it can't
safely conclude that killUser was successful.
Luckily, the actual kill syscall takes a parameter that determines
whether POSIX semantics are followed, so we can call that syscall
directly and avoid the issue on Apple.
Signed-off-by: Shea Levy <shea@shealevy.com>
mount(2) with MS_BIND allows mounting a regular file on top of a regular
file, so there's no reason to only bind directories. This allows finer
control over just which files are and aren't included in the chroot
without having to build symlink trees or the like.
Signed-off-by: Shea Levy <shea@shealevy.com>
It is surprisingly impossible to check if a mountpoint is a bind mount
on Linux, and in my previous commit I forgot to check if /nix/store was
even a mountpoint at all. statvfs.f_flag is not populated with MS_BIND
(and even if it were, my check was wrong in the previous commit).
Luckily, the semantics of mount with MS_REMOUNT | MS_BIND make both
checks unnecessary: if /nix/store is not a mountpoint, then mount will
fail with EINVAL, and if /nix/store is not a bind-mount, then it will
not be made writable. Thus, if /nix/store is not a mountpoint, we fail
immediately (since we don't know how to make it writable), and if
/nix/store IS a mountpoint but not a bind-mount, we fail at first write
(see below for why we can't check and fail immediately).
Note that, due to what is IMO buggy behavior in Linux, calling mount
with MS_REMOUNT | MS_BIND on a non-bind readonly mount makes the
mountpoint appear writable in two places: In the sixth (but not the
10th!) column of mountinfo, and in the f_flags member of struct statfs.
All other syscalls behave as if the mount point were still readonly (at
least for Linux 3.9-rc1, but I don't think this has changed recently or
is expected to soon). My preferred semantics would be for MS_REMOUNT |
MS_BIND to fail on a non-bind mount, as it doesn't make sense to remount
a non bind-mount as a bind mount.
/nix/store could be a read-only bind mount even if it is / in its own filesystem, so checking the 4th field in mountinfo is insufficient.
Signed-off-by: Shea Levy <shea@shealevy.com>
The generated attrset has drvPath and outPath with the right string context, type 'derivation', outputName with
the right name, all with a list of outputs, and an attribute for each output.
I see three uses for this (though certainly there may be more):
* Using derivations generated by something besides nix-instantiate (e.g. guix)
* Allowing packages provided by channels to be used in nix expressions. If a channel installed a valid deriver
for each package it provides into the store, then those could be imported and used as dependencies or installed
in environment.systemPackages, for example.
* Enable hydra to be consistent in how it treats inputs that are outputs of another build. Right now, if an
input is passed as an argument to the job, it is passed as a derivation, but if it is accessed via NIX_PATH
(i.e. through the <> syntax), then it is a path that can be imported. This is problematic because the build
being depended upon may have been built with non-obvious arguments passed to its jobset file. With this
feature, hydra can just set the name of that input to the path to its drv file in NIX_PATH
For each output, this adds a corresponding attribute to the derivation that is
the same as the derivation except for outPath, which is set to the path specific
to that output. Additionally, an "all" attribute is added that is a list of all
of the output derivations. This has to be done outside of derivationStrict as
each output is itself a derivation that contains itself (and all other outputs)
as an attribute. The derivation itself is equivalent to the first output in the
outputs list (or "out" if that list isn't set).
