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Add a command "nix-build --run-env" to reproduce the environment of a…

… derivation

This command builds or fetches all dependencies of the given
derivation, then starts a shell with the environment variables from
the derivation.  This shell also sources $stdenv/setup to initialise
the environment further.

The current directory is not changed.  Thus this is a convenient way
to reproduce a build environment in an existing working tree.

Existing environment variables are left untouched (unless the
derivation overrides them).  As a special hack, the original value of
$PATH is appended to the $PATH produced by $stdenv/setup.

Example session:

$ nix-build --run-env '<nixpkgs>' -A xterm
(the dependencies of xterm are built/fetched...)
$ tar xf $src
$ ./configure
$ make
$ emacs
(... hack source ...)
$ make
$ ./xterm
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1 parent ea402a2 commit 7f38087f35e6f74a73bfdb28da8acd8930565d51 @edolstra edolstra committed Mar 19, 2012
Showing with 72 additions and 0 deletions.
  1. +1 −0 perl/lib/Nix/Store.pm
  2. +42 −0 perl/lib/Nix/Store.xs
  3. +29 −0 scripts/nix-build.in
View
1 perl/lib/Nix/Store.pm
@@ -16,6 +16,7 @@ our @EXPORT = qw(
topoSortPaths computeFSClosure followLinksToStorePath exportPaths
hashPath hashFile hashString
addToStore makeFixedOutputPath
+ derivationFromPath
);
our $VERSION = '0.15';
View
42 perl/lib/Nix/Store.xs
@@ -216,3 +216,45 @@ SV * makeFixedOutputPath(int recursive, char * algo, char * hash, char * name)
} catch (Error & e) {
croak(e.what());
}
+
+
+SV * derivationFromPath(char * drvPath)
+ PREINIT:
+ HV *hash;
+ CODE:
+ try {
+ doInit();
+ Derivation drv = derivationFromPath(*store, drvPath);
+ hash = newHV();
+
+ /* TODO: handle drv.outputs */
+
+ AV * inputDrvs = newAV();
+ for (DerivationInputs::iterator i = drv.inputDrvs.begin(); i != drv.inputDrvs.end(); ++i)
+ av_push(inputDrvs, newSVpv(i->first.c_str(), 0)); // !!! ignores i->second
+ hv_stores(hash, "inputDrvs", newRV((SV *) inputDrvs));
+
+ AV * inputSrcs = newAV();
+ for (PathSet::iterator i = drv.inputSrcs.begin(); i != drv.inputSrcs.end(); ++i)
+ av_push(inputSrcs, newSVpv(i->c_str(), 0));
+ hv_stores(hash, "inputSrcs", newRV((SV *) inputSrcs));
+
+ hv_stores(hash, "platform", newSVpv(drv.platform.c_str(), 0));
+ hv_stores(hash, "builder", newSVpv(drv.builder.c_str(), 0));
+
+ AV * args = newAV();
+ for (Strings::iterator i = drv.args.begin(); i != drv.args.end(); ++i)
+ av_push(args, newSVpv(i->c_str(), 0));
+ hv_stores(hash, "args", newRV((SV *) args));
+
+ HV * env = newHV();
+ for (StringPairs::iterator i = drv.env.begin(); i != drv.env.end(); ++i)
+ hv_store(env, i->first.c_str(), i->first.size(), newSVpv(i->second.c_str(), 0), 0);
+ hv_stores(hash, "env", newRV((SV *) env));
+
+ RETVAL = newRV_noinc((SV *)hash);
+ } catch (Error & e) {
+ croak(e.what());
+ }
+ OUTPUT:
+ RETVAL
View
29 scripts/nix-build.in
@@ -2,11 +2,13 @@
use strict;
use Nix::Config;
+use Nix::Store;
use File::Temp qw(tempdir);
my $dryRun = 0;
my $verbose = 0;
+my $runEnv = 0;
my @instArgs = ();
my @buildArgs = ();
@@ -119,6 +121,10 @@ EOF
push @instArgs, $arg;
}
+ elsif ($arg eq "--run-env") {
+ $runEnv = 1;
+ }
+
elsif (substr($arg, 0, 1) eq "-") {
push @buildArgs, $arg;
}
@@ -143,6 +149,29 @@ foreach my $expr (@exprs) {
exit 1;
}
+ if ($runEnv) {
+ die "$0: ‘--run-env’ requires a single derivation\n" if scalar @drvPaths != 1;
+ my $drvPath = readlink $drvPaths[0] or die "cannot read symlink `$drvPaths[0]'";
+ my $drv = derivationFromPath($drvPath);
+
+ # Build or fetch all dependencies of the derivation.
+ system("$Nix::Config::binDir/nix-store -r @buildArgs @{$drv->{inputDrvs}} @{$drv->{inputSrcs}} > /dev/null") == 0
+ or die "$0: failed to build all dependencies\n";
+
+ # Set the environment.
+ $ENV{'NIX_BUILD_TOP'} = $ENV{'TMPDIR'} || "/tmp";
+ foreach (keys %{$drv->{env}}) {
+ $ENV{$_} = $drv->{env}->{$_};
+ }
+
+ # Run a shell using the derivation's environment. For
+ # convenience, source $stdenv/setup to setup additional
+ # environment variables. Also don't lose the current $PATH
+ # directories.
+ exec($ENV{SHELL}, "-c", "p=\$PATH; source \$stdenv/setup; PATH=\$PATH:\$p; exec $ENV{SHELL}");
+ die;
+ }
+
foreach my $drvPath (@drvPaths) {
my $target = readlink $drvPath or die "cannot read symlink `$drvPath'";
print STDERR "derivation is $target\n" if $verbose;

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