attribute existence and to return an attribute from an attribute
set, respectively. Example: `hasAttr "foo" {foo = 1;}'. They
differ from the `?' and `.' operators in that the attribute name is
an arbitrary expression. (NIX-61)
and returns its path. This can be used to (for instance) write
builders inside a Nix expression, e.g.,
stdenv.mkDerivation {
builder = "
source $stdenv/setup
...
";
...
}
derivation attributes to flatten them into strings. This is
possible since string can nowadays be wrapped in contexts that
describe the derivations/sources referenced by the evaluation of the
string.
all the primops. This allows Nix expressions to test for new
primops and take appropriate action if they're not available. For
instance, rather than calling a primop `foo' directly, they could
say `if builtins ? foo then builtins.foo ... else ...'.
https://svn.cs.uu.nl:12443/repos/trace/buildfarm-control/trunk/ext/nix/,
with some modifications. This allows `nix-env -qa' to show the
attribute path that can be used to unambiguously install a package
using `nix-env -i -A'. Example:
$ nix-env -f top-level/all-packages.nix -qaA subversion xorg-server
subversionWithJava subversion-1.2.3
subversion subversion-1.3.2
subversion14 subversion-1.4.0pre-rc1
xorg.xorgserver xorg-server-1.1.0
argument has a valid value, i.e., is in a certain domain. E.g.,
{ foo : [true false]
, bar : ["a" "b" "c"]
}: ...
This previously could be done using assertions, but domain checks
will allow the buildfarm to automatically extract the configuration
space from functions.
"--with-freetype2-library=" + freetype + "/lib"
can now be written as
"--with-freetype2-library=${freetype}/lib"
An arbitrary expression can be enclosed within ${...}, not just
identifiers.
* Escaping in string literals: \n, \r, \t interpreted as in C, any
other character following \ is interpreted as-is.
* Newlines are now allowed in string literals.
packages (provided that they have a `meta.description' attribute).
E.g.,
$ ./src/nix-env/nix-env -qa --description gcc
gcc-4.0.2 GNU Compiler Collection, 4.0.x (cross-compiler for sparc-linux)
gcc-4.0.2 GNU Compiler Collection, 4.0.x (cross-compiler for mips-linux)
gcc-4.0.2 GNU Compiler Collection, 4.0.x (cross-compiler for arm-linux)
gcc-4.0.2 GNU Compiler Collection, 4.0.x
instantiation, e.g. "nix-env -i" and "nix-env -qas" (but not
"nix-env -qa"). It turns out that many redundant calls to
addToStore(path) were made, which reads and hashes the entire path.
For instance, the bash bootstrap binary in Nixpkgs would be read and
hashed many times. As a result nix-env would spend around 92% of
its time in the function sha256_block (according to callgrind).
Some simple memoization fixes this.
expressions that cause an assertion failure (like `assert system ==
"i686-linux"'). This allows all-packages.nix in Nixpkgs to be used
on all platforms, even if some Nix expressions don't work on all
platforms.
Not sure if this is a good idea; it's a bit hacky. In particular,
due to laziness some derivations might appear in `nix-env -qa' but
disappear in `nix-env -qas' or `nix-env -i'.
Commit 5000!
derivation(s) we're interested, e.g.,
$ nix-instantiate ./all-packages.nix --attr xlibs.libX11
List elements can also be selected:
$ nix-instantiate ./build-for-release.nix --attr 0.subversion
This allows a non-ambiguous specification of a derivation. Of
course, this should also be added to nix-env and nix-build.
dependencyClosure { ... searchPath = [ ../foo ../bar ]; ... }
* Primop `dirOf' to return the directory part of a path (e.g., dirOf
/a/b/c == /a/b).
* Primop `relativise' (according to Webster that's a real word!) that
given paths A and B returns a string representing path B relative
path to A; e.g., relativise /a/b/c a/b/x/y => "../x/y".
determination (e.g., finding the header files dependencies of a C
file) in Nix low-level builds automatically.
For instance, in the function `compileC' in make/lib/default.nix, we
find the header file dependencies of C file `main' as follows:
localIncludes =
dependencyClosure {
scanner = file:
import (findIncludes {
inherit file;
});
startSet = [main];
};
The function works by "growing" the set of dependencies, starting
with the set `startSet', and calling the function `scanner' for each
file to get its dependencies (which should yield a list of strings
representing relative paths). For instance, when `scanner' is
called on a file `foo.c' that includes the line
#include "../bar/fnord.h"
then `scanner' should yield ["../bar/fnord.h"]. This list of
dependencies is absolutised relative to the including file and added
to the set of dependencies. The process continues until no more
dependencies are found (hence its a closure).
`dependencyClosure' yields a list that contains in alternation a
dependency, and its relative path to the directory of the start
file, e.g.,
[ /bla/bla/foo.c
"foo.c"
/bla/bar/fnord.h
"../bar/fnord.h"
]
These relative paths are necessary for the builder that compiles
foo.c to reconstruct the relative directory structure expected by
foo.c.
The advantage of `dependencyClosure' over the old approach (using
the impure `__currentTime') is that it's completely pure, and more
efficient because it only rescans for dependencies (i.e., by
building the derivations yielded by `scanner') if sources have
actually changed. The old approach rescanned every time.
(closed(closed(closed(...)))) since this reduces performance by
producing bigger terms and killing caching (which incidentally also
prevents useful infinite recursion detection).
`removeAttrs attrs ["x", "y"]' returns the set `attrs' with the
attributes named `x' and `y' removed. It is not an error for the
named attributes to be missing from the input set.
* Make the `derivation' primitive much more lazy. The expression
`derivation attrs' now evaluates to (essentially)
attrs // {
type = "derivation";
outPath = derivation! attrs;
drvPath = derivation! attrs;
}
where `derivation!' is a primop that does the actual derivation
instantiation (i.e., it does what `derivation' used to do). The
advantage is that it allows commands such as `nix-env -qa' and
`nix-env -i' to be much faster since they no longer need to
instantiate all derivations, just the `name' attribute. (However,
`nix-env' doesn't yet take advantage of this since it still always
evaluates the `outPath' and `drvPath' attributes).
Also, this allows derivations to cyclically reference each other,
for example,
webServer = derivation {
...
hostName = "svn.cs.uu.nl";
services = [svnService];
};
svnService = derivation {
...
hostName = webServer.hostName;
};
Previously, this would yield a black hole (infinite recursion).
