intersectAttrs returns the (right-biased) intersection between two
attribute sets, e.g. every attribute from the second set that also
exists in the first. functionArgs returns the set of attributes
expected by a function.
The main goal of these is to allow the elimination of most of
all-packages.nix. Most package instantiations in all-packages.nix
have this form:
foo = import ./foo.nix {
inherit a b c;
};
With intersectAttrs and functionArgs, this can be written as:
foo = callPackage (import ./foo.nix) { };
where
callPackage = f: args:
f ((builtins.intersectAttrs (builtins.functionArgs f) pkgs) // args);
I.e., foo.nix is called with all attributes from "pkgs" that it
actually needs (e.g., pkgs.a, pkgs.b and pkgs.c). (callPackage can
do any other generic package-level stuff we might want, such as
applying makeOverridable.) Of course, the automatically supplied
arguments can be overriden if needed, e.g.
foo = callPackage (import ./foo.nix) {
c = c_version_2;
};
but for the vast majority of packages, this won't be needed.
The advantages are to reduce the amount of typing needed to add a
dependency (from three sites to two), and to reduce the number of
trivial commits to all-packages.nix. For the former, there have
been two previous attempts:
- Use "args: with args;" in the package's function definition.
This however obscures the actual expected arguments of a
function, which is very bad.
- Use "{ arg1, arg2, ... }:" in the package's function definition
(i.e. use the ellipis "..." to allow arbitrary additional
arguments), and then call the function with all of "pkgs" as an
argument. But this inhibits error detection if you call it with
an misspelled (or obsolete) argument.
NixOS evaluation errors in particular look intimidating and
generally aren't very useful. Ideally the builtins.throw messages
should be self-contained.
sure that it works as expected when you pass it a derivation. That
is, we have to make sure that all build-time dependencies are built,
and that they are all in the input closure (otherwise remote builds
might fail, for example). This is ensured at instantiation time by
adding all derivations and their sources to inputDrvs and inputSrcs.
derivation should be a source rather than a derivation dependency of
the call to the NAR derivation. Otherwise the derivation (and all
its dependencies) will be built as a side-effect, which may not even
succeed.
SHA-256 outputs of fixed-output derivations. I.e. they now produce
the same store path:
$ nix-store --add x
/nix/store/j2fq9qxvvxgqymvpszhs773ncci45xsj-x
$ nix-store --add-fixed --recursive sha256 x
/nix/store/j2fq9qxvvxgqymvpszhs773ncci45xsj-x
the latter being the same as the path that a derivation
derivation {
name = "x";
outputHashAlgo = "sha256";
outputHashMode = "recursive";
outputHash = "...";
...
};
produces.
This does change the output path for such fixed-output derivations.
Fortunately they are quite rare. The most common use is fetchsvn
calls with SHA-256 hashes. (There are a handful of those is
Nixpkgs, mostly unstable development packages.)
* Documented the computation of store paths (in store-api.cc).
dependency. `storePath /nix/store/bla' gives exactly the same
result as `toPath /nix/store/bla', except that the former includes
/nix/store/bla in the dependency context of the string.
Useful in some generated Nix expressions like nix-push, which now
finally does the right thing wrt distributed builds. (Previously
the path to be packed wasn't an explicit dependency, so it wouldn't
be copied to the remote machine.)
functions that take a single argument (plain lambdas) into one AST
node (Function) that contains a Pattern node describing the
arguments. Current patterns are single lazy arguments (VarPat) and
matching against an attribute set (AttrsPat).
This refactoring allows other kinds of patterns to be added easily,
such as Haskell-style @-patterns, or list pattern matching.
logic through the `parseDrvName' and `compareVersions' primops.
This will allow expressions to easily check whether some dependency
is a specific needed version or falls in some version range. See
tests/lang/eval-okay-versions.nix for examples.
;-)
* Channels: fix channels that are plain lists of derivations (like
strategoxt-unstable) instead of functions (like nixpkgs-unstable).
This fixes the error message "error: the left-hand side of the
function call is neither a function nor a primop (built-in
operation) but a list".
computing the store path (NIX-77). This is an important security
property in multi-user Nix stores.
Note that this changes the store paths of derivations (since the
derivation aterms are added using addTextToStore), but not most
outputs (unless they use builtins.toFile).
* `sub' to subtract two numbers.
* `stringLength' to get the length of a string.
* `substring' to get a substring of a string. These should be enough
to allow most string operations to be expressed.
from a source directory. All files for which a predicate function
returns true are copied to the store. Typical example is to leave
out the .svn directory:
stdenv.mkDerivation {
...
src = builtins.filterSource
(path: baseNameOf (toString path) != ".svn")
./source-dir;
# as opposed to
# src = ./source-dir;
}
This is important because the .svn directory influences the hash in
a rather unpredictable and variable way.
containing functions that operate on the Nix store. One
implementation is LocalStore, which operates on the Nix store
directly. The next step, to enable secure multi-user Nix, is to
create a different implementation RemoteStore that talks to a
privileged daemon process that uses LocalStore to perform the actual
operations.
concatenation and string coercion. This was a big mess (see
e.g. NIX-67). Contexts are now folded into strings, so that they
don't cause evaluation errors when they're not expected. The
semantics of paths has been clarified (see nixexpr-ast.def).
toString() and coerceToString() have been merged.
Semantic change: paths are now copied to the store when they're in a
concatenation (and in most other situations - that's the
formalisation of the meaning of a path). So
"foo " + ./bla
evaluates to "foo /nix/store/hash...-bla", not "foo
/path/to/current-dir/bla". This prevents accidental impurities, and
is more consistent with the treatment of derivation outputs, e.g.,
`"foo " + bla' where `bla' is a derivation. (Here `bla' would be
replaced by the output path of `bla'.)
side should be a path, I guess.
* Handle paths that are in the store but not direct children of the
store directory.
* Ugh, hack to prevent double context wrapping.
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 ...'.
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.
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.
`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).
derivations. This is mostly to simplify the implementation of
nix-prefetch-{url, svn}, which now work properly in setuid
installations.
* Enforce valid store names in `nix-store --add / --add-fixed'.
* Set the references for the user environment manifest properly.
* Don't copy the manifest (this was accidental).
* Don't store derivation paths in the manifest (maybe this should be
made optional). This cleans up the semantics of nix-env, which were
weird.
* Hash on the output paths of activated components, not on derivation
paths. This is because we don't know the derivation path of already
installed components anymore, and it allows the installation of
components by store path (skipping Nix expressions entirely).
* Query options `--out-path' and `--drv-path' to show the output and
derivation paths of components, respectively (the latter replaces
the `--expr' query).
promise :-) This allows derivations to specify on *what* output
paths of input derivations they are dependent. This helps to
prevent unnecessary downloads. For instance, a build might be
dependent on the `devel' and `lib' outputs of some library
component, but not the `docs' output.
