public/nixpkgs
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Add overlays mechanism to Nixpkgs.

Browse Source 
This patch add a new argument to Nixpkgs default expression named "overlays".

By default, the value of the argument is either taken from the environment variable `NIXPKGS_OVERLAYS`,
or from the directory `~/.nixpkgs/overlays/`.  If the environment variable does not name a valid directory
then this mechanism would fallback on the home directory.  If the home directory does not exists it will
fallback on an empty list of overlays.

The overlays directory should contain the list of extra Nixpkgs stages which would be used to extend the
content of Nixpkgs, with additional set of packages.  The overlays, i-e directory, files, symbolic links
are used in alphabetical order.

The simplest overlay which extends Nixpkgs with nothing looks like:

```nix
self: super: {
}
```

More refined overlays can use `super` as the basis for building new packages, and `self` as a way to query
the final result of the fix-point.

An example of overlay which extends Nixpkgs with a small set of packages can be found at:
  https://github.com/nbp/nixpkgs-mozilla/blob/nixpkgs-overlay/moz-overlay.nix

To use this file, checkout the repository and add a symbolic link to
the `moz-overlay.nix` file in `~/.nixpkgs/overlays` directory.
This commit is contained in:
Nicolas B. Pierron
2017-01-16 01:17:33 +01:00
committed by Nicolas B. Pierron
parent 7c8d3aa21d
commit f5dfe78a1e
15 changed files with 160 additions and 103 deletions
Download Patch File Download Diff File Expand all files Collapse all files
doc/functions.xml
+2 -62
View File
@@ -17,66 +17,6 @@
derivations or even the whole package set.
</para>
<section xml:id="sec-pkgs-overridePackages">
<title>pkgs.overridePackages</title>
<para>
This function inside the nixpkgs expression (<varname>pkgs</varname>)
can be used to override the set of packages itself.
</para>
<para>
Warning: this function is expensive and must not be used from within
the nixpkgs repository.
</para>
<para>
Example usage:
<programlisting>let
pkgs = import &lt;nixpkgs&gt; {};
newpkgs = pkgs.overridePackages (self: super: {
foo = super.foo.override { ... };
});
in ...</programlisting>
</para>
<para>
The resulting <varname>newpkgs</varname> will have the new <varname>foo</varname>
expression, and all other expressions depending on <varname>foo</varname> will also
use the new <varname>foo</varname> expression.
</para>
<para>
The behavior of this function is similar to <link
linkend="sec-modify-via-packageOverrides">config.packageOverrides</link>.
</para>
<para>
The <varname>self</varname> parameter refers to the final package set with the
applied overrides. Using this parameter may lead to infinite recursion if not
used consciously.
</para>
<para>
The <varname>super</varname> parameter refers to the old package set.
It's equivalent to <varname>pkgs</varname> in the above example.
</para>
<para>
Note that in previous versions of nixpkgs, this method replaced any changes from <link
linkend="sec-modify-via-packageOverrides">config.packageOverrides</link>,
along with that from previous calls if this function was called repeatedly.
Now those previous changes will be preserved so this function can be "chained" meaningfully.
To recover the old behavior, make sure <varname>config.packageOverrides</varname> is unset,
and call this only once off a "freshly" imported nixpkgs:
<programlisting>let
pkgs = import &lt;nixpkgs&gt; { config: {}; };
newpkgs = pkgs.overridePackages ...;
in ...</programlisting>
</para>
</section>
<section xml:id="sec-pkg-override">
<title>&lt;pkg&gt;.override</title>
@@ -91,9 +31,9 @@
Example usages:
<programlisting>pkgs.foo.override { arg1 = val1; arg2 = val2; ... }</programlisting>
<programlisting>pkgs.overridePackages (self: super: {
<programlisting>import pkgs.path { overlays = [ (self: super: {
foo = super.foo.override { barSupport = true ; };
})</programlisting>
})]};</programlisting>
<programlisting>mypkg = pkgs.callPackage ./mypkg.nix {
mydep = pkgs.mydep.override { ... };
}</programlisting>