Skip to content

Commit

Permalink
mkDerivation: add overrideAttrs function
Browse files Browse the repository at this point in the history
This is similar to `overrideDerivation`, but overrides the arguments to
`mkDerivation` instead of the underlying `derivation` call.

Also update `makeOverridable` so that uses of `overrideAttrs` can be
followed by `override` and `overrideDerivation`, i.e. they can be
mix-and-matched.
  • Loading branch information
aneeshusa committed Oct 2, 2016
1 parent fbcb938 commit 39b64b5
Show file tree
Hide file tree
Showing 3 changed files with 74 additions and 10 deletions.
61 changes: 61 additions & 0 deletions doc/functions.xml
Original file line number Diff line number Diff line change
Expand Up @@ -85,9 +85,70 @@ in ...</programlisting>

</section>

<section xml:id="sec-pkg-overrideAttrs">
<title>&lt;pkg&gt;.overrideAttrs</title>

<para>
The function <varname>overrideAttrs</varname> allows overriding the
attribute set passed to a <varname>stdenv.mkDerivation</varname> call,
producing a new derivation based on the original one.
This function is available on all derivations produced by the
<varname>stdenv.mkDerivation</varname> function, which is most packages
in the nixpkgs expression <varname>pkgs</varname>.
</para>

<para>
Example usage:

<programlisting>helloWithDebug = pkgs.hello.overrideAttrs (oldAttrs: rec {
separateDebugInfo = true;
});</programlisting>
</para>

<para>
In the above example, the <varname>separateDebugInfo</varname> attribute is
overriden to be true, thus building debug info for
<varname>helloWithDebug</varname>, while all other attributes will be
retained from the original <varname>hello</varname> package.
</para>

<para>
The argument <varname>oldAttrs</varname> is conventionally used to refer to
the attr set originally passed to <varname>stdenv.mkDerivation</varname>.
</para>

<note>
<para>
Note that <varname>separateDebugInfo</varname> is processed only by the
<varname>stdenv.mkDerivation</varname> function, not the generated, raw
Nix derivation. Thus, using <varname>overrideDerivation</varname> will
not work in this case, as it overrides only the attributes of the final
derivation. It is for this reason that <varname>overrideAttrs</varname>
should be preferred in (almost) all cases to
<varname>overrideDerivation</varname>, i.e. to allow using
<varname>sdenv.mkDerivation</varname> to process input arguments, as well
as the fact that it is easier to use (you can use the same attribute
names you see in your Nix code, instead of the ones generated (e.g.
<varname>buildInputs</varname> vs <varname>nativeBuildInputs</varname>,
and involves less typing.
</para>
</note>

</section>


<section xml:id="sec-pkg-overrideDerivation">
<title>&lt;pkg&gt;.overrideDerivation</title>

<warning>
<para>You should prefer <varname>overrideAttrs</varname> in almost all
cases, see its documentation for the reasons why.
<varname>overrideDerivation</varname> is not deprecated and will continue
to work, but is less nice to use and does not have as many abilities as
<varname>overrideAttrs</varname>.
</para>
</warning>

<warning>
<para>Do not use this function in Nixpkgs as it evaluates a Derivation
before modifying it, which breaks package abstraction and removes
Expand Down
22 changes: 12 additions & 10 deletions lib/customisation.nix
Original file line number Diff line number Diff line change
Expand Up @@ -56,16 +56,18 @@ rec {
ff = f origArgs;
overrideWith = newArgs: origArgs // (if builtins.isFunction newArgs then newArgs origArgs else newArgs);
in
if builtins.isAttrs ff then (ff //
{ override = newArgs: makeOverridable f (overrideWith newArgs);
overrideDerivation = fdrv:
makeOverridable (args: overrideDerivation (f args) fdrv) origArgs;
})
else if builtins.isFunction ff then
{ override = newArgs: makeOverridable f (overrideWith newArgs);
__functor = self: ff;
overrideDerivation = throw "overrideDerivation not yet supported for functors";
}
if builtins.isAttrs ff then (ff // {
override = newArgs: makeOverridable f (overrideWith newArgs);
overrideDerivation = fdrv:
makeOverridable (args: overrideDerivation (f args) fdrv) origArgs;
${if ff ? overrideAttrs then "overrideAttrs" else null} = fdrv:
makeOverridable (args: (f args).overrideAttrs fdrv) origArgs;
})
else if builtins.isFunction ff then {
override = newArgs: makeOverridable f (overrideWith newArgs);
__functor = self: ff;
overrideDerivation = throw "overrideDerivation not yet supported for functors";
}
else ff;


Expand Down
1 change: 1 addition & 0 deletions pkgs/stdenv/generic/default.nix
Original file line number Diff line number Diff line change
Expand Up @@ -227,6 +227,7 @@ let
outputs = outputs';
} else { })))) (
{
overrideAttrs = f: mkDerivation (attrs // (f attrs));
# The meta attribute is passed in the resulting attribute set,
# but it's not part of the actual derivation, i.e., it's not
# passed to the builder and is not a dependency. But since we
Expand Down

0 comments on commit 39b64b5

Please sign in to comment.