diff options
-rw-r--r-- | doc/functions/overrides.xml | 13 | ||||
-rw-r--r-- | doc/overlays.xml | 191 | ||||
-rw-r--r-- | pkgs/top-level/stage.nix | 15 |
3 files changed, 136 insertions, 83 deletions
diff --git a/doc/functions/overrides.xml b/doc/functions/overrides.xml index 021c4b41c360..1bd90d2a0c76 100644 --- a/doc/functions/overrides.xml +++ b/doc/functions/overrides.xml @@ -6,8 +6,14 @@ <para> Sometimes one wants to override parts of <literal>nixpkgs</literal>, e.g. - derivation attributes, the results of derivations or even the whole package - set. + derivation attributes, the results of derivations. + </para> + + <para> + These functions are used to make changes to packages, returning only single + packages. <link xlink:href="#chap-overlays">Overlays</link>, on the other + hand, can be used to combine the overridden packages across the entire + package set of Nixpkgs. </para> <section xml:id="sec-pkg-override"> @@ -25,6 +31,9 @@ <para> Example usages: <programlisting>pkgs.foo.override { arg1 = val1; arg2 = val2; ... }</programlisting> +<!-- TODO: move below programlisting to a new section about extending and overlays + and reference it + --> <programlisting> import pkgs.path { overlays = [ (self: super: { foo = super.foo.override { barSupport = true ; }; diff --git a/doc/overlays.xml b/doc/overlays.xml index 2decf9febe80..90dd163072d3 100644 --- a/doc/overlays.xml +++ b/doc/overlays.xml @@ -17,91 +17,122 @@ <title>Installing overlays</title> <para> - The list of overlays is determined as follows. + The list of overlays can be set either explicitly in a Nix expression, or + through <literal><nixpkgs-overlays></literal> or user configuration + files. </para> - <para> - If the <varname>overlays</varname> argument is not provided explicitly, we - look for overlays in a path. The path is determined as follows: - <orderedlist> - <listitem> - <para> - First, if an <varname>overlays</varname> argument to the nixpkgs function - itself is given, then that is used. - </para> - <para> - This can be passed explicitly when importing nipxkgs, for example - <literal>import <nixpkgs> { overlays = [ overlay1 overlay2 ]; - }</literal>. - </para> - </listitem> - <listitem> - <para> - Otherwise, if the Nix path entry <literal><nixpkgs-overlays></literal> - exists, we look for overlays at that path, as described below. - </para> - <para> - See the section on <literal>NIX_PATH</literal> in the Nix manual for more - details on how to set a value for - <literal><nixpkgs-overlays>.</literal> - </para> - </listitem> - <listitem> - <para> - If one of <filename>~/.config/nixpkgs/overlays.nix</filename> and - <filename>~/.config/nixpkgs/overlays/</filename> exists, then we look for - overlays at that path, as described below. It is an error if both exist. - </para> - </listitem> - </orderedlist> - </para> + <section xml:id="sec-overlays-argument"> + <title>Set overlays in NixOS or Nix expressions</title> - <para> - If we are looking for overlays at a path, then there are two cases: - <itemizedlist> - <listitem> - <para> - If the path is a file, then the file is imported as a Nix expression and - used as the list of overlays. - </para> - </listitem> - <listitem> - <para> - If the path is a directory, then we take the content of the directory, - order it lexicographically, and attempt to interpret each as an overlay - by: - <itemizedlist> - <listitem> - <para> - Importing the file, if it is a <literal>.nix</literal> file. - </para> - </listitem> - <listitem> - <para> - Importing a top-level <filename>default.nix</filename> file, if it is - a directory. - </para> - </listitem> - </itemizedlist> - </para> - </listitem> - </itemizedlist> - </para> + <para> + On a NixOS system the value of the <literal>nixpkgs.overlays</literal> + option, if present, is passed to the system Nixpkgs directly as an + argument. Note that this does not affect the overlays for non-NixOS + operations (e.g. <literal>nix-env</literal>), which are + <link xlink:href="#sec-overlays-lookup">looked</link> up independently. + </para> - <para> - On a NixOS system the value of the <literal>nixpkgs.overlays</literal> - option, if present, is passed to the system Nixpkgs directly as an argument. - Note that this does not affect the overlays for non-NixOS operations (e.g. - <literal>nix-env</literal>), which are looked up independently. - </para> + <para> + The list of overlays can be passed explicitly when importing nixpkgs, for + example <literal>import <nixpkgs> { overlays = [ overlay1 overlay2 ]; + }</literal>. + </para> - <para> - The <filename>overlays.nix</filename> option therefore provides a convenient - way to use the same overlays for a NixOS system configuration and user - configuration: the same file can be used as - <filename>overlays.nix</filename> and imported as the value of - <literal>nixpkgs.overlays</literal>. - </para> + <para> + Further overlays can be added by calling the <literal>pkgs.extend</literal> + or <literal>pkgs.appendOverlays</literal>, although it is often preferable + to avoid these functions, because they recompute the Nixpkgs fixpoint, + which is somewhat expensive to do. + </para> + </section> + + <section xml:id="sec-overlays-lookup"> + <title>Install overlays via configuration lookup</title> + + <para> + The list of overlays is determined as follows. + </para> + + <para> + <orderedlist> + <listitem> + <para> + First, if an + <link xlink:href="#sec-overlays-argument"><varname>overlays</varname> + argument</link> to the nixpkgs function itself is given, then that is + used and no path lookup will be performed. + </para> + </listitem> + <listitem> + <para> + Otherwise, if the Nix path entry + <literal><nixpkgs-overlays></literal> exists, we look for overlays at + that path, as described below. + </para> + <para> + See the section on <literal>NIX_PATH</literal> in the Nix manual for + more details on how to set a value for + <literal><nixpkgs-overlays>.</literal> + </para> + </listitem> + <listitem> + <para> + If one of <filename>~/.config/nixpkgs/overlays.nix</filename> and + <filename>~/.config/nixpkgs/overlays/</filename> exists, then we look + for overlays at that path, as described below. It is an error if both + exist. + </para> + </listitem> + </orderedlist> + </para> + + <para> + If we are looking for overlays at a path, then there are two cases: + <itemizedlist> + <listitem> + <para> + If the path is a file, then the file is imported as a Nix expression and + used as the list of overlays. + </para> + </listitem> + <listitem> + <para> + If the path is a directory, then we take the content of the directory, + order it lexicographically, and attempt to interpret each as an overlay + by: + <itemizedlist> + <listitem> + <para> + Importing the file, if it is a <literal>.nix</literal> file. + </para> + </listitem> + <listitem> + <para> + Importing a top-level <filename>default.nix</filename> file, if it is + a directory. + </para> + </listitem> + </itemizedlist> + </para> + </listitem> + </itemizedlist> + </para> + + <para> + Because overlays that are set in NixOS configuration do not affect + non-NixOS operations such as <literal>nix-env</literal>, the + <filename>overlays.nix</filename> option provides a convenient way to use + the same overlays for a NixOS system configuration and user configuration: + the same file can be used as <filename>overlays.nix</filename> and imported + as the value of <literal>nixpkgs.overlays</literal>. + </para> + +<!-- TODO: Example of sharing overlays between NixOS configuration + and configuration lookup. Also reference the example + from the sec-overlays-argument paragraph about NixOS. + --> + </section> </section> <!--============================================================--> <section xml:id="sec-overlays-definition"> diff --git a/pkgs/top-level/stage.nix b/pkgs/top-level/stage.nix index d0fb885dc747..37724a870a30 100644 --- a/pkgs/top-level/stage.nix +++ b/pkgs/top-level/stage.nix @@ -56,7 +56,7 @@ , # A list of overlays (Additional `self: super: { .. }` customization # functions) to be fixed together in the produced package set overlays -}: +} @args: let stdenvAdapters = self: super: @@ -159,6 +159,19 @@ let }; }; }; + + # Extend the package set with zero or more overlays. This preserves + # preexisting overlays. Prefer to initialize with the right overlays + # in one go when calling Nixpkgs, for performance and simplicity. + appendOverlays = extraOverlays: + import ./stage.nix (args // { overlays = args.overlays ++ extraOverlays; }); + + # Extend the package set with a single overlay. This preserves + # preexisting overlays. Prefer to initialize with the right overlays + # in one go when calling Nixpkgs, for performance and simplicity. + # Prefer appendOverlays if used repeatedly. + extend = f: self.appendOverlays [f]; + }; # The complete chain of package set builders, applied from top to bottom. |