Overlays - Revision history

DavidFair: Add an example for overriding Perl packages, since the other languages have examples of special cases. This also helps make a definitive version that can be updated (going forward) for people coming from search engines too, rather than forum posts...etc. from years ago.

2026-02-16T12:35:15Z

Add an example for overriding Perl packages, since the other languages have examples of special cases. This also helps make a definitive version that can be updated (going forward) for people coming from search engines too, rather than forum posts...etc. from years ago.

@@ Line 283: / Line 283: @@
        };
      };
 </syntaxhighlight>

Mdaniels5757: clarify

2026-01-05T23:02:39Z

clarify

← Older revision		Revision as of 23:02, 5 January 2026
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	As you can see, <tt>final</tt> is the same for every stage, but <tt>prev</tt> comes from only the stage before. So when you define an attribute <tt>foo</tt> in the set to override it, within that overlay <tt>final.foo</tt> will be its version, and <tt>prev.foo</tt> will be the non-overriden version. This is why you see patterns like <tt>foo = prev.foo.override { ... }</tt>.		As you can see, <tt>final</tt> is the same for every stage, but <tt>prev</tt> comes from only the stage before. So when you define an attribute <tt>foo</tt> in the set to override it, within that overlay <tt>final.foo</tt> will be its version, and <tt>prev.foo</tt> will be the non-overriden version. This is why you see patterns like <tt>foo = prev.foo.override { ... }</tt>.

	The alternate names <tt>self</tt> and <tt>super</tt> might remind you of inheritance in object-oriented languages. In fact, overlays are exactly the same thing as subclasses, with regards to overriding and calling methods. This data flow is also how objects know which method to call. This is probably how the two arguments got ~~their~~ names, too.		The alternate names <tt>self</tt> and <tt>super</tt> might remind you of inheritance in object-oriented languages. In fact, overlays are exactly the same thing as subclasses, with regards to overriding and calling methods. This data flow is also how objects know which method to call. This is probably how the two arguments got those names, too.

	== Data flow of overlays (alternative explanation) ==		== Data flow of overlays (alternative explanation) ==

Mdaniels5757: /* Data flow of overlays */ change the bit about the names of the arguments being similar to subclassing to correctly refer to self and super instead of final and prev

2026-01-05T22:58:09Z

Data flow of overlays: change the bit about the names of the arguments being similar to subclassing to correctly refer to self and super instead of final and prev

← Older revision		Revision as of 22:58, 5 January 2026
Line 26:		Line 26:
	As you can see, <tt>final</tt> is the same for every stage, but <tt>prev</tt> comes from only the stage before. So when you define an attribute <tt>foo</tt> in the set to override it, within that overlay <tt>final.foo</tt> will be its version, and <tt>prev.foo</tt> will be the non-overriden version. This is why you see patterns like <tt>foo = prev.foo.override { ... }</tt>.		As you can see, <tt>final</tt> is the same for every stage, but <tt>prev</tt> comes from only the stage before. So when you define an attribute <tt>foo</tt> in the set to override it, within that overlay <tt>final.foo</tt> will be its version, and <tt>prev.foo</tt> will be the non-overriden version. This is why you see patterns like <tt>foo = prev.foo.override { ... }</tt>.

	The names <tt>~~final~~</tt> and <tt>~~prev~~</tt> might remind you of inheritance in object-oriented languages. In fact, overlays are exactly the same thing as subclasses, with regards to overriding and calling methods. This data flow is also how objects know which method to call. This is probably how the two arguments got their names, too.		The alternate names <tt>self</tt> and <tt>super</tt> might remind you of inheritance in object-oriented languages. In fact, overlays are exactly the same thing as subclasses, with regards to overriding and calling methods. This data flow is also how objects know which method to call. This is probably how the two arguments got their names, too.

	== Data flow of overlays (alternative explanation) ==		== Data flow of overlays (alternative explanation) ==

Tfc: Add another link to a comprehensive nixpkgs overlays article

2025-11-07T17:53:34Z

Add another link to a comprehensive nixpkgs overlays article

← Older revision		Revision as of 17:53, 7 November 2025
Line 402:		Line 402:

	* [https://nixos.org/nixpkgs/manual/#chap-overlays Overlays in nixpkgs manual]		* [https://nixos.org/nixpkgs/manual/#chap-overlays Overlays in nixpkgs manual]
			* [https://nixcademy.com/posts/mastering-nixpkgs-overlays-techniques-and-best-practice/ Blog post "Mastering Nixpkgs Overlays: Techniques and Best Practice"]
	* [https://blog.flyingcircus.io/2017/11/07/nixos-the-dos-and-donts-of-nixpkgs-overlays/ Blog post "The DOs and DON’Ts of nixpkgs overlays"]		* [https://blog.flyingcircus.io/2017/11/07/nixos-the-dos-and-donts-of-nixpkgs-overlays/ Blog post "The DOs and DON’Ts of nixpkgs overlays"]
	* [https://www.youtube.com/watch?v=s2fkgkN55vk&list=PLgknCdxP89ReD6gxl755B6G_CI65z4J2e Nixpkgs Overlays – A place for all excluded packages] - Talk by Nicolas B. Pierron at NixCon 2017		* [https://www.youtube.com/watch?v=s2fkgkN55vk&list=PLgknCdxP89ReD6gxl755B6G_CI65z4J2e Nixpkgs Overlays – A place for all excluded packages] - Talk by Nicolas B. Pierron at NixCon 2017

Guttermonk: if the hash type is not included in the hash here, you'll receive the following error: hash does not include a type, nor is the type otherwise known from context

2025-08-07T22:08:47Z

if the hash type is not included in the hash here, you'll receive the following error: hash does not include a type, nor is the type otherwise known from context

← Older revision		Revision as of 22:08, 7 August 2025
Line 182:		Line 182:
	# specified: sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=		# specified: sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
	# got: sha256-173gxk0ymiw94glyjzjizp8bv8g72gwkjhacigd1an09jshdrjb4		# got: sha256-173gxk0ymiw94glyjzjizp8bv8g72gwkjhacigd1an09jshdrjb4
	hash = "173gxk0ymiw94glyjzjizp8bv8g72gwkjhacigd1an09jshdrjb4";		hash = "sha256-173gxk0ymiw94glyjzjizp8bv8g72gwkjhacigd1an09jshdrjb4";
	};		};
	});		});

Cdro: /* Overriding a package inside an extensible attribute set */ Fix formatting

2025-02-18T09:31:34Z

Overriding a package inside an extensible attribute set: Fix formatting

← Older revision		Revision as of 09:31, 18 February 2025
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	=== Overriding a package inside an extensible attribute set ===		=== Overriding a package inside an extensible attribute set ===

	Here is an example of adding plugins to `vimPlugins`.		Here is an example of adding plugins to <code>vimPlugins</code>.
	<syntaxhighlight lang="nix">		<syntaxhighlight lang="nix">
	final: prev: {		final: prev: {

FliegendeWurst: /* See also */ link relevant page in see also

2025-01-12T09:33:27Z

See also: link relevant page in see also

← Older revision		Revision as of 09:33, 12 January 2025
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	* [https://blog.flyingcircus.io/2017/11/07/nixos-the-dos-and-donts-of-nixpkgs-overlays/ Blog post "The DOs and DON’Ts of nixpkgs overlays"]		* [https://blog.flyingcircus.io/2017/11/07/nixos-the-dos-and-donts-of-nixpkgs-overlays/ Blog post "The DOs and DON’Ts of nixpkgs overlays"]
	* [https://www.youtube.com/watch?v=s2fkgkN55vk&list=PLgknCdxP89ReD6gxl755B6G_CI65z4J2e Nixpkgs Overlays – A place for all excluded packages] - Talk by Nicolas B. Pierron at NixCon 2017		* [https://www.youtube.com/watch?v=s2fkgkN55vk&list=PLgknCdxP89ReD6gxl755B6G_CI65z4J2e Nixpkgs Overlays – A place for all excluded packages] - Talk by Nicolas B. Pierron at NixCon 2017
			* [[Nixpkgs/Patching Nixpkgs]]

	==== References ====		==== References ====

Adisbladis: Separate python overlay args from nixpkgs overlay args

2024-07-31T11:06:42Z

Separate python overlay args from nixpkgs overlay args

← Older revision		Revision as of 11:06, 31 July 2024
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	python = prev.python.override {		python = prev.python.override {
	# Careful, we're using a different final and prev here!		# Careful, we're using a different final and prev here!
	packageOverrides = ~~final~~: ~~prev~~: {		packageOverrides = pyfinal: pyprev: {
	my_stuff = ~~prev~~.buildPythonPackage rec {		my_stuff = pyprev.buildPythonPackage rec {
	pname = "pyaes";		pname = "pyaes";
	version = "1.6.0";		version = "1.6.0";
	src = ~~prev~~.fetchPypi {		src = pyprev.fetchPypi {
	inherit pname version;		inherit pname version;
	hash = "0bp9bjqy1n6ij1zb86wz9lqa1dhla8qr1d7w2kxyn7jbj56sbmcw";		hash = "0bp9bjqy1n6ij1zb86wz9lqa1dhla8qr1d7w2kxyn7jbj56sbmcw";

Adisbladis: Remove rec from python overlay section. rec should never ever be used in overlays.

2024-07-31T11:05:15Z

Remove rec from python overlay section. rec should never ever be used in overlays.

← Older revision		Revision as of 11:05, 31 July 2024
Line 295:		Line 295:
	final: prev:		final: prev:
	# Within the overlay we use a recursive set, though I think we can use `final` as well.		# Within the overlay we use a recursive set, though I think we can use `final` as well.
	~~rec~~ {		{
	# nix-shell -p python.pkgs.my_stuff		# nix-shell -p python.pkgs.my_stuff
	python = prev.python.override {		python = prev.python.override {
Line 311:		Line 311:
	};		};
	# nix-shell -p pythonPackages.my_stuff		# nix-shell -p pythonPackages.my_stuff
	pythonPackages = python.pkgs;		pythonPackages = final.python.pkgs;

	# nix-shell -p my_stuff		# nix-shell -p my_stuff
	my_stuff = pythonPackages.buildPythonPackage rec {		my_stuff = final.pythonPackages.buildPythonPackage rec {
	pname = "pyaes";		pname = "pyaes";
	version = "1.6.0";		version = "1.6.0";

Nanotwerp: /* Overriding a package inside a scope */

2024-05-11T10:13:09Z

Overriding a package inside a scope

← Older revision		Revision as of 10:13, 11 May 2024
Line 225:		Line 225:
	final: prev: {		final: prev: {
	# elements of pkgs.gnome must be taken from gfinal and gprev		# elements of pkgs.gnome must be taken from gfinal and gprev
	gnome = prev.gnome.overrideScope' (gfinal: gprev: {		gnome = prev.gnome.overrideScope (gfinal: gprev: {
	mutter = gprev.mutter.overrideAttrs (oldAttrs: {		mutter = gprev.mutter.overrideAttrs (oldAttrs: {
	patches = oldAttrs.patches ++ [		patches = oldAttrs.patches ++ [