Update a package: Difference between revisions

mkdir ~/devel/

cd ~/devel/

cd nixpkgs/

git remote add upstream https://github.com/NixOS/nixpkgs.git</syntaxhighlight>

== Following the white rabbit ==

* I will center this tutorial on the nix expression that packages the [http://i3wm.org/ i3 window manager], as this expression is quite simple and it was contributing to this expression that I got to understand this whole workflow I am documenting.

* In <tt>~/devel/nixpkgs/default.nix</tt> there is an ''import'' statement that reads <tt>import ./pkgs/top-level/all-packages.nix</tt>

* We will dive (not too deep, though) on <tt>pkgs/applications/window-managers/i3/default.nix</tt> which is the nix expression that corresponds to the package for the i3 window manager:

<syntaxhighlight lang="nix">

   xcbutilwm, libstartup_notification, libX11, pcre, libev, yajl,

   libXcursor, coreutils, perl, pango }:

   };

     libstartup_notification libX11 pcre libev yajl libXcursor perl pango ];

     patchShebangs

   '';

** Changed the <tt>version</tt> string.

** Changed the checksum for the tarball on the <tt>sha256</tt> string.

* And in an attempt to extract something positive from the issue, we are going to review an additional [https://github.com/NixOS/nixpkgs/commit/1eb437784021521d57ae96980bf447e9162d4415 unfortunate change] I made on <tt>pkgs/top-level/all-packages.nix</tt>

* To figure out the checksum for the tarball you have the <tt>nix-prefetch-url</tt> utility. In addition to returning the ''sha256 checksum'' it will also leave the downloaded blob on your ''nix store'', thus avoiding additional downloads when you test the build process. You get the path to the downloaded blob and the ''sha256sum'' on the last two lines of the command's output:

+++ b/pkgs/applications/window-managers/i3/default.nix

@@ -1,21 +1,20 @@

   xcbutilwm, libstartup_notification, libX11, pcre, libev, yajl,

-  libXcursor, coreutils, perl }:

   };

   

-    libstartup_notification libX11 pcre libev yajl libXcursor perl ];

+    libstartup_notification libX11 pcre libev yajl libXcursor perl pango ];

   

-    sed -i -e '/^# Pango/,/^$/d' common.mk

     patchShebangs .

* If your current directory is, as we said, <tt>~/devel/nixpkgs/</tt>, you can request nix to build the modified package (see <tt>man nix-build</tt>):

<pre>nix-build -A i3</pre>

* Here I would have detected the error I introduced on <tt>pkgs/top-level/all-packages.nix</tt>. Too bad I didn't still know how to test my changes:

<syntaxhighlight lang="console">

* When the build succeeds, <tt>nix-build</tt> will leave the result linked as <tt>./result</tt> on the current working directory:

<syntaxhighlight lang="console">

   File: "./result" -> "/nix/store/agld76p9rgvn3j610z8kgppz67f8kmg7-i3-4.5.1"

</syntaxhighlight>

+++ b/pkgs/applications/window-managers/i3/default.nix

@@ -1,21 +1,20 @@

   xcbutilwm, libstartup_notification, libX11, pcre, libev, yajl,

-  libXcursor, coreutils, perl }:

   };

   

-    libstartup_notification libX11 pcre libev yajl libXcursor perl ];

+    libstartup_notification libX11 pcre libev yajl libXcursor perl pango ];

   

-    sed -i -e '/^# Pango/,/^$/d' common.mk

     patchShebangs .

+++ b/pkgs/applications/window-managers/i3/default.nix

@@ -1,21 +1,20 @@

   xcbutilwm, libstartup_notification, libX11, pcre, libev, yajl,

-  libXcursor, coreutils, perl }:

   };

   

-    libstartup_notification libX11 pcre libev yajl libXcursor perl ];

+    libstartup_notification libX11 pcre libev yajl libXcursor perl pango ];

   

-    sed -i -e '/^# Pango/,/^$/d' common.mk

     patchShebangs .

Split into 5 hunks.

@@ -1,6 +1,6 @@

   xcbutilwm, libstartup_notification, libX11, pcre, libev, yajl,

-  libXcursor, coreutils, perl }:

   };

   

Stage this hunk [y,n,q,a,d,/,K,j,J,g,e,?]? n

@@ -12,6 +12,6 @@

   };

   

-    libstartup_notification libX11 pcre libev yajl libXcursor perl ];

+    libstartup_notification libX11 pcre libev yajl libXcursor perl pango ];

   

Stage this hunk [y,n,q,a,d,/,K,j,J,g,e,?]? y

@@ -16,6 +16,5 @@

   

-    sed -i -e '/^# Pango/,/^$/d' common.mk

     patchShebangs .

   };

   

</syntaxhighlight>

* As these changes are both related, we can issue a simple commit:

* Now there are 3 commits on the <tt>example</tt> branch of out nixpkgs repository at GitHub.

* The idea is to propose the official ''NixOS/nixpkgs'' maintainers to include our changes on the official repository, so all the ''nixpkgs'' users can eventually benefit of our improvements.

* So now we have to formally ''request'' them to ''pull'' our changes, from our branch to the appropriate branch in ''NixOS/nixpkgs''. Hence the name "''pull request''" which I don't feel so intuitive.

* There is a "Pull Request" button in GitHub. Push it. Go ahead.

* [[Create and debug nix packages]]

* [[Generic Algorithm on Doing Packaging]]