Table of Contents

Upgrading old packages

There are many programs that become unmaintained due to whatever reason. This causes downstream builds like nixpkgs to fail. As other programs progress and evolve, attrition rate increases. In most operating systems, old programs are entirely removed and become unsupported.

One of the ways to support old programs in modern systems like NixOS is to contribute to upstream packages or create a patch in nixpkgs.

Here are three ways you can implement patches in nixpkgs.

Add a local patch file

Add a local patch like NixOS/nixpkgs PR#1863491 if the package can’t be built specifically on NixOS.

Find and replace code with substituteInPlace

# https://github.com/NixOS/nixpkgs/blob/4275fc290aaecb6072abcdfc75741373ecfa0fdc/pkgs/tools/misc/xflux/gui.nix#L31C3-L33C12
postPatch = ''
     substituteInPlace src/fluxgui/xfluxcontroller.py \
       --replace "pexpect.spawn(\"xflux\"" "pexpect.spawn(\"${xflux}/bin/xflux\""
  '';

This is usually used when you want to replace file paths across many files in the nix store. Mic92, NixOS release manager, explains it best here.

Submit patch upstream and pull to nixpkgs

torproject/stem

stem package has discussions about project maintenance and it doesn’t seem to have a conclusion yet. What we do know is, the build breaks on hydra CI and it breaks other packages that depends on it, like torrequest.

How do we understand more about the failure? We can run nix build to see the output error messages.

$ nix-build -A python312Packages.stem
...
======================================================================
ERROR: test_index_malformed_compression
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/private/tmp/nix-build-python3.12-stem-1.8.3-unstable-2024-02-13.drv-0/source/test/unit/descriptor/collector.py", line 126, in test_index_malformed_compression
    self.assertRaisesRegexp(OSError, 'Failed to decompress as %s' % compression, collector.index, compression)
    ^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: '_TestWrapper' object has no attribute 'assertRaisesRegexp'. Did you mean: 'assertRaisesRegex'?

====

After investigating, it is revealed Python3 has deprecated assertRaisesRegexp in its unittest library. But torproject/stem supports both Python2 and 3.

In this case, we should make a PR contribution to torproject/stem (see PR#155). We replace all instances of assertRaisesRegexp with assertRaisesRegex and add this check to support Python2.

# Allow test cases to run on both Python2 and Python3
if not hasattr(TestCase, 'assertRaisesRegex'):
    TestCase.assertRaisesRegex = TestCase.assertRaisesRegexp

Then in default.nix, you can use fetchpatch attribute to fetch from remote repository into nix build.

  patches = [
    # fixes deprecated test assertion, assertRaisesRegexp in python 3
    (fetchpatch {
      url = "https://github.com/trishtzy/stem/commit/d5012a1039f05c69ebe832723ce96ecbe8f79fe1.patch";
      hash = "sha256-ozOTx4/c86sW/9Ss5eZ6ZxX63ByJT5x7JF6wBBd+VFY=";
    })
  ];

From NixOS/nixpkgs PR#311118

Run nix build again.

$ nix-build -A python312Packages.stem
...
Executing pythonImportsCheckPhase
/nix/store/3qk6z4zfp1n62qmsf1h09shs91f95bjg-python3.12-stem-1.8.3-unstable-2024-02-13

The build suceeds! And now, in a newer hydra evaluation, you’ll be able to see python312Packages.stem.* is newly succeeded. Even better, any packages depending on stem that failed, like torrequest build, succeeds too.2

Footnotes

  1. You should read the linked issue #186294 for context ↩

  2. A big thanks to @RaghavSood who gave guidance on this nixpkg contribution and the previous too. ↩