home-manager: do not build news when using flake

[polykernel]

Currently, the buildNews and doBuildAttrs are always called
unconditionally even if a flake configuration is specified. This cause
it to always fail prior to the actual build performed by doBuildAttrs
because setConfigFIle can not find the home-manager configuration file.
As a result, an error message specifying no configuration file is shown.

Furthermore, if a user has remnant legacy configuration, the doSwitch and
doBuild functions will effectively build the activationPackage twice, with
the legacy configuration overriding the flake configuration.

A conditional check for FLAKE_CONFIG_URI was added to mitigate this by building
the legacy configuration when no flake configuration is present. There is one
exception which is when a flake configuration exists in the default location, where
the user can not build the legacy configuration as along as the file is present.
However, the tradeoff is acceptable as it matches current behavior when FLAKe_CONFIG_URI
is set for instantiation, and an user is unlikely to simulataneously switch
between the two mechanisms.

An abstract function for building flakes doBuildFlake was created to match
doBuildAttrs for manageing options and build flags.

The --no-write-lock-file flag was removed from the --debug case as it is already
matched previously at the --recreate-lock-file case.

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[berbiche]

I don't have a standalone HM configuration ATM so I trust that it works for you 😄

[SuperSandro2000]

Does this fix the following?

home-manager news
error: infinite recursion encountered

       at $HOME/src/nixpkgs/lib/modules.nix:365:28:

          364|         builtins.addErrorContext (context name)
          365|           (args.${name} or config._module.args.${name})
             |                            ^
          366|       ) (lib.functionArgs f);
(use '--show-trace' to show detailed location information)
$HOME/.nix-profile/bin/home-manager: line 425: /tmp/home-manager-build.M3nPK4D340/news-info.sh: No such file or directory

Also how do I now get news on flakes?

[polykernel]

@SuperSandro2000 I don't think I changed anything relating to the presentNews and buildNews functions, I think the only thing that could have changed is news(which must be built using search paths) isn't built unconditionally if flake is used. The previous behavior was to build the flake activationPackage first, followed by legacy activationPackage then news. Unfortunately, this means it is currently impossible to build news with flakes, however I am working on integrating home-manager.nix with modules.nix somehow so it can be exposed in the root flake.

[SuperSandro2000]

was to build the flake activationPackage first, followed by legacy activationPackage then news.

I might have seen that before already. Always wondered why it takes so much longer.

I am working on integrating home-manager.nix with modules.nix somehow so it can be exposed in the root flake.

If you remember please ping me for testing.

I think my above error was due to a bad overlay which is not obvious at all.