From e7eba9cc46547ae86642ad3c6a9a4fb22c07bc26 Mon Sep 17 00:00:00 2001
From: Kamal Al Marhubi <kamal@marhubi.com>
Date: Tue, 29 Nov 2022 16:26:00 -0500
Subject: [PATCH] home-manager: refine flake URI lookup

Depending on DHCP settings you might end up with different output from
running `hostname`. Eg, your local hostname is `mylaptop`, and your
home router is configured with a local domain of `.hoome.arpa`. In
this case:

    $ hostname
    mylaptop.home.arpa
    $ hostname -s
    mylaptop

If you then go to cafe which has its router configured with `.lan` as
its local domain. Then, if your DHCP settings accept the local domain
from the router,

    $ hostname
    myalaptop.lan
    $ hostname -s
    mylaptop

With the pre-existing behaviour, if you had a
`"me@mylaptop.home.arpa"` entry in `outputs.homeConfigurations`,
running `home-manager switch` would fail:

    $ home-manager switch
    error: flake 'git+file:///home/me/.config/nixpkgs' does not provide
    attribute 'packages.aarch64-darwin.homeConfigurations."me".activationPackage',
    'legacyPackages.aarch64-darwin.homeConfigurations."me".activationPackage'
    or 'homeConfigurations."me".activationPackage'

After this commit, you can put configuration in a `"me@mylaptop"`
entry in `outputs.homeConfigurations`, and everything will work on
either network.
---
 home-manager/home-manager | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/home-manager/home-manager b/home-manager/home-manager
index 9a5af6d93..459908f2e 100644
--- a/home-manager/home-manager
+++ b/home-manager/home-manager
@@ -106,10 +106,17 @@ function setFlakeAttribute() {
                 local name="${FLAKE_ARG#*#}"
             ;;
             *)
-                local name="$USER@$(hostname)"
-                if [ "$(nix eval "$flake#homeConfigurations" --apply "x: x ? \"$name\"")" = "false" ]; then
-                    name="$USER"
-                fi
+                local name="$USER"
+                # Check both long and short hostnames; long first to preserve
+                # pre-existing behaviour in case both happen to be defined.
+                for n in "$USER@$(hostname)" "$USER@$(hostname -s)"; do
+                    if [[ "$(nix eval "$flake#homeConfigurations" --apply "x: x ? \"$n\"")" == "true" ]]; then
+                        name="$n"
+                        if [[ -v VERBOSE ]]; then
+                            echo "Using flake homeConfiguration for $name"
+                        fi
+                    fi
+                done
             ;;
         esac
         export FLAKE_CONFIG_URI="$flake#homeConfigurations.\"$name\""