beets: warn on implicit enable default

Before 19.03, programs.beets.enable implicitly followed whether
programs.beets.settings was non-empty. That compatibility branch was
still active for older state versions, but it was silent.

Route the default through the shared state-version helper so legacy
users get a consistent deprecation warning before the implicit
enablement is cleaned up. Add focused tests for the legacy and current
default branches alongside the existing beets coverage.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

modules/programs/beets.nix

@@ -27,9 +27,24 @@ in
     programs.beets = {
       enable = mkOption {
         type = types.bool;
-        default =
-          if lib.versionAtLeast config.home.stateVersion "19.03" then false else cfg.settings != { };
-        defaultText = "false";
+        inherit
+          (lib.hm.deprecations.mkStateVersionOptionDefault {
+            inherit (config.home) stateVersion;
+            since = "19.03";
+            optionPath = [
+              "programs"
+              "beets"
+              "enable"
+            ];
+            legacy = {
+              value = cfg.settings != { };
+              text = "config.programs.beets.settings != { }";
+            };
+            current.value = false;
+          })
+          default
+          defaultText
+          ;
         description = ''
           Whether to enable the beets music library manager. This
           defaults to `false` for state

tests/modules/programs/beets/current-disable-default.nix

@@ -0,0 +1,11 @@
+{
+  home.stateVersion = "19.03";
+
+  programs.beets.settings = {
+    directory = "~/Music";
+  };
+
+  nmt.script = ''
+    assertPathNotExists home-files/.config/beets/config.yaml
+  '';
+}

tests/modules/programs/beets/default.nix

@@ -1,5 +1,7 @@
 { lib, pkgs, ... }:
 lib.optionalAttrs pkgs.stdenv.hostPlatform.isLinux {
+  beets-current-disable-default = ./current-disable-default.nix;
+  beets-legacy-enable-default = ./legacy-enable-default.nix;
   beets-mpdstats = ./mpdstats.nix;
   beets-mpdstats-external = ./mpdstats-external.nix;
   beets-mpdupdate = ./mpdupdate.nix;

tests/modules/programs/beets/legacy-enable-default.nix

@@ -0,0 +1,12 @@
+{
+  home.stateVersion = "18.09";
+
+  programs.beets.settings = {
+    directory = "~/Music";
+  };
+
+  nmt.script = ''
+    assertFileExists home-files/.config/beets/config.yaml
+    assertFileContains home-files/.config/beets/config.yaml 'directory: ~/Music'
+  '';
+}