texlive: always require at least one extra package

Fixes #526

modules/programs/texlive.nix

@@ -6,6 +6,8 @@ let
 
   cfg = config.programs.texlive;
 
+  texlivePkgs = cfg.extraPackages pkgs.texlive;
+
 in
 
 {
@@ -16,7 +18,8 @@ in
       enable = mkEnableOption "Texlive";
 
       extraPackages = mkOption {
-        default = self: {};
+        default = tpkgs: { inherit (tpkgs) collection-basic; };
+        defaultText = "tpkgs: { inherit (tpkgs) collection-basic; }";
         example = literalExample ''
           tpkgs: { inherit (tpkgs) collection-fontsrecommended algorithms; }
         '';
@@ -32,8 +35,16 @@ in
   };
 
   config = mkIf cfg.enable {
+    assertions = [
+      {
+        assertion = texlivePkgs != {};
+        message = "Must provide at least one extra package in"
+          + " 'programs.texlive.extraPackages'.";
+      }
+    ];
+
     home.packages = [ cfg.package ];
-    programs.texlive.package =
+
-      pkgs.texlive.combine (cfg.extraPackages pkgs.texlive);
+    programs.texlive.package = pkgs.texlive.combine texlivePkgs;
   };
 }

tests/default.nix

@@ -18,6 +18,7 @@ import nmt {
   tests = {
     "git/with-most-options" = ./modules/programs/git.nix;
     "git/with-str-extra-config" = ./modules/programs/git-with-str-extra-config.nix;
+    texlive-minimal = ./modules/programs/texlive-minimal.nix;
     xresources = ./modules/xresources.nix;
   };
 }

tests/modules/programs/texlive-minimal.nix

@@ -0,0 +1,13 @@
+{ config, lib, ... }:
+
+with lib;
+
+{
+  config = {
+    programs.texlive.enable = true;
+
+    nmt.script = ''
+      assertFileExists home-path/bin/tex
+    '';
+  };
+}