bash: support bash completion

tests/modules/programs/bash/completion.nix

@@ -0,0 +1,23 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  programs.bash.enable = true;
+
+  test.stubs.bash-completion = { };
+
+  nmt.script = ''
+    assertFileExists home-files/.bashrc
+
+    assertFileContains \
+      home-files/.bashrc \
+      'if [[ ! -v BASH_COMPLETION_VERSINFO ]]; then'
+    assertFileContains \
+      home-files/.bashrc \
+      '  . "@bash-completion@/etc/profile.d/bash_completion.sh"'
+    assertFileContains \
+      home-files/.bashrc \
+      'fi'
+  '';
+}

tests/modules/programs/bash/default.nix

@@ -1,4 +1,5 @@
 {
+  bash-completion = ./completion.nix;
   bash-logout = ./logout.nix;
   bash-session-variables = ./session-variables.nix;
 }

tests/modules/programs/bash/logout.nix

@@ -6,6 +6,7 @@ with lib;
   config = {
     programs.bash = {
       enable = true;
+      enableCompletion = false;
 
       logoutExtra = ''
         clear-console

tests/modules/programs/bash/session-variables.nix

@@ -6,6 +6,7 @@ with lib;
   config = {
     programs.bash = {
       enable = true;
+      enableCompletion = false;
 
       sessionVariables = {
         V1 = "v1";