broot: fix nushell integration br command

broot 1.51 renamed the printed nushell entry point from `br` to `main`,
intended to be loaded with `use` where the command takes the module's
name. Home Manager sources the snippet with `source`, so it began
defining a global `main` instead of `br`, breaking the `br` command in
nushell.

Rewrite the definition line back to `br` for the nushell shell function
so `source` keeps exposing `br` globally. Other shells are unaffected.

Fixes #9392

modules/programs/broot.nix

@@ -139,9 +139,14 @@ let
     # manipulations of the prompt.
     lib.mkAfter ''
       source ${
-        pkgs.runCommand "br.${shell}" {
-          nativeBuildInputs = [ cfg.package ];
-        } "broot --print-shell-function ${shell} > $out"
+        pkgs.runCommand "br.${shell}" { nativeBuildInputs = [ cfg.package ]; } (
+          if shell == "nushell" then
+            # broot >= 1.51 exports `main` instead of `br`.
+            # Rename back to `br` to keep `source` working.
+            "broot --print-shell-function ${shell} | sed 's/export def --env main/export def --env br/' > $out"
+          else
+            "broot --print-shell-function ${shell} > $out"
+        )
       }
     '';
 in

tests/modules/programs/broot/broot.nix

@@ -3,9 +3,20 @@
 {
   programs.broot = {
     enable = true;
+    enableBashIntegration = true;
+    enableNushellIntegration = true;
     package = (
       config.lib.test.mkStubPackage {
         name = "broot";
+        # Mimic broot >= 1.51, whose nushell shell function is named `main`.
+        buildScript = ''
+          mkdir -p $out/bin
+          cat > $out/bin/broot <<'EOF'
+          #!/bin/sh
+          echo 'export def --env main ['
+          EOF
+          chmod +x $out/bin/broot
+        '';
         extraAttrs = {
           src = config.lib.test.mkStubPackage {
             name = "broot-src";
@@ -21,8 +32,21 @@
     settings.modal = true;
   };
 
+  programs.bash.enable = true;
+  programs.nushell.enable = true;
+
   nmt.script = ''
     assertFileExists home-files/.config/broot/conf.hjson
     assertFileContains home-files/.config/broot/conf.hjson '"modal": true'
+    assertFileRegex home-files/.bashrc 'source /nix/store/.*-br\.bash'
+    assertFileRegex home-files/.config/nushell/config.nu \
+      'source /nix/store/.*-br\.nushell'
+
+    brNushell=$(
+      sed -n 's/^[[:space:]]*source \(\/nix\/store\/.*-br\.nushell\)$/\1/p' \
+        "$(_abs home-files/.config/nushell/config.nu)"
+    )
+    assertFileRegex "$brNushell" 'export def --env br \['
+    assertFileNotRegex "$brNushell" 'export def --env main \['
   '';
 }