fix nix bash wrapper detection, add more completion keywords

bin/main.ml

@@ -281,6 +281,34 @@ let nix_wrapper_target path =
     end
   with _ -> None
 
+(* detect nix bash/sh wrapper scripts that exec a real binary.
+ * nix sometimes generates small shell scripts (e.g. to set env vars like
+ * XDG_CONFIG_HOME) that exec the real binary. these look like:
+ *   #!/nix/store/.../bash -e
+ *   export FOO=...
+ *   exec -a "$0" "/nix/store/.../bin/.foo-wrapped" "$@"
+ * we extract the exec target path and resolve through it. *)
+let nix_script_wrapper_target path =
+  try
+    let real = Unix.realpath path in
+    let ic = open_in real in
+    let size = in_channel_length ic in
+    if size > 4096 then (close_in ic; None)
+    else begin
+      let contents = Bytes.create size in
+      really_input ic contents 0 size; close_in ic;
+      let contents = Bytes.to_string contents in
+      if not (contains_str contents "exec") then None
+      else
+        let re = Str.regexp "exec[ \t]+\\(-a[ \t]+\"\\$0\"[ \t]+\\)?\"?\\(/nix/store/[a-z0-9]+-[^\" \t\n]+/bin/[a-zA-Z0-9._-]+\\)\"?" in
+        try ignore (Str.search_forward re contents 0);
+          let target = Str.matched_group 2 contents in
+          let target = Unix.realpath target in
+          if Sys.file_exists target then Some target else None
+        with Not_found -> None
+    end
+  with _ -> None
+
 (* heuristic filter for binary names that should never be indexed.
  * skips: empty names, "-", dotfiles, libraries (lib-prefix), daemon wrappers
  * (suffixes -daemon, -wrapped), shared objects (.so suffix), and names with no
@@ -299,25 +327,37 @@ let skip_name name =
  *   Try_native_and_help — try native nushell completion first, fall back to --help *)
 type bin_class = Skip | Try_help | Try_native_and_help
 
+(* classify an elf binary path for indexing. *)
+let classify_elf path =
+  let scan = elf_scan path ["-h"; "completion"] in
+  if Hashtbl.mem scan "completion" then Try_native_and_help
+  else if Hashtbl.mem scan "-h" then Try_help
+  else Skip
+
 (* classify a binary to decide the indexing strategy.
  * decision tree:
  *   1. nushell builtin or bad name -> Skip
  *   2. not executable -> Skip
- *   3. script (has shebang) -> Try_help (scripts can't have native completions)
+ *   3. script (has shebang) -> resolve through nix script wrapper if possible,
+ *      otherwise Try_help
  *   4. elf binary containing "completion" -> Try_native_and_help
  *   5. elf binary containing "-h" -> Try_help
- *   6. nix wrapper -> Try_help (the wrapper itself is just an exec shim)
+ *   6. nix c wrapper -> Try_help (the wrapper itself is just an exec shim)
  *   7. otherwise -> Skip (binary has no help infrastructure) *)
 let classify_binary bindir name =
   if is_nushell_builtin name || skip_name name then Skip
   else
     let path = Filename.concat bindir name in
     if not (is_executable path) then Skip
-    else if is_script path then Try_help
+    else if is_script path then
+      match nix_script_wrapper_target path with
+      | Some target ->
+        let cls = classify_elf target in
+        if cls <> Skip then cls else Try_help
+      | None -> Try_help
     else
-      let scan = elf_scan path ["-h"; "completion"] in
-      if Hashtbl.mem scan "completion" then Try_native_and_help
-      else if Hashtbl.mem scan "-h" then Try_help
+      let cls = classify_elf path in
+      if cls <> Skip then cls
       else if nix_wrapper_target path <> None then Try_help
       else Skip
 
@@ -352,6 +392,7 @@ let try_native_completion bin_path =
     [bin_path; "--completion"; "nushell"];
     [bin_path; "generate-completion"; "nushell"];
     [bin_path; "--generate-completion"; "nushell"];
+    [bin_path; "gen-completions"; "nushell"];
     [bin_path; "shell-completions"; "nushell"];
   ]