erlang: wire file:list_dir/1 against file-list-dir (Phase 8, +4 ffi tests); 729/729, progress log

lib/erlang/tests/ffi.sx

@@ -141,9 +141,24 @@
   "true")
 
 (er-ffi-test
-  "file:list_dir unregistered"
-  (er-lookup-bif "file" "list_dir" 1)
-  nil)
+  "file:list_dir ok tag"
+  (ffi-nm (ffi-ev "element(1, file:list_dir(\"lib/erlang\"))"))
+  "ok")
+
+(er-ffi-test
+  "file:list_dir non-empty"
+  (ffi-nm (ffi-ev "case file:list_dir(\"lib/erlang\") of {ok, L} -> length(L) > 3 end"))
+  "true")
+
+(er-ffi-test
+  "file:list_dir entries are binaries"
+  (ffi-nm (ffi-ev "case file:list_dir(\"lib/erlang\") of {ok, L} -> is_binary(hd(L)) end"))
+  "true")
+
+(er-ffi-test
+  "file:list_dir missing enoent"
+  (ffi-nm (ffi-ev "element(2, file:list_dir(\"/no/such/dir/xyz\"))"))
+  "enoent")
 
 ;; ── Still deferred (no host primitive): httpc (HTTP client, v2),
 ;; sqlite-* (v2 indexes). Assert NOT registered so a future iteration