From 03d53e064e4e923ca67a34cd1725cc92d61efc48 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=81ukasz=20Niemier?= <~@hauleth.dev>
Date: Wed, 21 Jan 2026 11:28:03 +0100
Subject: [PATCH] Conform to 9p specs when walking through directories

First step must always succeed, otherwise return error. Subsequent steps
can end without failure.
---
 src/e9p_fs.erl | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/e9p_fs.erl b/src/e9p_fs.erl
index 1dfcc73..a3a11a9 100644
--- a/src/e9p_fs.erl
+++ b/src/e9p_fs.erl
@@ -8,7 +8,7 @@
 
 -export([
          init/1,
-         root/2,
+         root/3,
          walk/3,
          open/3,
          create/5,
@@ -121,6 +121,11 @@ do_walk(_Mod, QID, [], State, Acc) ->
     {ok, {QID, lists:reverse(Acc)}, State};
 do_walk(Mod, QID0, [P | Rest], State0, Acc) ->
     case Mod:walk(QID0, P, State0) of
+        {false, State} when Acc =:= [] ->
+            % Per specification walk to first entry in name list must succeed
+            % (if any) otherwise return error. In subsequent steps we return
+            % successful list and last succeeded QID
+            {error, io_lib:format("Failed walk to ~p", [P]), State};
         {false, State} ->
             {ok, {QID0, lists:reverse(Acc)}, State};
         {QID, State} ->
-- 
2.51.2