A Save into a directory that is not there says no such directory, ENOENT

It failed EIO with `file not found`, which named no file that was
missing. It says `Save <path>: no such directory`, and a late failure
saying `no such` answers ENOENT, as a builtin's does.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

3 files changed, 16 insertions, 4 deletions

diff --git a/src/9p_io.zig b/src/9p_io.zig
index 2130db27..4c9c9bcf 100644
--- a/src/9p_io.zig
+++ b/src/9p_io.zig
@@ -315,7 +315,11 @@ pub const Listener = struct {
         // ponytail: one slot, so a failure of another client's effects that
         // settle in the same wait is told to this write too.
         if (l.core == core and core.fs.late_failure_len != 0) {
-            const failed = pardes.ctlfs.failText(req.tag, pardes.ctlfs.E.IO, core.fs.late_failure[0..core.fs.late_failure_len]);
+            const late = core.fs.late_failure[0..core.fs.late_failure_len];
+            // What is not there (`no such directory`) is ENOENT, as a
+            // builtin's failure saying so is (ctl.failureErrno).
+            const errno = if (std.mem.indexOf(u8, late, "no such") != null) pardes.ctlfs.E.NOENT else pardes.ctlfs.E.IO;
+            const failed = pardes.ctlfs.failText(req.tag, errno, late);
             // Its err record says it (the path in it); the msg the failure
             // was also said as goes, as a builtin's failing a write does.
             pardes.ctlfs.events.dropMessage(core, core.fs.late_failure[0..core.fs.late_failure_len]);
diff --git a/src/pardes.zig b/src/pardes.zig
index 1afb1e24..27cbf383 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -5271,8 +5271,16 @@ pub const Pardes = struct {
             // The `-%` spelling fs.zig already uses for "make this dirty".
             f.saved_revision = f.revision -% 1;
         };
-        var what: [limits.host_path_cap + 8]u8 = undefined;
-        p.reportError(id, std.fmt.bufPrint(&what, "Save {s}", .{path}) catch "Save", err);
+        var what: [limits.host_path_cap + 32]u8 = undefined;
+        // A write into a directory that is not there: said so, in the words
+        // a mount reads as ENOENT.
+        const parent = std.fs.path.dirname(path) orelse "/";
+        const no_dir = err == error.FileNotFound or err == error.NotDir or
+            (if (comptime hosted) (if (filesystem.localPath(parent)) |local| !exec.isDirectory(local) else false) else false);
+        if (no_dir)
+            p.reportFailure(id, std.fmt.bufPrint(&what, "Save {s}: no such directory", .{path}) catch "Save: no such directory")
+        else
+            p.reportError(id, std.fmt.bufPrint(&what, "Save {s}", .{path}) catch "Save", err);
         const said = if (p.panes[id]) |pane| pane.msg[0..pane.msg_len] else "Save failed";
         const kept = @import("Messages.zig").clip(said, p.fs.late_failure.len);
         @memcpy(p.fs.late_failure[0..kept.len], kept);
diff --git a/test/fs.py b/test/fs.py
index d2cd631c..f759d185 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -387,7 +387,7 @@ def discovery(binary, embedded=False):
                 client.write(f'/pane/{unsaved}/ctl', b'Save /nonexistent-pardes-dir/x.txt\n')
                 raise AssertionError('a Save into a missing directory succeeded')
             except OSError as refused:
-                assert 'Save /nonexistent-pardes-dir/x.txt: ' in str(refused), refused
+                assert 'Save /nonexistent-pardes-dir/x.txt: no such directory' in str(refused), refused
             assert f'err {unsaved} ctl: Save /nonexistent-pardes-dir/x.txt: '.encode() in client.read('/log'), client.read('/log')
             client.remove(f'/pane/{unsaved}')