A name write to a terminal, image or PDF and Edit on a pane with no text are refused EINVAL, in words a mount maps so: `invalid rename: ...` and the data write's own refusal

`rename not allowed: ...` went out EPERM, and `Edit ,d` on a PDF ran
and failed late, EIO, while a data write there was EINVAL. The rename
refusal now says `invalid rename` with EINVAL, and Edit on a pane with
no text is refused before anything runs with the data write's words.

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

2 files changed, 22 insertions, 5 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index fa6310bb..1bf916a9 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -991,6 +991,10 @@ pub fn writePane(p: *Pardes, req: Req, pane: *Pane) Reply {
                 if (apply) _ = p.answerQuestion(id, if (choice[0] == '-') null else choice[0]);
             } else if (!apply) {
                 if (checkBuiltin(p, req, line, .pane)) |refusal| return refusal;
+                // Edit on a pane with no text is the refusal a data write
+                // there gets, EINVAL, before anything runs.
+                if (std.mem.startsWith(u8, line, "Edit") and pane_files.fileOf(p.panes[p.paneBySerial(serial).?].?) == null)
+                    return tree.failText(req.tag, E.INVAL, pane_files.e_no_text);
             } else if (runBuiltin(p, req, p.paneBySerial(serial).?, line)) |refusal| {
                 return refusal;
             }
@@ -4133,3 +4137,15 @@ test "a Rename that reaches other files previews them, says so, and is the pane
     try testing.expectEqual(preview.serial, p.fs.lsp_result.?);
     try testing.expect(th.logHas(p, "Rename: 2 edit(s) across files, previewed, not applied"));
 }
+
+test "Edit on an image pane is refused as a data write there is, EINVAL, before it runs" {
+    const p = try withFile(testing.allocator, "x\n");
+    defer p.deinit();
+    const doc = try p.newDocPane(p.freeSlot().?);
+    doc.image = .{ .path = try p.gpa.dupe(u8, "/tmp/pardes-pic.ppm") };
+    const edit = wr(p, Node.of(doc.serial, .ctl), "Edit ,d\n");
+    const data = wr(p, Node.of(doc.serial, .data), "x");
+    try testing.expectEqual(E.INVAL, edit.errno());
+    try testing.expectEqualStrings(data.reply.ename, edit.reply.ename);
+    try testing.expectEqual(E.INVAL, wr(p, Node.of(doc.serial, .name), "/tmp/other.ppm\n").errno());
+}
diff --git a/src/ninep/pane.zig b/src/ninep/pane.zig
index f69813b0..48c2888e 100644
--- a/src/ninep/pane.zig
+++ b/src/ninep/pane.zig
@@ -936,10 +936,11 @@ fn writeName(p: *Pardes, req: Req, id: usize, pane: *Pane) Reply {
     const name = if (std.mem.endsWith(u8, req.data, "\n")) req.data[0 .. req.data.len - 1] else req.data;
     if (name.len == 0) return tree.failText(req.tag, E.INVAL, e_name_char ++ ": an empty name");
     if (nameFault(name)) |why| return tree.failText(req.tag, E.INVAL, why);
-    if (fileOf(pane) == null) return tree.failText(req.tag, E.PERM, if (pane.isTerminal())
-        "rename not allowed: a terminal is named by its shell's directory; cd there, or Tty in another"
+    // Words 9ns maps to EINVAL, as every refusal of a name here.
+    if (fileOf(pane) == null) return tree.failText(req.tag, E.INVAL, if (pane.isTerminal())
+        "invalid rename: a terminal is named by its shell's directory; cd there, or Tty in another"
     else
-        "rename not allowed: an image or PDF is named by the file it shows");
+        "invalid rename: an image or PDF is named by the file it shows");
     var home_buf: [4096]u8 = undefined;
     const full = std.fs.path.resolvePosix(p.scratch.allocator(), &.{ pardes.Pardes.paneDir(pane), fs.expandHome(name, &home_buf) }) catch
         return Reply.fail(req.tag, E.NOMEM);
@@ -1126,8 +1127,8 @@ test "a terminal is listed as term with its directory as name" {
     ) != null);
     try testing.expectEqualStrings("/work/dir\n", rd(p, Node.of(pane.serial, .name), 0, 4096).bytes);
     const refused = wr(p, Node.of(pane.serial, .name), "/elsewhere\n");
-    try testing.expectEqual(E.PERM, refused.errno());
-    try testing.expect(std.mem.startsWith(u8, refused.reply.ename, "rename not allowed: a terminal is named"));
+    try testing.expectEqual(E.INVAL, refused.errno());
+    try testing.expect(std.mem.startsWith(u8, refused.reply.ename, "invalid rename: a terminal is named"));
 }
 
 test "body reads at any offset and writes append" {