A name shows its own backslash as \\, and a terminal tag never carries a raw newline

With `\n` for a newline and `\xNN` for a bad byte, a name holding a
backslash and an n read back as one holding a newline. Names in /index,
the log and a terminal's tag now double their own backslashes; and a
terminal's directory with a newline no longer breaks its tag.

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

1 files changed, 15 insertions, 4 deletions

diff --git a/src/ninep/events.zig b/src/ninep/events.zig
index 3da6f723..8b8f8637 100644
--- a/src/ninep/events.zig
+++ b/src/ninep/events.zig
@@ -358,10 +358,10 @@ fn sanitize(record: []const u8, out: []u8) []u8 {
 }
 
 /// `text` as one line of UTF-8 a reader can split and decode, as /log and
-/// /index show names: a newline is `\n` (a name with one stays readable as
-/// what it is, not run into the next), any other control character, DEL
-/// or C1 control (U+0080-U+009F) a space, and a byte that is not UTF-8
-/// `\xNN`. `out` of 4 bytes a byte of `text` holds it all.
+/// /index show names: a backslash is `\\`, a newline `\n` (a name with one
+/// stays readable as what it is, not run into the next), any other control
+/// character, DEL or C1 control (U+0080-U+009F) a space, and a byte that
+/// is not UTF-8 `\xNN`. `out` of 4 bytes a byte of `text` holds it all.
 pub fn shown(text: []const u8, out: []u8) []u8 {
     return shownAs(text, out, true);
 }
@@ -372,6 +372,14 @@ fn shownAs(text: []const u8, out: []u8, escape_newline: bool) []u8 {
     const body = text;
     while (i < body.len and w + 4 <= out.len) {
         const c = body[i];
+        // A name's own backslash is `\\`, so `\n` and `\xNN` read back as
+        // the escapes they are, never as a name that held them.
+        if (c == '\\' and escape_newline) {
+            @memcpy(out[w..][0..2], "\\\\");
+            w += 2;
+            i += 1;
+            continue;
+        }
         if (c == '\n' and escape_newline) {
             @memcpy(out[w..][0..2], "\\n");
             w += 2;
@@ -1312,6 +1320,9 @@ test "a record is one line of UTF-8: DEL and C1 are spaces, bytes not UTF-8 are
     var out: [64]u8 = undefined;
     var name: [64]u8 = undefined;
     try testing.expectEqualStrings("/tmp/two\\nlines", shown("/tmp/two\nlines", &name));
+    // A backslash of the name's own is doubled: `\n` in a name differs from
+    // a newline in one.
+    try testing.expectEqualStrings("/tmp/a\\\\nb", shown("/tmp/a\\nb", &name));
     try testing.expectEqualStrings("msg - a b c \\xff d\n", sanitize("msg - a\x7fb\xc2\x85c \xff d\n", &out));
     try testing.expectEqualStrings("msg - caf\xc3\xa9\n", sanitize("msg - caf\xc3\xa9\n", &out));
 }