Forwarding to a running pardes says why in words: a name with a newline is "a file name is one line", never NotOneLine

The forwarding refusal printed the error's name for anything the
session itself did not answer: NotOneLine, NotAFileName,
NoWorkingDirectory. Those are now sentences, a dial failure is said as
the message row says one, and any other error is its name's words.

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

1 files changed, 26 insertions, 1 deletions

diff --git a/src/main.zig b/src/main.zig
index 101a5be3..6c5eaba1 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -98,6 +98,30 @@ const help_text =
     \\
 ;
 
+/// A forwarding failure in words, never an error's name: the ones this
+/// file raises said outright, any other as its name's words (`NotFound`,
+/// `not found`), a dial's as Messages says it.
+fn forwardWords(err: anyerror, buf: []u8) []const u8 {
+    return switch (err) {
+        error.NotOneLine => "a file name is one line, and this one holds a newline",
+        error.NotAFileName => "names a directory, not a file",
+        error.NoWorkingDirectory => "this shell's working directory is gone",
+        else => if (pardes.Messages.dialReason(err)) |why| why else words: {
+            var n: usize = 0;
+            for (@errorName(err), 0..) |c, i| {
+                if (n + 2 > buf.len) break;
+                if (std.ascii.isUpper(c) and i > 0) {
+                    buf[n] = ' ';
+                    n += 1;
+                }
+                buf[n] = std.ascii.toLower(c);
+                n += 1;
+            }
+            break :words buf[0..n];
+        },
+    };
+}
+
 /// `--wait` after a forwarded look, as plan9port's E reads acme's log: the
 /// pane `path` landed in (the one it already had, if open), then /log
 /// followed on one connection until that pane's `del` -- exit 0 -- or the
@@ -401,7 +425,8 @@ fn nativeMain(init: std.process.Init) !void {
         ninep_io.Client.probe(arena, parent.dial) catch break :forwarding;
         const Refuse = struct {
             fn with(io: std.Io, what: []const u8, err: anyerror) noreturn {
-                const why = if (err == error.Remote) ninep_io.Client.lastSaid() else @errorName(err);
+                var words_buf: [128]u8 = undefined;
+                const why = if (err == error.Remote) ninep_io.Client.lastSaid() else forwardWords(err, &words_buf);
                 var buf: [8192]u8 = undefined;
                 const text = std.fmt.bufPrint(&buf, "pardes: {s}: {s}\n", .{ what[0..@min(what.len, 4096)], why }) catch "pardes: refused\n";
                 std.Io.File.stderr().writeStreamingAll(io, text) catch {};