Mount dials: a relative socket path is a bad dial address, a socket path not there says no such socket (ENOENT), and the hint says tcp! takes a numeric address

`Mount peer rel/x.sock` dialled relative to wherever the editor ran;
`Mount peer unix!/nonexistent` said `dial failed: no answer` (EIO); and
the hint offered `tcp!host!port` where only a numeric address is taken.

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

1 files changed, 12 insertions, 1 deletions

diff --git a/src/builtins.zig b/src/builtins.zig
index ca80be26..907650bd 100644
--- a/src/builtins.zig
+++ b/src/builtins.zig
@@ -804,9 +804,20 @@ pub const Mount = struct {
         if (dial.len == 0) return c.p.reportFailure(c.id, e_args);
         c.p.fs.mount(c.p.gpa, name, dial) catch |err| {
             var said: [200]u8 = undefined;
-            if (err == error.BadDial) return c.p.reportFailure(c.id, std.fmt.bufPrint(&said, "Mount: bad dial address: {s} (unix!/path, tcp!host!port, or a session name)", .{dial[0..@min(dial.len, 100)]}) catch "Mount: bad dial address");
+            if (err == error.BadDial) return c.p.reportFailure(c.id, std.fmt.bufPrint(&said, "Mount: bad dial address: {s} (unix!/path, /path, tcp!<numeric-ip>!<port>, or a session name)", .{dial[0..@min(dial.len, 100)]}) catch "Mount: bad dial address");
             return c.p.reportError(c.id, "Mount", err);
         };
+        // A socket path that is not there: said so (ENOENT), not a dial
+        // that went unanswered.
+        const sock_path: ?[]const u8 = if (std.mem.startsWith(u8, dial, "unix!")) dial[5..] else if (dial.len > 0 and dial[0] == '/') dial else null;
+        if (sock_path) |path| if (@import("exec.zig").kindOf(path) == null) {
+            if (c.p.fs.mounts.pop()) |gone| {
+                c.p.gpa.free(gone.name);
+                c.p.gpa.free(gone.dial);
+            }
+            var said: [200]u8 = undefined;
+            return c.p.reportFailure(c.id, std.fmt.bufPrint(&said, "Mount {s}: {s}: no such socket", .{ name, path[0..@min(path.len, 100)] }) catch "Mount: no such socket");
+        };
         // A mount that cannot be reached is said now, and taken back, not
         // found out by the first look through it.
         const reached = reached: {