Shell refuses a name that is no executable, and bare restores the default

Shell took any word and the host quietly ran another shell at the next
spawn. It now refuses a path or name that is not executable ("Shell: x:
no executable by that name", failing a ctl write, logged err), a bare
Shell goes back to the default, and a default $SHELL that is not
executable falls back to /bin/sh. shellset's golden takes the refusal on
the message row (re-recorded by name).

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

1 files changed, 18 insertions, 0 deletions

diff --git a/src/exec.zig b/src/exec.zig
index 6de7991c..0a7e71f9 100644
--- a/src/exec.zig
+++ b/src/exec.zig
@@ -761,6 +761,24 @@ pub fn applySettingBuiltin(p: *Pardes, setting: config.Runtime.Setting, arg: ?[]
             if (!p.settings.requestFont(matches[0].path, matches[0].name, spec.size_hundredths)) return;
             p.font_request_taken = false;
         },
+        // A shell that is no executable is refused, not taken and quietly
+        // replaced at the next spawn; bare, it goes back to the default.
+        .shell => {
+            const want = std.mem.trim(u8, arg orelse "", " \t\r\n");
+            if (want.len == 0) {
+                p.settings.shell.requested.clear();
+                p.settings.shell.pending = true;
+                return;
+            }
+            if (comptime pardes.hosted) {
+                var buf: [std.fs.max_path_bytes]u8 = undefined;
+                if (@import("host_io.zig").Shell.find(want, &buf) == null) {
+                    var text: [320]u8 = undefined;
+                    return p.reportFailure(p.active, std.fmt.bufPrint(&text, "Shell: {s}: no executable by that name", .{want[0..@min(want.len, 255)]}) catch "Shell: no such executable");
+                }
+            }
+            if (!p.settings.apply(setting, want) and p.announce) p.reportFailure(p.active, "Shell: does not take that value");
+        },
         else => if (!p.settings.apply(setting, arg) and p.announce) {
             var text: [96]u8 = undefined;
             const takes = if (setting.action == .toggle) "takes on or off" else "does not take that value";