1 files changed, 30 insertions, 9 deletions
diff --git a/src/exec.zig b/src/exec.zig
index eed9297a..7d682d74 100644
--- a/src/exec.zig
+++ b/src/exec.zig
@@ -643,12 +643,22 @@ pub fn execute(p: *Pardes, id: usize, txt: []const u8) ?usize {
 /// `execute` for text a gesture took from `id`'s body when `from_body`:
 /// such text may be a bound REPL's. Run by name (`Exec ...`, whose line
 /// comes back through `execute`) or written as a command word, never.
+/// A line that starts with `#` is a comment, as in a shell: it runs as
+/// nothing, silently, wherever a line runs (exec, a ctl, the init file),
+/// so DumpConfig's report reads back as configuration whole.
+pub fn isComment(line: []const u8) bool {
+    const t = std.mem.trimStart(u8, line, " \t");
+    return t.len > 0 and t[0] == '#';
+}
+
 pub fn executeFrom(p: *Pardes, id: usize, txt: []const u8, from_body: bool) ?usize {
-    // An empty window runs its session words, and nothing else: no pane to
-    // run a command for.
+    if (isComment(commandText(txt))) return null;
+    // An empty window runs its session words, and a command line in the
+    // session's directory (execDir), as its workspace tag would.
     const pane = p.panes[id] orelse {
-        _ = executeBuiltinLine(p, id, commandText(txt));
-        return null;
+        const cmd = commandText(txt);
+        if (cmd.len == 0 or executeBuiltinLine(p, id, cmd)) return null;
+        return runCommand(p, id, cmd);
     };
     const gesture = from_body and config.commandWord(std.mem.trim(u8, txt, " \t\r\n")) == null;
     const cmd = commandText(txt);
@@ -699,7 +709,9 @@ fn runCommand(p: *Pardes, from: usize, line: []const u8) ?usize {
         p.reportFailure(from, "exec: a command line is at most 1024 bytes");
         return null;
     }
-    const src = p.panes[from] orelse return null;
+    // None asking (an empty window): the session's directory, no pane of
+    // its own to reuse.
+    const src = p.panes[from];
     const dir = p.execDir(from);
     // A directory that is not there runs nothing, as Tty makes nothing
     // there: no pane, and the write fails ENOENT.
@@ -712,7 +724,7 @@ fn runCommand(p: *Pardes, from: usize, line: []const u8) ?usize {
     // would hang that job up.
     // From a column's tag, only a finished pane in that column is reused,
     // as the new one goes in that column (placeNew).
-    const reuse: ?usize = if (p.exec_column == null and src.command != null and src.command_done and !src.command_pty) from else for (p.panes, 0..) |slot, i| {
+    const reuse: ?usize = if (p.exec_column == null and src != null and src.?.command != null and src.?.command_done and !src.?.command_pty) from else for (p.panes, 0..) |slot, i| {
         const other = slot orelse continue;
         if (p.exec_column) |c| if (if (layout.findPane(p, i)) |f| f.col != c else true) continue;
         if (other.command != null and other.command_done and !other.command_pty and std.mem.eql(u8, other.cwdSlice(), dir)) break i;
@@ -838,6 +850,7 @@ pub const acme_words = [_]struct { acme: []const u8, pardes: ?[]const u8, hint:
 pub fn executeBuiltinLine(p: *Pardes, id: usize, txt: []const u8) bool {
     const raw = commandText(txt);
     if (raw.len == 0 or p.exec_depth >= max_exec_depth) return false;
+    if (isComment(raw)) return true;
     const word_end = std.mem.indexOfAny(u8, raw, " \t") orelse raw.len;
     var renamed: [1024 + 16]u8 = undefined;
     const cmd = for (acme_words) |w| {
@@ -1032,9 +1045,12 @@ pub fn placeNew(p: *Pardes, from: usize, origin: ?usize, id: usize, kind: NewPan
             // No pane to halve, but the column holds every pane's minimum
             // with the new one's: the rows are shared out again, so what is
             // refused is only what the documented arithmetic cannot hold.
-            // +Errors goes wherever there is room, last column first; with
-            // none, its maker says the text some other way (appendErrors).
-            if (layout.shareColumn(p, f.col)) {} else if (kind == .errors) {
+            // +Errors and 9P's pane/new go wherever there is room, last
+            // column first, as acme takes rows from a window that has them
+            // before saying there are none; with none, +Errors's maker says
+            // the text some other way (appendErrors), and pane/new is
+            // refused.
+            if (layout.shareColumn(p, f.col)) {} else if (kind == .errors or kind == .fs) {
                 layout.removePane(p, id);
                 var c = p.ncol;
                 while (c > 0) {
@@ -1051,6 +1067,11 @@ pub fn placeNew(p: *Pardes, from: usize, origin: ?usize, id: usize, kind: NewPan
                 } else {
                     layout.insert(p, f.col, p.col_n[f.col], id);
                     p.unplaced.set(id);
+                    // No pane anywhere can give it rows: pane/new is refused.
+                    if (kind == .fs) {
+                        p.panes[id].?.vweight = 0;
+                        p.reportError(from, "placement", error.NoPaneRoom);
+                    }
                     return;
                 }
             } else {