hardening and bugfixing prior to stable release

scripts/ptysize.py

@@ -0,0 +1,50 @@
+"""Spawn a child on a pty whose window size is what you asked for.
+
+`pty.fork()` leaves the new terminal at **0 rows by 0 columns**, and nothing
+fixes that afterwards: `COLUMNS`/`LINES` in the environment are a shell
+convention that `ioctl(TIOCGWINSZ)` has never heard of, so `process.stdout.rows`
+in the child stays 0 however they are set.
+
+That is not a detail. A driver that forgets the ioctl is testing a terminal no
+user has, and it lied to us once already — the enquirer `Form` under it returned
+`{}` for reasons that had nothing to do with the code under test. See the
+`terminalSize` comment in `packages/nopy/src/nopy.prompts.ts`.
+
+So the size is always set explicitly here, including when it is set to 0: the
+degenerate terminal is worth testing, but only on purpose.
+"""
+
+import fcntl
+import os
+import pty
+import struct
+import termios
+
+
+def set_winsize(fd, rows, cols):
+    fcntl.ioctl(fd, termios.TIOCSWINSZ, struct.pack("HHHH", rows, cols, 0, 0))
+
+
+def spawn(cmd, rows, cols, env=None):
+    """Fork `cmd` onto a pty sized `rows` x `cols`. Returns (pid, fd)."""
+    pid, fd = pty.fork()
+    if pid == 0:
+        os.environ["TERM"] = "xterm-256color"
+        # Kept in step with the ioctl so that a program reading either one gets
+        # the same answer. The ioctl is what actually matters.
+        os.environ["COLUMNS"] = str(cols)
+        os.environ["LINES"] = str(rows)
+        for key, value in (env or {}).items():
+            os.environ[key] = value
+        os.execvp(cmd[0], cmd)
+
+    set_winsize(fd, rows, cols)
+    return pid, fd
+
+
+def size_from_env(default_rows=50, default_cols=200):
+    """`PTY_ROWS` / `PTY_COLS`, so a caller can ask for the 0x0 case."""
+    return (
+        int(os.environ.get("PTY_ROWS", default_rows)),
+        int(os.environ.get("PTY_COLS", default_cols)),
+    )