Add zsh prompt redraw regression test

tests/test_ghostty_zsh_prompt_redraw_uses_prompt_start.py

@@ -0,0 +1,174 @@
+#!/usr/bin/env python3
+"""
+Regression: zsh prompt redraws should not replay fresh-line OSC 133;A markers.
+
+Prompt themes with async redraws (such as Prezto-like setups) can call
+`zle reset-prompt` after the prompt is already visible. Ghostty's zsh shell
+integration should emit a single fresh prompt mark for the actual prompt, then
+use OSC 133;P for redraws so redraws stay in place instead of looking like
+extra prompt lines.
+"""
+
+from __future__ import annotations
+
+import os
+import pty
+import select
+import shutil
+import subprocess
+import tempfile
+import time
+from pathlib import Path
+
+
+FRESH_PROMPT = b"\x1b]133;A;cl=line\x07"
+PROMPT_START = b"\x1b]133;P;k=i\x07"
+END_COMMAND = b"\x1b]133;D\x07"
+START_OUTPUT = b"\x1b]133;C\x07"
+
+
+def _write_redrawing_zshrc(path: Path) -> None:
+    path.write_text(
+        """
+autoload -Uz add-zsh-hook
+
+setopt prompt_cr prompt_percent prompt_sp prompt_subst
+PROMPT='%F{4}%1~%f %# '
+RPROMPT=''
+
+typeset -gi _cmux_redraw_done=0
+typeset -g _cmux_redraw_fd=''
+
+_cmux_redraw_precmd() {
+  _cmux_redraw_done=0
+}
+
+_cmux_redraw_ready() {
+  emulate -L zsh
+  local fd="${1:-$_cmux_redraw_fd}"
+  if [[ -n "$fd" ]]; then
+    zle -F "$fd"
+    exec {fd}<&-
+  fi
+  _cmux_redraw_fd=''
+  (( _cmux_redraw_done )) && return 0
+  _cmux_redraw_done=1
+  zle reset-prompt
+}
+
+_cmux_redraw_line_init() {
+  if (( !_cmux_redraw_done )) && [[ -z "$_cmux_redraw_fd" ]]; then
+    exec {_cmux_redraw_fd}< <(
+      sleep 0.05
+      printf 'ready\\n'
+    )
+    zle -F "$_cmux_redraw_fd" _cmux_redraw_ready
+  fi
+}
+
+add-zsh-hook precmd _cmux_redraw_precmd
+zle -N zle-line-init _cmux_redraw_line_init
+""".lstrip(),
+        encoding="utf-8",
+    )
+
+
+def _capture_session(env: dict[str, str]) -> bytes:
+    master, slave = pty.openpty()
+    proc = subprocess.Popen(
+        ["zsh", "-d", "-i"],
+        stdin=slave,
+        stdout=slave,
+        stderr=slave,
+        env=env,
+        close_fds=True,
+    )
+    os.close(slave)
+
+    output = bytearray()
+    start = time.time()
+    phase = 0
+    try:
+        while time.time() - start < 5:
+            readable, _, _ = select.select([master], [], [], 0.2)
+            if master in readable:
+                try:
+                    chunk = os.read(master, 4096)
+                except OSError:
+                    break
+                if not chunk:
+                    break
+                output.extend(chunk)
+
+            elapsed = time.time() - start
+            if phase == 0 and elapsed > 1.0:
+                os.write(master, b"\n")
+                phase = 1
+            elif phase == 1 and elapsed > 2.5:
+                os.write(master, b"exit\n")
+                phase = 2
+    finally:
+        try:
+            proc.wait(timeout=5)
+        finally:
+            os.close(master)
+
+    return bytes(output)
+
+
+def main() -> int:
+    root = Path(__file__).resolve().parents[1]
+    wrapper_dir = root / "ghostty" / "src" / "shell-integration" / "zsh"
+    if not (wrapper_dir / ".zshenv").exists():
+        print(f"SKIP: missing Ghostty zsh wrapper at {wrapper_dir}")
+        return 0
+
+    if shutil.which("zsh") is None:
+        print("SKIP: zsh not installed")
+        return 0
+
+    base = Path(tempfile.mkdtemp(prefix="cmux_ghostty_prompt_redraw_"))
+    try:
+        home = base / "home"
+        home.mkdir(parents=True, exist_ok=True)
+        _write_redrawing_zshrc(home / ".zshrc")
+
+        env = dict(os.environ)
+        env["HOME"] = str(home)
+        env["ZDOTDIR"] = str(wrapper_dir)
+        env["GHOSTTY_ZSH_ZDOTDIR"] = str(home)
+        env["GHOSTTY_RESOURCES_DIR"] = str(root / "ghostty" / "src")
+        env.pop("GHOSTTY_SHELL_FEATURES", None)
+        env.pop("GHOSTTY_BIN_DIR", None)
+
+        output = _capture_session(env)
+
+        marker = output.find(END_COMMAND)
+        if marker == -1:
+            print("FAIL: did not observe OSC 133;D for the empty command prompt cycle")
+            return 1
+
+        end = output.find(START_OUTPUT, marker + len(END_COMMAND))
+        if end == -1:
+            end = len(output)
+
+        prompt_cycle = output[marker:end]
+        fresh_count = prompt_cycle.count(FRESH_PROMPT)
+        prompt_start_count = prompt_cycle.count(PROMPT_START)
+
+        if fresh_count != 1:
+            print(f"FAIL: expected exactly 1 fresh prompt marker after redraw, saw {fresh_count}")
+            return 1
+
+        if prompt_start_count < 1:
+            print("FAIL: expected redraw path to emit OSC 133;P prompt-start markers")
+            return 1
+
+        print("PASS: zsh prompt redraws keep a single fresh prompt marker and reuse OSC 133;P")
+        return 0
+    finally:
+        shutil.rmtree(base, ignore_errors=True)
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())