Fix shell routes on Windows without PTY support

tests/test_shell_routes.py

@@ -1,9 +1,66 @@
-"""Tests for shell_routes.py — _find_line_break helper.
-Imports the function directly since it has no app dependencies."""
+"""Tests for shell_routes.py helpers."""
+
+import builtins
+import importlib.util
+import json
+import sys
+from pathlib import Path
+from types import SimpleNamespace
 
 from routes.shell_routes import _find_line_break
 
 
+def test_shell_routes_import_without_posix_pty_modules(monkeypatch):
+    """Native Windows has no fcntl/termios; importing routes must still work."""
+    real_import = builtins.__import__
+
+    def fake_import(name, globals=None, locals=None, fromlist=(), level=0):
+        if name in {"fcntl", "pty"}:
+            raise ImportError(f"No module named {name!r}")
+        return real_import(name, globals, locals, fromlist, level)
+
+    monkeypatch.setattr(builtins, "__import__", fake_import)
+    cached_modules = {name: sys.modules.pop(name, None) for name in ("fcntl", "pty")}
+
+    module_path = Path(__file__).resolve().parents[1] / "routes" / "shell_routes.py"
+    spec = importlib.util.spec_from_file_location("_shell_routes_without_pty", module_path)
+    module = importlib.util.module_from_spec(spec)
+    sys.modules[spec.name] = module
+    try:
+        spec.loader.exec_module(module)
+    finally:
+        sys.modules.pop(spec.name, None)
+        for name, cached_module in cached_modules.items():
+            if cached_module is not None:
+                sys.modules[name] = cached_module
+
+    assert module.PTY_SUPPORTED is False
+    assert module._find_line_break(b"ok\n") == (2, 1)
+
+
+async def test_generate_pty_reports_explicit_unsupported_error(monkeypatch):
+    """Clients can distinguish unsupported PTY mode from process failures."""
+    import routes.shell_routes as shell_routes
+
+    monkeypatch.setattr(shell_routes, "PTY_SUPPORTED", False)
+    monkeypatch.setattr(shell_routes, "_PTY_IMPORT_ERROR", ImportError("No module named 'termios'"))
+
+    request = SimpleNamespace(is_disconnected=lambda: False)
+    events = [
+        json.loads(chunk.removeprefix("data: ").strip())
+        async for chunk in shell_routes._generate_pty("echo hi", 5, request)
+    ]
+
+    assert events == [
+        {
+            "stream": "stderr",
+            "data": "PTY streaming is not supported on this platform: No module named 'termios'",
+            "error": shell_routes.PTY_UNSUPPORTED_ERROR,
+        },
+        {"exit_code": -1, "error": shell_routes.PTY_UNSUPPORTED_ERROR},
+    ]
+
+
 class TestFindLineBreak:
     """Test line-break detection in byte buffers."""