From 30d40f20dd19a44b7c54193db59980d94d5517dd Mon Sep 17 00:00:00 2001
From: shum <github.shum@liber.li>
Date: Fri, 25 Sep 2026 12:51:14 +0000
Subject: [PATCH] python: match backend switch error text

---
 .../src/simplex_chat/_native.py                |  4 ++--
 .../tests/test_native_cache.py                 | 18 +++++++++++++++---
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/packages/simplex-chat-python/src/simplex_chat/_native.py b/packages/simplex-chat-python/src/simplex_chat/_native.py
index 009ff9a1e0..6918026cd3 100644
--- a/packages/simplex-chat-python/src/simplex_chat/_native.py
+++ b/packages/simplex-chat-python/src/simplex_chat/_native.py
@@ -230,8 +230,8 @@ def lib_for(backend: Backend) -> ctypes.CDLL:
         if _lib is not None:
             if _backend != backend:
                 raise RuntimeError(
-                    f"libsimplex already loaded with backend={_backend!r}; "
-                    f"cannot switch to {backend!r} in the same process"
+                    f"libsimplex already loaded with backend={_backend}; "
+                    f"cannot switch to {backend} in the same process"
                 )
             return _lib
         libs_dir = _resolve_libs_dir(backend)
diff --git a/packages/simplex-chat-python/tests/test_native_cache.py b/packages/simplex-chat-python/tests/test_native_cache.py
index 6c4f2a923d..5bd68ddfcd 100644
--- a/packages/simplex-chat-python/tests/test_native_cache.py
+++ b/packages/simplex-chat-python/tests/test_native_cache.py
@@ -3,7 +3,8 @@ from pathlib import Path
 
 import pytest
 
-from simplex_chat._native import _cache_root, _download, _resolve_libs_dir
+from simplex_chat import _native
+from simplex_chat._native import _cache_root, _download, _resolve_libs_dir, lib_for
 from simplex_chat._version import LIBS_VERSION
 
 
@@ -97,7 +98,18 @@ def test_libc_on_windows_is_ucrt(monkeypatch):
     loaded: list[str | None] = []
     monkeypatch.setattr("sys.platform", "win32")
     monkeypatch.setattr("ctypes.CDLL", lambda name: loaded.append(name))
-    from simplex_chat import _native
-
     _native._load_libc()
     assert loaded == ["ucrtbase"]
+
+
+def test_lib_for_rejects_backend_switch(monkeypatch):
+    monkeypatch.setattr(_native, "_lib", object())
+    monkeypatch.setattr(_native, "_backend", "sqlite")
+    monkeypatch.setattr(
+        _native, "_resolve_libs_dir", lambda _: pytest.fail("must not resolve libs")
+    )
+    with pytest.raises(RuntimeError) as exc:
+        lib_for("postgres")
+    assert str(exc.value) == (
+        "libsimplex already loaded with backend=sqlite; cannot switch to postgres in the same process"
+    )