add tests

tests/external_zip_test.py

@@ -0,0 +1,64 @@
+"""Regression test: load the plugin the way Electrum loads an *external* zip.
+
+When a user installs the plugin via Electrum's "Plugins" dialog from a .zip,
+Electrum 4.7.x imports it under the synthetic top-level package
+``electrum_external_plugins.bal`` and only executes the package ``__init__``
+and the ``qt`` module.  It does NOT pre-register the synthetic root package
+nor the nested ``gui`` / ``gui.qt`` sub-packages.
+
+A naive ``from .gui.qt.plugin import Plugin`` in ``qt.py`` therefore fails with::
+
+    ModuleNotFoundError: No module named 'electrum_external_plugins'
+
+This test reproduces that exact loading sequence against the built zip and
+asserts that the resilient ``qt.py`` shim resolves the ``Plugin`` class.
+
+Usage:
+    QT_QPA_PLATFORM=offscreen \
+    PYTHONPATH=<electrum-src> \
+    python3 tests/external_zip_test.py <path-to-bal-electrum-plugin.zip>
+"""
+
+import importlib.util
+import sys
+import zipimport
+
+
+def main(zip_path: str) -> int:
+    base = "electrum_external_plugins.bal"
+    gui = "qt"
+    dirname = "bal"  # directory name inside the zip archive
+
+    def exec_module_from_spec(spec, path):
+        # Mirrors electrum.plugin.PluginManager.exec_module_from_spec
+        module = importlib.util.module_from_spec(spec)
+        sys.modules[path] = module
+        spec.loader.exec_module(module)
+        return module
+
+    zi = zipimport.zipimporter(zip_path)
+
+    # Step 1: load the package __init__ as electrum_external_plugins.bal
+    init_spec = zi.find_spec(dirname)
+    assert init_spec is not None, "could not find package __init__ inside zip"
+    exec_module_from_spec(init_spec, base)
+
+    # Step 2: load the qt entry-point as electrum_external_plugins.bal.qt
+    full = f"{base}.{gui}"
+    spec = importlib.util.find_spec(full)
+    assert spec is not None, f"could not find spec for {full!r}"
+    module = exec_module_from_spec(spec, full)
+
+    # The loader expects a `Plugin` class to be exported.
+    plugin_cls = getattr(module, "Plugin", None)
+    assert plugin_cls is not None, "qt module did not export a Plugin class"
+
+    print(f"[OK] external zip loads Plugin -> {plugin_cls!r}")
+    return 0
+
+
+if __name__ == "__main__":
+    if len(sys.argv) != 2:
+        print(__doc__)
+        sys.exit(2)
+    sys.exit(main(sys.argv[1]))