Merge pull request #8 from LazyImportsCabal/lazy_test

Lazy test

Lib/test/test_import/__init__.py

@@ -2558,6 +2558,26 @@ def test_basic_unused(self):
 
         self.assertFalse("test.test_import.data.lazy_imports.basic2" in sys.modules)
 
+    def test_basic_unused_use_externally(self):
+        try:
+            from test.test_import.data.lazy_imports import basic_unused
+        except ImportError as e:
+            self.fail('lazy import failed')
+
+        self.assertFalse("test.test_import.data.lazy_imports.basic2" in sys.modules)
+        x = basic_unused.test.test_import.data.lazy_imports.basic2
+        self.assertTrue("test.test_import.data.lazy_imports.basic2" in sys.modules)
+
+    def test_basic_from_unused_use_externally(self):
+        try:
+            from test.test_import.data.lazy_imports import basic_from_unused
+        except ImportError as e:
+            self.fail('lazy import failed')
+
+        self.assertFalse("test.test_import.data.lazy_imports.basic2" in sys.modules)
+        x = basic_from_unused.basic2
+        self.assertTrue("test.test_import.data.lazy_imports.basic2" in sys.modules)
+
     def test_basic_unused_dir(self):
         try:
             import test.test_import.data.lazy_imports.basic_unused
@@ -2758,6 +2778,19 @@ def test_lazy_import_pkg(self):
         self.assertTrue("test.test_import.data.lazy_imports.pkg" in sys.modules)
         self.assertTrue("test.test_import.data.lazy_imports.pkg.bar" in sys.modules)
 
+    def test_lazy_import_pkg_cross_import(self):
+        try:
+            import test.test_import.data.lazy_imports.pkg.c
+        except ImportError as e:
+            self.fail('lazy import failed')
+
+        self.assertTrue("test.test_import.data.lazy_imports.pkg" in sys.modules)
+        self.assertTrue("test.test_import.data.lazy_imports.pkg.c" in sys.modules)
+        self.assertFalse("test.test_import.data.lazy_imports.pkg.b" in sys.modules)
+
+        g = test.test_import.data.lazy_imports.pkg.c.get_globals()
+        self.assertEqual(type(g["x"]), int)
+        self.assertEqual(type(g["b"]), importlib.lazy_import)
 
 class TestSinglePhaseSnapshot(ModuleSnapshot):
     """A representation of a single-phase init module for testing.

Lib/test/test_import/data/lazy_imports/basic_from_unused.py

@@ -0,0 +1 @@
+lazy from test.test_import.data.lazy_imports import basic2

Lib/test/test_import/data/lazy_imports/pkg/b.py

@@ -0,0 +1,3 @@
+def foo():
+    return 'foo'
+

Lib/test/test_import/data/lazy_imports/pkg/c.py

@@ -0,0 +1,4 @@
+lazy from . import b, x
+
+def get_globals():
+    return globals()

Python/ceval.c

@@ -3304,6 +3304,22 @@ _PyEval_LazyImportFrom(PyThreadState *tstate, PyObject *v, PyObject *name)
     assert(name && PyUnicode_Check(name));
     PyObject *ret;
     PyLazyImportObject *d = (PyLazyImportObject *)v;
+    PyObject *mod = PyImport_GetModule(d->lz_from);
+    if (mod != NULL) {
+        // Check if the module already has the attribute, if so, resolve it eagerly.
+        if (PyModule_Check(mod)) {
+            PyObject *mod_dict = PyModule_GetDict(mod);
+            if (mod_dict != NULL) {
+                if (PyDict_GetItemRef(mod_dict, name, &ret) < 0) {
+                    return NULL;
+                } else if (ret != NULL) {
+                    return ret;
+                }
+            }
+        }
+        Py_DECREF(mod);
+    }
+
     if (d->lz_attr != NULL) {
         if (PyUnicode_Check(d->lz_attr)) {
             PyObject *from = PyUnicode_FromFormat("%U.%U", d->lz_from, d->lz_attr);

Python/import.c

@@ -4221,16 +4221,8 @@ _PyImport_LazyImportModuleLevelObject(PyThreadState *tstate,
     }
 
     PyInterpreterState *interp = tstate->interp;
-    _PyInterpreterFrame *frame = _PyEval_GetFrame();
     assert(frame->f_globals == frame->f_locals); // should only be called in global scope
 
-    PyObject *mod = PyImport_GetModule(abs_name);
-    bool already_exists = mod != NULL;
-    Py_XDECREF(mod);
-    if (mod != NULL) {
-        return PyImport_ImportModuleLevelObject(name, globals, locals, fromlist, level);
-    }
-
     // Check if the filter disables the lazy import
     PyObject *filter = LAZY_IMPORTS_FILTER(interp);
     if (filter != NULL) {
@@ -4262,7 +4254,7 @@ _PyImport_LazyImportModuleLevelObject(PyThreadState *tstate,
     }
 
     PyObject *res = _PyLazyImport_New(import_func, abs_name, fromlist);
-    if (!already_exists && register_lazy_on_parent(tstate, abs_name, import_func) < 0) {
+    if (register_lazy_on_parent(tstate, abs_name, import_func) < 0) {
         Py_DECREF(res);
         res = NULL;
     }