gh-152297: Reify dotted lazy imports with full name

Author: 1sgtpepper

Lib/test/test_lazy_import/__init__.py

@@ -167,6 +167,103 @@ def test_from_import_with_imported_module_getattr(self):
         """)
         assert_python_ok("-c", code)
 
+    @support.requires_subprocess()
+    def test_dotted_import_calls_full_name_import_hook(self):
+        """Dotted lazy imports should call __import__ with the full name."""
+        code = textwrap.dedent(r"""
+            import atexit
+            import builtins
+            import shutil
+            import sys
+            import tempfile
+            import types
+            from pathlib import Path
+
+            PKG = "hookpkg_gh_152297"
+            SUBMOD = f"{PKG}.sub"
+
+            real_import = builtins.__import__
+            full_name_calls = []
+            calls = []
+
+            tmpdir = tempfile.mkdtemp()
+            atexit.register(shutil.rmtree, tmpdir, ignore_errors=True)
+
+            package_dir = Path(tmpdir, PKG)
+            package_dir.mkdir()
+            (package_dir / "__init__.py").touch()
+            (package_dir / "sub.py").write_text(
+                "VALUE = 'real-submodule'\n", encoding="utf-8")
+
+            sys.path.insert(0, tmpdir)
+            atexit.register(setattr, builtins, "__import__", real_import)
+
+            def custom_import(name, globals=None, locals=None, fromlist=(),
+                              level=0):
+                caller = (
+                    globals.get("__name__")
+                    if isinstance(globals, dict) else None
+                )
+                call = (name, caller, tuple(fromlist or ()))
+                calls.append(call)
+
+                if name == SUBMOD:
+                    full_name_calls.append(call)
+                    package = real_import(PKG, globals, locals, (), level)
+                    module = types.ModuleType(SUBMOD)
+                    module.VALUE = "hooked-submodule"
+                    package.sub = module
+                    sys.modules[SUBMOD] = module
+                    return package
+
+                return real_import(name, globals, locals, fromlist, level)
+
+            builtins.__import__ = custom_import
+
+            lazy import hookpkg_gh_152297.sub
+
+            assert not full_name_calls, calls
+            assert hookpkg_gh_152297.sub.VALUE == "hooked-submodule", calls
+            assert full_name_calls == [(SUBMOD, "__main__", ())], calls
+        """)
+        assert_python_ok("-c", code)
+
+    @support.requires_subprocess()
+    def test_dotted_import_first_use_loads_full_target(self):
+        """First use of a dotted lazy import should load the submodule."""
+        code = textwrap.dedent(r"""
+            import atexit
+            import shutil
+            import sys
+            import tempfile
+            from pathlib import Path
+
+            PKG = "hookpkg_gh_152297_default"
+            SUBMOD = f"{PKG}.sub"
+
+            tmpdir = tempfile.mkdtemp()
+            atexit.register(shutil.rmtree, tmpdir, ignore_errors=True)
+
+            package_dir = Path(tmpdir, PKG)
+            package_dir.mkdir()
+            (package_dir / "__init__.py").touch()
+            (package_dir / "sub.py").write_text(
+                "VALUE = 42\n", encoding="utf-8")
+
+            sys.path.insert(0, tmpdir)
+
+            lazy import hookpkg_gh_152297_default.sub
+
+            assert SUBMOD not in sys.modules
+
+            _ = hookpkg_gh_152297_default
+
+            assert PKG in sys.modules
+            assert SUBMOD in sys.modules
+            assert hookpkg_gh_152297_default.sub.VALUE == 42
+        """)
+        assert_python_ok("-c", code)
+
 
 class GlobalLazyImportModeTests(LazyImportTestCase):
     """Tests for sys.set_lazy_imports() global mode control."""
@@ -658,14 +755,15 @@ class ErrorHandlingTests(LazyImportTestCase):
     """
 
     def test_import_error_shows_chained_traceback(self):
-        """Accessing a nonexistent lazy submodule via parent attr raises AttributeError."""
+        """A failed dotted lazy import should preserve the import failure."""
         code = textwrap.dedent("""
             import sys
             lazy import test.test_lazy_import.data.nonexistent_module
 
             try:
                 x = test.test_lazy_import.data.nonexistent_module
-            except AttributeError as e:
+            except ModuleNotFoundError as e:
+                assert e.__cause__ is not None, "Expected chained exception"
                 print("OK")
         """)
         result = subprocess.run(
@@ -710,20 +808,22 @@ def test_reification_retries_on_failure(self):
 
             lazy import test.test_lazy_import.data.broken_module
 
+            def lazy_proxy():
+                return globals()['test']
+
             # First access - should fail
             try:
                 x = test.test_lazy_import.data.broken_module
-            except AttributeError:
+            except ValueError:
                 pass
 
-            # The lazy object should still be a lazy proxy (not reified)
-            g = globals()
-            lazy_obj = g['test']
-            # The root 'test' binding should still allow retry
+            assert type(lazy_proxy()) is types.LazyImportType
+
             # Second access - should also fail (retry the import)
             try:
                 x = test.test_lazy_import.data.broken_module
-            except AttributeError:
+            except ValueError:
+                assert type(lazy_proxy()) is types.LazyImportType
                 print("OK - retry worked")
         """)
         result = subprocess.run(
@@ -743,7 +843,8 @@ def test_error_during_module_execution_propagates(self):
             try:
                 _ = test.test_lazy_import.data.broken_module
                 print("FAIL - should have raised")
-            except AttributeError:
+            except ValueError as e:
+                assert str(e) == "This module always fails to import"
                 print("OK")
         """)
         result = subprocess.run(

Lib/test/test_traceback.py

@@ -5609,24 +5609,43 @@ def _make_syntax_error(text, offset, end_offset):
 class TestLazyImportSuggestions(unittest.TestCase):
     """Test that lazy imports are not reified when computing AttributeError suggestions."""
 
+    @staticmethod
+    def _lazy_holder_script(body):
+        setup = textwrap.dedent("""
+            import atexit
+            import os
+            import shutil
+            import sys
+            import tempfile
+
+            tmpdir = tempfile.mkdtemp()
+            atexit.register(shutil.rmtree, tmpdir, ignore_errors=True)
+            with open(os.path.join(tmpdir, "lazy_traceback_bar.py"),
+                      "w", encoding="utf-8") as f:
+                f.write('print("BAR_MODULE_LOADED")\\n')
+            with open(os.path.join(tmpdir, "lazy_holder.py"),
+                      "w", encoding="utf-8") as f:
+                f.write("lazy import lazy_traceback_bar\\n")
+
+            sys.path.insert(0, tmpdir)
+            import lazy_holder
+        """)
+        return setup + textwrap.dedent(body)
+
     def test_attribute_error_does_not_reify_lazy_imports(self):
         """Printing an AttributeError should not trigger lazy import reification."""
-        # pkg.bar prints "BAR_MODULE_LOADED" when imported.
-        # If lazy import is reified during suggestion computation, we'll see it.
-        code = textwrap.dedent("""
-            lazy import test.test_lazy_import.data.pkg.bar
-            test.test_lazy_import.data.pkg.nonexistent
+        code = self._lazy_holder_script("""
+            lazy_holder.nonexistent
         """)
         rc, stdout, stderr = assert_python_failure('-c', code)
         self.assertNotIn(b"BAR_MODULE_LOADED", stdout)
 
     def test_traceback_formatting_does_not_reify_lazy_imports(self):
         """Formatting a traceback should not trigger lazy import reification."""
-        code = textwrap.dedent("""
+        code = self._lazy_holder_script("""
             import traceback
-            lazy import test.test_lazy_import.data.pkg.bar
             try:
-                test.test_lazy_import.data.pkg.nonexistent
+                lazy_holder.nonexistent
             except AttributeError:
                 traceback.format_exc()
             print("OK")
@@ -5637,10 +5656,8 @@ def test_traceback_formatting_does_not_reify_lazy_imports(self):
 
     def test_suggestion_still_works_for_non_lazy_attributes(self):
         """Suggestions should still work for non-lazy module attributes."""
-        code = textwrap.dedent("""
-            lazy import test.test_lazy_import.data.pkg.bar
-            # Typo for __name__
-            test.test_lazy_import.data.pkg.__nme__
+        code = self._lazy_holder_script("""
+            lazy_holder.__nme__
         """)
         rc, stdout, stderr = assert_python_failure('-c', code)
         self.assertIn(b"__name__", stderr)

Misc/NEWS.d/next/Core_and_Builtins/2026-06-26-23-40-24.gh-issue-152297.fhS3aw.rst

@@ -0,0 +1,2 @@
+Fix ``lazy import pkg.sub`` so reification calls ``__import__`` with
+``pkg.sub``, matching eager imports.

Python/import.c

@@ -3940,19 +3940,6 @@ _PyImport_LoadLazyImportTstate(PyThreadState *tstate, PyObject *lazy_import)
         goto error;
     }
 
-    Py_ssize_t dot = -1;
-    int full = 0;
-    if (lz->lz_attr != NULL) {
-        full = 1;
-    }
-    if (!full) {
-        dot = PyUnicode_FindChar(lz->lz_from, '.', 0,
-                                 PyUnicode_GET_LENGTH(lz->lz_from), 1);
-    }
-    if (dot < 0) {
-        full = 1;
-    }
-
     if (lz->lz_attr != NULL) {
         if (PyUnicode_Check(lz->lz_attr)) {
             fromlist = PyTuple_New(1);
@@ -3978,23 +3965,10 @@ _PyImport_LoadLazyImportTstate(PyThreadState *tstate, PyObject *lazy_import)
         PyErr_SetString(PyExc_ImportError, "__import__ not found");
         goto error;
     }
-    if (full) {
-        obj = _PyEval_ImportNameWithImport(
-            tstate, import_func, globals, globals,
-            lz->lz_from, fromlist, _PyLong_GetZero()
-        );
-    }
-    else {
-        PyObject *name = PyUnicode_Substring(lz->lz_from, 0, dot);
-        if (name == NULL) {
-            goto error;
-        }
-        obj = _PyEval_ImportNameWithImport(
-            tstate, import_func, globals, globals,
-            name, fromlist, _PyLong_GetZero()
-        );
-        Py_DECREF(name);
-    }
+    obj = _PyEval_ImportNameWithImport(
+        tstate, import_func, globals, globals,
+        lz->lz_from, fromlist, _PyLong_GetZero()
+    );
     if (obj == NULL) {
         goto error;
     }