Expand tests and fix bugs in packaging.util.resolve_name.

The code is still ugly, but at least it works better now.  Patches to
make it easier to read are welcome, as well as support in #12915.

Lib/packaging/tests/test_util.py

@@ -4,6 +4,7 @@ import sys
 import time
 import logging
 import tempfile
+import textwrap
 import subprocess
 from io import StringIO
 
@@ -375,35 +376,48 @@ class UtilTestCase(support.EnvironRestorer,
                                         'pkg1.pkg3.pkg6']))
 
     def test_resolve_name(self):
-        self.assertIs(str, resolve_name('builtins.str'))
+        # test raw module name
-        self.assertEqual(
+        tmpdir = self.mkdtemp()
-            UtilTestCase.__name__,
+        sys.path.append(tmpdir)
-            resolve_name("packaging.tests.test_util.UtilTestCase").__name__)
+        self.addCleanup(sys.path.remove, tmpdir)
-        self.assertEqual(
+        self.write_file((tmpdir, 'hello.py'), '')
-            UtilTestCase.test_resolve_name.__name__,
-            resolve_name("packaging.tests.test_util.UtilTestCase."
-                         "test_resolve_name").__name__)
 
-        self.assertRaises(ImportError, resolve_name,
+        os.makedirs(os.path.join(tmpdir, 'a', 'b'))
-                          "packaging.tests.test_util.UtilTestCaseNot")
+        self.write_file((tmpdir, 'a', '__init__.py'), '')
-        self.assertRaises(ImportError, resolve_name,
+        self.write_file((tmpdir, 'a', 'b', '__init__.py'), '')
-                          "packaging.tests.test_util.UtilTestCase."
+        self.write_file((tmpdir, 'a', 'b', 'c.py'), 'class Foo: pass')
-                          "nonexistent_attribute")
+        self.write_file((tmpdir, 'a', 'b', 'd.py'), textwrap.dedent("""\
+                         class FooBar:
+                             class Bar:
+                                 def baz(self):
+                                     pass
+                            """))
 
-    def test_import_nested_first_time(self):
+        # check Python, C and built-in module
-        tmp_dir = self.mkdtemp()
+        self.assertEqual(resolve_name('hello').__name__, 'hello')
-        os.makedirs(os.path.join(tmp_dir, 'a', 'b'))
+        self.assertEqual(resolve_name('_csv').__name__, '_csv')
-        self.write_file(os.path.join(tmp_dir, 'a', '__init__.py'), '')
+        self.assertEqual(resolve_name('sys').__name__, 'sys')
-        self.write_file(os.path.join(tmp_dir, 'a', 'b', '__init__.py'), '')
-        self.write_file(os.path.join(tmp_dir, 'a', 'b', 'c.py'),
-                                    'class Foo: pass')
 
-        try:
+        # test module.attr
-            sys.path.append(tmp_dir)
+        self.assertIs(resolve_name('builtins.str'), str)
-            resolve_name("a.b.c.Foo")
+        self.assertIsNone(resolve_name('hello.__doc__'))
-            # assert nothing raised
+        self.assertEqual(resolve_name('a.b.c.Foo').__name__, 'Foo')
-        finally:
+        self.assertEqual(resolve_name('a.b.d.FooBar.Bar.baz').__name__, 'baz')
-            sys.path.remove(tmp_dir)
+
+        # error if module not found
+        self.assertRaises(ImportError, resolve_name, 'nonexistent')
+        self.assertRaises(ImportError, resolve_name, 'non.existent')
+        self.assertRaises(ImportError, resolve_name, 'a.no')
+        self.assertRaises(ImportError, resolve_name, 'a.b.no')
+        self.assertRaises(ImportError, resolve_name, 'a.b.no.no')
+        self.assertRaises(ImportError, resolve_name, 'inva-lid')
+
+        # looking up built-in names is not supported
+        self.assertRaises(ImportError, resolve_name, 'str')
+
+        # error if module found but not attr
+        self.assertRaises(ImportError, resolve_name, 'a.b.Spam')
+        self.assertRaises(ImportError, resolve_name, 'a.b.c.Spam')
 
     def test_run_2to3_on_code(self):
         content = "print 'test'"

Lib/packaging/util.py

@@ -630,22 +630,35 @@ def find_packages(paths=(os.curdir,), exclude=()):
 def resolve_name(name):
     """Resolve a name like ``module.object`` to an object and return it.
 
-    Raise ImportError if the module or name is not found.
+    This functions supports packages and attributes without depth limitation:
+    ``package.package.module.class.class.function.attr`` is valid input.
+    However, looking up builtins is not directly supported: use
+    ``builtins.name``.
+
+    Raises ImportError if importing the module fails or if one requested
+    attribute is not found.
     """
+    if '.' not in name:
+        # shortcut
+        __import__(name)
+        return sys.modules[name]
+
+    # FIXME clean up this code!
     parts = name.split('.')
     cursor = len(parts)
     module_name = parts[:cursor]
+    ret = ''
 
     while cursor > 0:
         try:
             ret = __import__('.'.join(module_name))
             break
         except ImportError:
-            if cursor == 0:
-                raise
             cursor -= 1
             module_name = parts[:cursor]
-            ret = ''
+
+    if ret == '':
+        raise ImportError(parts[0])
 
     for part in parts[1:]:
         try: