Importation classes with imported name and alias

In order to solve many corner cases related to imports,
more information is needed about each import.

This change creates two new classes:
- SubmoduleImportation
- ImportationFrom

And adds an optional parameter full_name to the super class
Importation.

Functionally, this change only improves existing error messages
to report the full imported name where previously an error
would include only the import alias.

2 files changed, 183 insertions, 10 deletions

diff --git a/pyflakes/checker.py b/pyflakes/checker.py
index 7155b54..76dc137 100644
--- a/pyflakes/checker.py
+++ b/pyflakes/checker.py
@@ -136,16 +136,83 @@ class Importation(Definition):
     @type fullName: C{str}
     """
 
-    def __init__(self, name, source):
-        self.fullName = name
+    def __init__(self, name, source, full_name=None):
+        self.fullName = full_name or name
         self.redefined = []
-        name = name.split('.')[0]
         super(Importation, self).__init__(name, source)
 
     def redefines(self, other):
+        return isinstance(other, Definition) and self.name == other.name
+
+    def _has_alias(self):
+        """Return whether importation needs an as clause."""
+        return not self.fullName.split('.')[-1] == self.name
+
+    @property
+    def source_statement(self):
+        """Generate a source statement equivalent to the import."""
+        if self._has_alias():
+            return 'import %s as %s' % (self.fullName, self.name)
+        else:
+            return 'import %s' % self.fullName
+
+    def __str__(self):
+        """Return import full name with alias."""
+        if self._has_alias():
+            return self.fullName + ' as ' + self.name
+        else:
+            return self.fullName
+
+
+class SubmoduleImportation(Importation):
+
+    def __init__(self, name, source):
+        # A dot should only appear in the name when it is a submodule import
+        # without an 'as' clause, which is a special type of import where the
+        # root module is implicitly imported, and the submodules are also
+        # accessible because Python does not restrict which attributes of the
+        # root module may be used.
+        assert '.' in name and (not source or isinstance(source, ast.Import))
+        package_name = name.split('.')[0]
+        super(SubmoduleImportation, self).__init__(package_name, source)
+        self.fullName = name
+
+    def redefines(self, other):
         if isinstance(other, Importation):
             return self.fullName == other.fullName
-        return isinstance(other, Definition) and self.name == other.name
+        return super(SubmoduleImportation, self).redefines(other)
+
+    def __str__(self):
+        return self.fullName
+
+    @property
+    def source_statement(self):
+        return 'import ' + self.fullName
+
+
+class ImportationFrom(Importation):
+
+    def __init__(self, name, source, module, real_name=None):
+        self.module = module
+        self.real_name = real_name or name
+        full_name = module + '.' + self.real_name
+        super(ImportationFrom, self).__init__(name, source, full_name)
+
+    def __str__(self):
+        """Return import full name with alias."""
+        if self.real_name != self.name:
+            return self.fullName + ' as ' + self.name
+        else:
+            return self.fullName
+
+    @property
+    def source_statement(self):
+        if self.real_name != self.name:
+            return 'from %s import %s as %s' % (self.module,
+                                                self.real_name,
+                                                self.name)
+        else:
+            return 'from %s import %s' % (self.module, self.name)
 
 
 class StarImportation(Importation):
@@ -158,8 +225,15 @@ class StarImportation(Importation):
         self.name = name + '.*'
         self.fullName = name
 
+    @property
+    def source_statement(self):
+        return 'from ' + self.fullName + ' import *'
 
-class FutureImportation(Importation):
+    def __str__(self):
+        return self.name
+
+
+class FutureImportation(ImportationFrom):
     """
     A binding created by a from `__future__` import statement.
 
@@ -167,7 +241,7 @@ class FutureImportation(Importation):
     """
 
     def __init__(self, name, source, scope):
-        super(FutureImportation, self).__init__(name, source)
+        super(FutureImportation, self).__init__(name, source, '__future__')
         self.used = (scope, source)
 
 
@@ -430,7 +504,7 @@ class Checker(object):
                     used = value.used or value.name in all_names
                     if not used:
                         messg = messages.UnusedImport
-                        self.report(messg, value.source, value.name)
+                        self.report(messg, value.source, str(value))
                     for node in value.redefined:
                         if isinstance(self.getParent(node), ast.For):
                             messg = messages.ImportShadowedByLoopVar
@@ -1039,8 +1113,11 @@ class Checker(object):
 
     def IMPORT(self, node):
         for alias in node.names:
-            name = alias.asname or alias.name
-            importation = Importation(name, node)
+            if '.' in alias.name and not alias.asname:
+                importation = SubmoduleImportation(alias.name, node)
+            else:
+                name = alias.asname or alias.name
+                importation = Importation(name, node, alias.name)
             self.addBinding(node, importation)
 
     def IMPORTFROM(self, node):
@@ -1069,7 +1146,8 @@ class Checker(object):
                 self.report(messages.ImportStarUsed, node, node.module)
                 importation = StarImportation(node.module, node)
             else:
-                importation = Importation(name, node)
+                importation = ImportationFrom(name, node,
+                                              node.module, alias.name)
             self.addBinding(node, importation)
 
     def TRY(self, node):
diff --git a/pyflakes/test/test_imports.py b/pyflakes/test/test_imports.py
index 2101579..41a0e07 100644
--- a/pyflakes/test/test_imports.py
+++ b/pyflakes/test/test_imports.py
@@ -2,9 +2,75 @@
 from sys import version_info
 
 from pyflakes import messages as m
+from pyflakes.checker import (
+    FutureImportation,
+    Importation,
+    ImportationFrom,
+    StarImportation,
+    SubmoduleImportation,
+)
 from pyflakes.test.harness import TestCase, skip, skipIf
 
 
+class TestImportationObject(TestCase):
+
+    def test_import_basic(self):
+        binding = Importation('a', None, 'a')
+        assert binding.source_statement == 'import a'
+        assert str(binding) == 'a'
+
+    def test_import_as(self):
+        binding = Importation('c', None, 'a')
+        assert binding.source_statement == 'import a as c'
+        assert str(binding) == 'a as c'
+
+    def test_import_submodule(self):
+        binding = SubmoduleImportation('a.b', None)
+        assert binding.source_statement == 'import a.b'
+        assert str(binding) == 'a.b'
+
+    def test_import_submodule_as(self):
+        # A submodule import with an as clause is not a SubmoduleImportation
+        binding = Importation('c', None, 'a.b')
+        assert binding.source_statement == 'import a.b as c'
+        assert str(binding) == 'a.b as c'
+
+    def test_import_submodule_as_source_name(self):
+        binding = Importation('a', None, 'a.b')
+        assert binding.source_statement == 'import a.b as a'
+        assert str(binding) == 'a.b as a'
+
+    def test_importfrom_member(self):
+        binding = ImportationFrom('b', None, 'a', 'b')
+        assert binding.source_statement == 'from a import b'
+        assert str(binding) == 'a.b'
+
+    def test_importfrom_submodule_member(self):
+        binding = ImportationFrom('c', None, 'a.b', 'c')
+        assert binding.source_statement == 'from a.b import c'
+        assert str(binding) == 'a.b.c'
+
+    def test_importfrom_member_as(self):
+        binding = ImportationFrom('c', None, 'a', 'b')
+        assert binding.source_statement == 'from a import b as c'
+        assert str(binding) == 'a.b as c'
+
+    def test_importfrom_submodule_member_as(self):
+        binding = ImportationFrom('d', None, 'a.b', 'c')
+        assert binding.source_statement == 'from a.b import c as d'
+        assert str(binding) == 'a.b.c as d'
+
+    def test_importfrom_star(self):
+        binding = StarImportation('a.b', None)
+        assert binding.source_statement == 'from a.b import *'
+        assert str(binding) == 'a.b.*'
+
+    def test_importfrom_future(self):
+        binding = FutureImportation('print_function', None, None)
+        assert binding.source_statement == 'from __future__ import print_function'
+        assert str(binding) == '__future__.print_function'
+
+
 class Test(TestCase):
 
     def test_unusedImport(self):
@@ -17,6 +83,12 @@ class Test(TestCase):
         self.flakes('from moo import fu as FU, bar as FU',
                     m.RedefinedWhileUnused, m.UnusedImport)
 
+    def test_aliasedImportShadowModule(self):
+        """Imported aliases can shadow the source of the import."""
+        self.flakes('from moo import fu as moo; moo')
+        self.flakes('import fu as fu; fu')
+        self.flakes('import fu.bar as fu; fu')
+
     def test_usedImport(self):
         self.flakes('import fu; print(fu)')
         self.flakes('from baz import fu; print(fu)')
@@ -685,6 +757,29 @@ class Test(TestCase):
         fu.bar, fu.baz
         ''')
 
+    def test_used_package_with_submodule_import(self):
+        """
+        Usage of package marks submodule imports as used.
+        """
+        self.flakes('''
+        import fu
+        import fu.bar
+        fu.x
+        ''')
+
+    def test_unused_package_with_submodule_import(self):
+        """
+        When a package and its submodule are imported, only report once.
+        """
+        checker = self.flakes('''
+        import fu
+        import fu.bar
+        ''', m.UnusedImport)
+        error = checker.messages[0]
+        assert error.message == '%r imported but unused'
+        assert error.message_args == ('fu.bar', )
+        assert error.lineno == 5 if self.withDoctest else 3
+
     def test_assignRHSFirst(self):
         self.flakes('import fu; fu = fu')
         self.flakes('import fu; fu, bar = fu')