1 files changed, 126 insertions, 0 deletions
diff --git a/tests/pylint/py2_compat.py b/tests/pylint/py2_compat.py
new file mode 100644
index 00000000..f3c4398c
--- /dev/null
+++ b/tests/pylint/py2_compat.py
@@ -0,0 +1,126 @@
+from __future__ import absolute_import
+
+import astroid
+
+from pylint.checkers import BaseChecker
+from pylint.interfaces import IAstroidChecker, HIGH
+
+from pylint.checkers import utils
+
+
+class Py2CompatibilityChecker(BaseChecker):
+    """Verify some simple properties of code compatible with both 2 and 3"""
+
+    __implements__ = IAstroidChecker
+
+    # The name defines a custom section of the config for this checker.
+    name = "py2-compat"
+    # The priority indicates the order that pylint will run the checkers.
+    priority = -1
+    # This class variable declares the messages (ie the warnings and errors)
+    # that the checker can emit.
+    msgs = {
+        # Each message has a code, a message that the user will see,
+        # a unique symbol that identifies the message,
+        # and a detailed help message
+        # that will be included in the documentation.
+        "E4200": ('Use explicit inheritance from "object"',
+                  "old-style-class",
+                  'Python 2 requires explicit inheritance from "object"'
+                  ' for new-style classes.'),
+        # old-division
+        # "E4210": ('Use "//" for integer division or import from "__future__"',
+        #     "division-without-import",
+        #     'Python 2 might perform integer division unless you import'
+        #     ' "division" from "__future__".'),
+        # no-absolute-import
+        # "E4211": ('Always import "absolute_import" from "__future__"',
+        #     "old-no-absolute-import",
+        #     'Python 2 allows relative imports unless you import'
+        #     ' "absolute_import" from "__future__".'),
+        "E4212": ('Import "print_function" from "__future__"',
+                  "print-without-import",
+                  'Python 2 requires importing "print_function" from'
+                  ' "__future__" to use the "print()" function syntax.'),
+        "E4220": ('Use explicit format spec numbering',
+                  "implicit-format-spec",
+                  'Python 2.6 does not support implicit format spec numbering'
+                  ' "{}", use explicit numbering "{0}" or keywords "{key}".')
+    }
+    # This class variable declares the options
+    # that are configurable by the user.
+    options = ()
+
+    def visit_classdef(self, node):
+        """Make sure classes explicitly inherit from object"""
+        if not node.bases and node.type == 'class' and not node.metaclass():
+            # We use confidence HIGH here because this message should only ever
+            # be emitted for classes at the root of the inheritance hierarchy
+            self.add_message('old-style-class', node=node, confidence=HIGH)
+
+    def visit_call(self, node):
+        """Make sure "print_function" is imported if necessary"""
+        if (isinstance(node.func, astroid.nodes.Name)
+                and node.func.name == "print"):
+            if "print_function" in node.root().future_imports:
+                def previous(node):
+                    if node is not None:
+                        parent = node.parent
+                    previous = node.previous_sibling()
+                    if previous is None:
+                        return parent
+                    return previous
+
+                prev = previous(node)
+                while prev is not None:
+                    if (isinstance(prev, astroid.nodes.ImportFrom)
+                        and prev.modname == "__future__"
+                        and "print_function" in (name_alias[0] for name_alias in
+                                                 prev.names)):
+                        return
+                    prev = previous(prev)
+
+                self.add_message("print-without-import", node=node,
+                                 confidence=HIGH)
+            else:
+                self.add_message("print-without-import", node=node,
+                                 confidence=HIGH)
+
+        func = utils.safe_infer(node.func)
+        if (
+            isinstance(func, astroid.BoundMethod)
+            and isinstance(func.bound, astroid.Instance)
+            and func.bound.name in ("str", "unicode", "bytes")
+        ):
+            if func.name == "format":
+                if isinstance(node.func, astroid.Attribute) and not isinstance(
+                    node.func.expr, astroid.Const
+                ):
+                    return
+                if node.starargs or node.kwargs:
+                    return
+                try:
+                    strnode = next(func.bound.infer())
+                except astroid.InferenceError:
+                    return
+                if not (isinstance(strnode, astroid.Const) and isinstance(
+                        strnode.value, str)):
+                    return
+                try:
+                    fields, num_args, manual_pos = (
+                        utils.parse_format_method_string(strnode.value)
+                    )
+                except utils.IncompleteFormatString:
+                    self.add_message("bad-format-string", node=node)
+                if num_args != 0:
+                    self.add_message("implicit-format-spec", node=node,
+                                     confidence=HIGH)
+
+
+def register(linter):
+    """This required method auto registers the checker.
+
+    :param linter: The linter to register the checker to.
+    :type linter: pylint.lint.PyLinter
+    """
+    linter.register_checker(Py2CompatibilityChecker(linter))