Introduced DeprecatedMixin

5 files changed, 166 insertions, 34 deletions

diff --git a/ChangeLog b/ChangeLog
index ed2e2398d..8c8a83153 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -5,6 +5,10 @@ Pylint's ChangeLog
 What's New in Pylint 2.7.0?
 ===========================
 
+* Introduce DeprecationMixin for reusable deprecation checks.
+
+  Closes #4049
+
 * Fix false positive for ``builtin-not-iterating`` when ``map`` receives iterable
 
   Closes #4078
diff --git a/pylint/checkers/__init__.py b/pylint/checkers/__init__.py
index 31d2df522..b459b0497 100644
--- a/pylint/checkers/__init__.py
+++ b/pylint/checkers/__init__.py
@@ -44,6 +44,7 @@ messages nor reports. XXX not true, emit a 07 report !
 """
 
 from pylint.checkers.base_checker import BaseChecker, BaseTokenChecker
+from pylint.checkers.deprecated import DeprecatedMixin
 from pylint.checkers.mapreduce_checker import MapReduceMixin
 from pylint.utils import register_plugins
 
@@ -71,5 +72,6 @@ __all__ = [
     "BaseTokenChecker",
     "initialize",
     "MapReduceMixin",
+    "DeprecatedMixin",
     "register_plugins",
 ]
diff --git a/pylint/checkers/deprecated.py b/pylint/checkers/deprecated.py
new file mode 100644
index 000000000..0bbad05ee
--- /dev/null
+++ b/pylint/checkers/deprecated.py
@@ -0,0 +1,49 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/master/COPYING
+
+"""Checker mixin for deprecated functionality."""
+
+import abc
+
+import astroid
+
+ACCEPTABLE_NODES = (
+    astroid.BoundMethod,
+    astroid.UnboundMethod,
+    astroid.FunctionDef,
+)
+
+
+class DeprecatedMixin(metaclass=abc.ABCMeta):
+    """A mixin implementing logic for checking deprecated symbols.
+    A class imlementing mixin must define "deprecated-method" Message.
+    """
+
+    @abc.abstractmethod
+    def deprecated_methods(self):
+        """Callback returning the deprecated methods/functions.
+
+        Returns:
+            collections.abc.Container of deprecated function/method names.
+        """
+
+    def check_deprecated_method(self, node, inferred):
+        """Executes the checker for the given node. This method should
+        be called from the checker implementing this mixin.
+        """
+
+        # Reject nodes which aren't of interest to us.
+        if not isinstance(inferred, ACCEPTABLE_NODES):
+            return
+
+        if isinstance(node.func, astroid.Attribute):
+            func_name = node.func.attrname
+        elif isinstance(node.func, astroid.Name):
+            func_name = node.func.name
+        else:
+            # Not interested in other nodes.
+            return
+
+        qname = inferred.qname()
+        if any(name in self.deprecated_methods() for name in (qname, func_name)):
+            self.add_message("deprecated-method", node=node, args=(func_name,))
diff --git a/pylint/checkers/stdlib.py b/pylint/checkers/stdlib.py
index 270623f09..ad6e4f855 100644
--- a/pylint/checkers/stdlib.py
+++ b/pylint/checkers/stdlib.py
@@ -36,7 +36,7 @@ import astroid
 from astroid.bases import Instance
 from astroid.node_classes import Const
 
-from pylint.checkers import BaseChecker, utils
+from pylint.checkers import BaseChecker, DeprecatedMixin, utils
 from pylint.interfaces import IAstroidChecker
 
 OPEN_FILES = {"open", "file"}
@@ -80,7 +80,7 @@ def _check_mode_str(mode):
     return True
 
 
-class StdlibChecker(BaseChecker):
+class StdlibChecker(BaseChecker, DeprecatedMixin):
     __implements__ = (IAstroidChecker,)
     name = "stdlib"
 
@@ -336,7 +336,7 @@ class StdlibChecker(BaseChecker):
                         self._check_env_function(node, inferred)
                     elif name == SUBPROCESS_RUN:
                         self._check_for_check_kw_in_run(node)
-                self._check_deprecated_method(node, inferred)
+                self.check_deprecated_method(node, inferred)
         except astroid.InferenceError:
             return
 
@@ -358,37 +358,6 @@ class StdlibChecker(BaseChecker):
         for value in node.values:
             self._check_datetime(value)
 
-    def _check_deprecated_method(self, node, inferred):
-        py_vers = sys.version_info[0]
-
-        if isinstance(node.func, astroid.Attribute):
-            func_name = node.func.attrname
-        elif isinstance(node.func, astroid.Name):
-            func_name = node.func.name
-        else:
-            # Not interested in other nodes.
-            return
-
-        # Reject nodes which aren't of interest to us.
-        acceptable_nodes = (
-            astroid.BoundMethod,
-            astroid.UnboundMethod,
-            astroid.FunctionDef,
-        )
-        if not isinstance(inferred, acceptable_nodes):
-            return
-
-        qname = inferred.qname()
-        if any(name in self.deprecated[0] for name in (qname, func_name)):
-            self.add_message("deprecated-method", node=node, args=(func_name,))
-        else:
-            for since_vers, func_list in self.deprecated[py_vers].items():
-                if since_vers <= sys.version_info and any(
-                    name in func_list for name in (qname, func_name)
-                ):
-                    self.add_message("deprecated-method", node=node, args=(func_name,))
-                    break
-
     def _check_redundant_assert(self, node, infer):
         if (
             isinstance(infer, astroid.BoundMethod)
@@ -481,6 +450,15 @@ class StdlibChecker(BaseChecker):
         else:
             self.add_message(message, node=node, args=(name, call_arg.pytype()))
 
+    def deprecated_methods(self):
+        py_vers = sys.version_info[0]
+        deprecated_methods = set()
+        deprecated_methods.update(self.deprecated[0])
+        for since_vers, func_list in self.deprecated[py_vers].items():
+            if since_vers <= sys.version_info:
+                deprecated_methods.update(func_list)
+        return deprecated_methods
+
 
 def register(linter):
     """required method to auto register this checker """
diff --git a/tests/checkers/unittest_deprecated.py b/tests/checkers/unittest_deprecated.py
new file mode 100644
index 000000000..e4da246ff
--- /dev/null
+++ b/tests/checkers/unittest_deprecated.py
@@ -0,0 +1,99 @@
+import astroid
+
+from pylint.checkers import BaseChecker, DeprecatedMixin, utils
+from pylint.interfaces import UNDEFINED, IAstroidChecker
+from pylint.testutils import CheckerTestCase, Message
+
+
+class _DeprecatedChecker(BaseChecker, DeprecatedMixin):
+    __implements__ = (IAstroidChecker,)
+    name = "deprecated"
+
+    msgs = {
+        "W1505": (
+            "Using deprecated method %s()",
+            "deprecated-method",
+            "The method is marked as deprecated and will be removed in "
+            "a future version of Python. Consider looking for an "
+            "alternative in the documentation.",
+        )
+    }
+
+    @utils.check_messages(
+        "deprecated-method",
+    )
+    def visit_call(self, node):
+        """Visit a Call node."""
+        try:
+            for inferred in node.func.infer():
+                self.check_deprecated_method(node, inferred)
+        except astroid.InferenceError:
+            return
+
+    def deprecated_methods(self):
+        return {"deprecated_func", ".Deprecated.deprecated_method"}
+
+
+class TestDeprecatedChecker(CheckerTestCase):
+    CHECKER_CLASS = _DeprecatedChecker
+
+    def test_deprecated_function(self):
+        # Tests detecting deprecated function
+        node = astroid.extract_node(
+            """
+        def deprecated_func():
+            pass
+
+        deprecated_func()
+        """
+        )
+        with self.assertAddsMessages(
+            Message(
+                msg_id="deprecated-method",
+                args=("deprecated_func",),
+                node=node,
+                confidence=UNDEFINED,
+            )
+        ):
+            self.checker.visit_call(node)
+
+    def test_deprecated_method(self):
+        # Tests detecting deprecated method
+        node = astroid.extract_node(
+            """
+        class Deprecated:
+            def deprecated_method():
+                pass
+
+        d = Deprecated()
+        d.deprecated_method()
+        """
+        )
+        with self.assertAddsMessages(
+            Message(
+                msg_id="deprecated-method",
+                args=("deprecated_method",),
+                node=node,
+                confidence=UNDEFINED,
+            )
+        ):
+            self.checker.visit_call(node)
+
+    def test_no_message(self):
+        # Tests not raising error when no deprecated functions/methods are present.
+        node = astroid.extract_node(
+            """
+        class MyClass:
+            def mymethod():
+                pass
+
+        MyClass().mymethod()
+
+        def myfunc():
+            pass
+
+        myfunc()
+        """
+        )
+        with self.assertNoMessages():
+            self.checker.visit_call(node)