From 6df0b3e2a4381c64d4ca68c99d20b101b2b61fa7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Skytt=C3=A4?= <ville.skytta@iki.fi>
Date: Wed, 16 Oct 2019 22:11:35 +0300
Subject: [PATCH] Flag various collections as dangerous defaults (#3183)
 (#3194)

---
 ChangeLog                                     |  4 +++
 doc/whatsnew/2.5.rst                          |  2 ++
 pylint/checkers/base.py                       | 16 ++++++++--
 .../d/dangerous_default_value_py30.py         | 30 ++++++++++++++++++-
 .../d/dangerous_default_value_py30.txt        |  9 +++++-
 5 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 7ec37d5c43..b64a725cd4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -22,6 +22,10 @@ Release date: TBA
 
   Close #3190
 
+* Flag mutable ``collections.*`` utilities as dangerous defaults
+
+  Close #3183
+
 
 What's New in Pylint 2.4.3?
 ===========================
diff --git a/doc/whatsnew/2.5.rst b/doc/whatsnew/2.5.rst
index 6a075f635e..afd2dda873 100644
--- a/doc/whatsnew/2.5.rst
+++ b/doc/whatsnew/2.5.rst
@@ -30,3 +30,5 @@ Other Changes
   A pyproject.toml file must prepend section names with ``tool.pylint.``,
   for example ``[tool.pylint.'MESSAGES CONTROL']``.
   These files can also be passed in on the command line.
+
+* Mutable ``collections.*`` are now flagged as dangerous defaults.
diff --git a/pylint/checkers/base.py b/pylint/checkers/base.py
index bea58016d7..0906bf33f5 100644
--- a/pylint/checkers/base.py
+++ b/pylint/checkers/base.py
@@ -159,13 +159,25 @@ def get_regex(cls, name_type):
 # Name categories that are always consistent with all naming conventions.
 EXEMPT_NAME_CATEGORIES = {"exempt", "ignore"}
 
-# A mapping from builtin-qname -> symbol, to be used when generating messages
+# A mapping from qname -> symbol, to be used when generating messages
 # about dangerous default values as arguments
 DEFAULT_ARGUMENT_SYMBOLS = dict(
     zip(
         [".".join([BUILTINS, x]) for x in ("set", "dict", "list")],
         ["set()", "{}", "[]"],
-    )
+    ),
+    **{
+        x: "%s()" % x
+        for x in (
+            "collections.deque",
+            "collections.ChainMap",
+            "collections.Counter",
+            "collections.OrderedDict",
+            "collections.defaultdict",
+            "collections.UserDict",
+            "collections.UserList",
+        )
+    },
 )
 REVERSED_COMPS = {"<": ">", "<=": ">=", ">": "<", ">=": "<="}
 COMPARISON_OPERATORS = frozenset(("==", "!=", "<", ">", "<=", ">="))
diff --git a/tests/functional/d/dangerous_default_value_py30.py b/tests/functional/d/dangerous_default_value_py30.py
index 58a22f4434..9aab816350 100644
--- a/tests/functional/d/dangerous_default_value_py30.py
+++ b/tests/functional/d/dangerous_default_value_py30.py
@@ -1,5 +1,5 @@
 # pylint: disable=missing-docstring
-
+import collections
 
 HEHE = {}
 
@@ -77,3 +77,31 @@ def function15(value=INVALID_DICT): # [dangerous-default-value]
 def function16(value={1}): # [dangerous-default-value]
     """set literal as default value"""
     return value
+
+def function17(value=collections.deque()):  # [dangerous-default-value]
+    """mutable, dangerous"""
+    return value
+
+def function18(value=collections.ChainMap()):  # [dangerous-default-value]
+    """mutable, dangerous"""
+    return value
+
+def function19(value=collections.Counter()):  # [dangerous-default-value]
+    """mutable, dangerous"""
+    return value
+
+def function20(value=collections.OrderedDict()):  # [dangerous-default-value]
+    """mutable, dangerous"""
+    return value
+
+def function21(value=collections.defaultdict()):  # [dangerous-default-value]
+    """mutable, dangerous"""
+    return value
+
+def function22(value=collections.UserDict()):  # [dangerous-default-value]
+    """mutable, dangerous"""
+    return value
+
+def function23(value=collections.UserList()):  # [dangerous-default-value]
+    """mutable, dangerous"""
+    return value
diff --git a/tests/functional/d/dangerous_default_value_py30.txt b/tests/functional/d/dangerous_default_value_py30.txt
index 7571c00f7c..40caaf5a33 100644
--- a/tests/functional/d/dangerous_default_value_py30.txt
+++ b/tests/functional/d/dangerous_default_value_py30.txt
@@ -11,4 +11,11 @@ dangerous-default-value:52:function12:Dangerous default value dict() (builtins.d
 dangerous-default-value:61:function13:Dangerous default value OINK (builtins.dict) as argument
 dangerous-default-value:65:function14:Dangerous default value dict() (builtins.dict) as argument
 dangerous-default-value:73:function15:Dangerous default value INVALID_DICT (builtins.dict) as argument
-dangerous-default-value:77:function16:Dangerous default value set() as argument
\ No newline at end of file
+dangerous-default-value:77:function16:Dangerous default value set() as argument
+dangerous-default-value:81:function17:Dangerous default value deque() (collections.deque) as argument
+dangerous-default-value:85:function18:Dangerous default value ChainMap() (collections.ChainMap) as argument
+dangerous-default-value:89:function19:Dangerous default value Counter() (collections.Counter) as argument
+dangerous-default-value:93:function20:Dangerous default value OrderedDict() (collections.OrderedDict) as argument
+dangerous-default-value:97:function21:Dangerous default value defaultdict() (collections.defaultdict) as argument
+dangerous-default-value:101:function22:Dangerous default value UserDict() (collections.UserDict) as argument
+dangerous-default-value:105:function23:Dangerous default value UserList() (collections.UserList) as argument