Adding implicit-str-concat-in-sequence check (#1655)

``implicit-str-concat-in-sequence`` detects string concatenation inside lists, sets & tuples. It would warn on code such as `('a', 'b' 'c')`.
pylint-dev · Oct 10, 2018 · fcc0151 · fcc0151
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diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
@@ -243,3 +243,5 @@ contributors:
 * Scott Worley: contributor
 
 * Michael Hudson-Doyle
+
+* Lucas Cimon: contributor
diff --git a/ChangeLog b/ChangeLog
@@ -167,6 +167,8 @@ Release date: TBA
      Close #1422
      Close #2019
 
+   * Add a new check 'implicit-str-concat-in-sequence' to spot string concatenation inside lists, sets & tuples.
+
 What's New in Pylint 2.1.1?
 ===========================
 

diff --git a/doc/whatsnew/2.2.rst b/doc/whatsnew/2.2.rst
@@ -20,6 +20,15 @@ New checkers
 * ``logging-format-style`` is a new option for the logging checker for usage of
   str.format() style format strings in calls to loggers.
 
+* ``implicit-str-concat-in-sequence`` detects string concatenation inside lists, sets & tuples.
+
+  Example of code that would generate such warning:
+
+  .. code-block:: python
+
+    woops = ('a', 'b' 'c')
+
+
 Other Changes
 =============
 

diff --git a/pylint/checkers/base.py b/pylint/checkers/base.py
@@ -448,12 +448,12 @@ class BasicErrorChecker(_BasicChecker):
         "E0104": (
             "Return outside function",
             "return-outside-function",
-            'Used when a "return" statement is found outside a function or ' "method.",
+            'Used when a "return" statement is found outside a function or method.',
         ),
         "E0105": (
             "Yield outside function",
             "yield-outside-function",
-            'Used when a "yield" statement is found outside a function or ' "method.",
+            'Used when a "yield" statement is found outside a function or method.',
         ),
         "E0106": (
             "Return with argument inside generator",
@@ -472,7 +472,7 @@ class BasicErrorChecker(_BasicChecker):
         "E0108": (
             "Duplicate argument name %s in function definition",
             "duplicate-argument-name",
-            "Duplicate argument names in function definitions are syntax" " errors.",
+            "Duplicate argument names in function definitions are syntax errors.",
         ),
         "E0110": (
             "Abstract class %r with abstract methods instantiated",
@@ -496,12 +496,12 @@ class BasicErrorChecker(_BasicChecker):
         "E0113": (
             "Starred assignment target must be in a list or tuple",
             "invalid-star-assignment-target",
-            "Emitted when a star expression is used as a starred " "assignment target.",
+            "Emitted when a star expression is used as a starred assignment target.",
         ),
         "E0114": (
             "Can use starred expression only in assignment target",
             "star-needs-assignment-target",
-            "Emitted when a star expression is not used in an " "assignment target.",
+            "Emitted when a star expression is not used in an assignment target.",
         ),
         "E0115": (
             "Name %r is nonlocal and global",
@@ -896,7 +896,7 @@ class BasicChecker(_BasicChecker):
         "W0104": (
             "Statement seems to have no effect",
             "pointless-statement",
-            "Used when a statement doesn't have (or at least seems to) " "any effect.",
+            "Used when a statement doesn't have (or at least seems to) any effect.",
         ),
         "W0105": (
             "String statement has no effect",
@@ -923,7 +923,7 @@ class BasicChecker(_BasicChecker):
         "W0109": (
             "Duplicate key %r in dictionary",
             "duplicate-key",
-            "Used when a dictionary expression binds the same key multiple " "times.",
+            "Used when a dictionary expression binds the same key multiple times.",
         ),
         "W0122": (
             "Use of exec",
@@ -1533,7 +1533,7 @@ class NameChecker(_BasicChecker):
         "C0102": (
             'Black listed name "%s"',
             "blacklisted-name",
-            "Used when the name is listed in the black list (unauthorized " "names).",
+            "Used when the name is listed in the black list (unauthorized names).",
         ),
         "C0103": (
             '%s name "%s" doesn\'t conform to %s',
@@ -1975,7 +1975,7 @@ class PassChecker(_BasicChecker):
         "W0107": (
             "Unnecessary pass statement",
             "unnecessary-pass",
-            'Used when a "pass" statement that can be avoided is ' "encountered.",
+            'Used when a "pass" statement that can be avoided is encountered.',
         )
     }
 

diff --git a/pylint/checkers/classes.py b/pylint/checkers/classes.py
@@ -459,12 +459,12 @@ def _has_same_layout_slots(slots, assigned_value):
     "E0203": (
         "Access to member %r before its definition line %s",
         "access-member-before-definition",
-        "Used when an instance member is accessed before it's actually " "assigned.",
+        "Used when an instance member is accessed before it's actually assigned.",
     ),
     "W0201": (
         "Attribute %r defined outside __init__",
         "attribute-defined-outside-init",
-        "Used when an instance attribute is defined outside the __init__ " "method.",
+        "Used when an instance attribute is defined outside the __init__ method.",
     ),
     "W0212": (
         "Access to a protected member %s of a client class",  # E0214
@@ -550,7 +550,7 @@ def _has_same_layout_slots(slots, assigned_value):
     "W0232": (
         "Class has no __init__ method",
         "no-init",
-        "Used when a class has no __init__ method, neither its parent " "classes.",
+        "Used when a class has no __init__ method, neither its parent classes.",
     ),
     "W0233": (
         "__init__ method from a non direct base class %r is called",
@@ -566,14 +566,14 @@ def _has_same_layout_slots(slots, assigned_value):
         "from the MRO.",
     ),
     "E0236": (
-        "Invalid object %r in __slots__, must contain " "only non empty strings",
+        "Invalid object %r in __slots__, must contain only non empty strings",
         "invalid-slots-object",
         "Used when an invalid (non-string) object occurs in __slots__.",
     ),
     "E0237": (
         "Assigning to attribute %r not defined in class slots",
         "assigning-non-slot",
-        "Used when assigning to an attribute not defined " "in the class slots.",
+        "Used when assigning to an attribute not defined in the class slots.",
     ),
     "E0238": (
         "Invalid __slots__ object",
@@ -584,7 +584,7 @@ def _has_same_layout_slots(slots, assigned_value):
     "E0239": (
         "Inheriting %r, which is not a class.",
         "inherit-non-class",
-        "Used when a class inherits from something which is not a " "class.",
+        "Used when a class inherits from something which is not a class.",
     ),
     "E0240": (
         "Inconsistent method resolution order for class %r",
@@ -599,17 +599,17 @@ def _has_same_layout_slots(slots, assigned_value):
     "R0202": (
         "Consider using a decorator instead of calling classmethod",
         "no-classmethod-decorator",
-        "Used when a class method is defined without using the decorator " "syntax.",
+        "Used when a class method is defined without using the decorator syntax.",
     ),
     "R0203": (
         "Consider using a decorator instead of calling staticmethod",
         "no-staticmethod-decorator",
-        "Used when a static method is defined without using the decorator " "syntax.",
+        "Used when a static method is defined without using the decorator syntax.",
     ),
     "C0205": (
         "Class __slots__ should be a non-string iterable",
         "single-string-used-for-slots",
-        "Used when a class __slots__ is a simple string, rather " "than an iterable.",
+        "Used when a class __slots__ is a simple string, rather than an iterable.",
     ),
     "R0205": (
         "Class %r inherits from object, can be safely removed from bases in python3",

diff --git a/pylint/checkers/design_analysis.py b/pylint/checkers/design_analysis.py
@@ -86,7 +86,7 @@
     "R0916": (
         "Too many boolean expressions in if statement (%s/%s)",
         "too-many-boolean-expressions",
-        "Used when an if statement contains too many boolean " "expressions.",
+        "Used when an if statement contains too many boolean expressions.",
     ),
 }
 SPECIAL_OBJ = re.compile("^_{2}[a-z]+_{2}$")

diff --git a/pylint/checkers/exceptions.py b/pylint/checkers/exceptions.py
@@ -88,7 +88,7 @@ def _is_raising(body: typing.List) -> bool:
         "string is raised (i.e. a `TypeError` will be raised).",
     ),
     "E0703": (
-        "Exception context set to something which is not an " "exception, nor None",
+        "Exception context set to something which is not an exception, nor None",
         "bad-exception-context",
         'Used when using the syntax "raise ... from ...", '
         "where the exception context is not an exception, "
@@ -113,7 +113,7 @@ def _is_raising(body: typing.List) -> bool:
     "E0711": (
         "NotImplemented raised - should raise NotImplementedError",
         "notimplemented-raised",
-        "Used when NotImplemented is raised instead of " "NotImplementedError",
+        "Used when NotImplemented is raised instead of NotImplementedError",
     ),
     "E0712": (
         "Catching an exception which doesn't inherit from Exception: %s",
@@ -124,7 +124,7 @@ def _is_raising(body: typing.List) -> bool:
     "W0702": (
         "No exception type(s) specified",
         "bare-except",
-        "Used when an except clause doesn't specify exceptions type to " "catch.",
+        "Used when an except clause doesn't specify exceptions type to catch.",
     ),
     "W0703": (
         "Catching too general exception %s",

diff --git a/pylint/checkers/format.py b/pylint/checkers/format.py
@@ -138,7 +138,7 @@
     "C0303": (
         "Trailing whitespace",
         "trailing-whitespace",
-        "Used when there is whitespace between the end of a line and the " "newline.",
+        "Used when there is whitespace between the end of a line and the newline.",
     ),
     "C0304": (
         "Final newline missing",

diff --git a/pylint/checkers/imports.py b/pylint/checkers/imports.py
@@ -211,7 +211,7 @@ def _make_graph(filename, dep_info, sect, gtype):
     "R0401": (
         "Cyclic import (%s)",
         "cyclic-import",
-        "Used when a cyclic import between two or more modules is " "detected.",
+        "Used when a cyclic import between two or more modules is detected.",
     ),
     "W0401": (
         "Wildcard import %s",
@@ -226,7 +226,7 @@ def _make_graph(filename, dep_info, sect, gtype):
     "W0403": (
         "Relative import %r, should be %r",
         "relative-import",
-        "Used when an import relative to the package directory is " "detected.",
+        "Used when an import relative to the package directory is detected.",
         {"maxversion": (3, 0)},
     ),
     "W0404": (
@@ -248,7 +248,7 @@ def _make_graph(filename, dep_info, sect, gtype):
     "C0410": (
         "Multiple imports on one line (%s)",
         "multiple-imports",
-        "Used when import statement importing multiple modules is " "detected.",
+        "Used when import statement importing multiple modules is detected.",
     ),
     "C0411": (
         "%s should be placed before %s",
@@ -262,7 +262,7 @@ def _make_graph(filename, dep_info, sect, gtype):
         "Used when imports are not grouped by packages",
     ),
     "C0413": (
-        'Import "%s" should be placed at the top of the ' "module",
+        'Import "%s" should be placed at the top of the module',
         "wrong-import-position",
         "Used when code and imports are mixed",
     ),

diff --git a/pylint/checkers/misc.py b/pylint/checkers/misc.py
@@ -80,7 +80,7 @@ class EncodingChecker(BaseChecker):
             "Used when a warning note as FIXME or XXX is detected.",
         ),
         "W0512": (
-            'Cannot decode using encoding "%s",' " unexpected byte at position %d",
+            'Cannot decode using encoding "%s", unexpected byte at position %d',
             "invalid-encoded-data",
             "Used when a source line cannot be decoded using the specified "
             "source file encoding.",

diff --git a/pylint/checkers/newstyle.py b/pylint/checkers/newstyle.py
@@ -31,7 +31,7 @@
     "E1004": (
         "Missing argument to super()",
         "missing-super-argument",
-        "Used when the super builtin didn't receive an " "argument.",
+        "Used when the super builtin didn't receive an argument.",
         {"maxversion": (3, 0)},
     ),
 }

diff --git a/pylint/checkers/python3.py b/pylint/checkers/python3.py
@@ -179,15 +179,15 @@ class Python3Checker(checkers.BaseChecker):
             "(Python 3 doesn't allow it)",
         ),
         "E1603": (
-            "Implicit unpacking of exceptions is not supported " "in Python 3",
+            "Implicit unpacking of exceptions is not supported in Python 3",
             "unpacking-in-except",
             "Python3 will not allow implicit unpacking of "
             "exceptions in except clauses. "
             "See http://www.python.org/dev/peps/pep-3110/",
             {"old_names": [("W0712", "unpacking-in-except")]},
         ),
         "E1604": (
-            "Use raise ErrorClass(args) instead of " "raise ErrorClass, args.",
+            "Use raise ErrorClass(args) instead of raise ErrorClass, args.",
             "old-raise-syntax",
             "Used when the alternate raise syntax "
             "'raise foo, bar' is used "
@@ -378,7 +378,7 @@ class Python3Checker(checkers.BaseChecker):
         "W1628": (
             "__hex__ method defined",
             "hex-method",
-            "Used when a __hex__ method is defined " "(method is not used by Python 3)",
+            "Used when a __hex__ method is defined (method is not used by Python 3)",
         ),
         "W1629": (
             "__nonzero__ method defined",
@@ -389,7 +389,7 @@ class Python3Checker(checkers.BaseChecker):
         "W1630": (
             "__cmp__ method defined",
             "cmp-method",
-            "Used when a __cmp__ method is defined " "(method is not used by Python 3)",
+            "Used when a __cmp__ method is defined (method is not used by Python 3)",
         ),
         # 'W1631': replaced by W1636
         "W1632": (
@@ -413,7 +413,7 @@ class Python3Checker(checkers.BaseChecker):
         "W1635": (
             "unichr built-in referenced",
             "unichr-builtin",
-            "Used when the unichr built-in is referenced " "(Use chr in Python 3)",
+            "Used when the unichr built-in is referenced (Use chr in Python 3)",
         ),
         "W1636": (
             "map built-in referenced when not iterating",

diff --git a/pylint/checkers/refactoring.py b/pylint/checkers/refactoring.py
@@ -96,7 +96,7 @@ class RefactoringChecker(checkers.BaseTokenChecker):
         "R1703": (
             "The if statement can be replaced with %s",
             "simplifiable-if-statement",
-            "Used when an if statement can be replaced with " "'bool(test)'. ",
+            "Used when an if statement can be replaced with 'bool(test)'. ",
             {"old_names": [("R0102", "simplifiable-if-statement")]},
         ),
         "R1704": (
@@ -203,7 +203,7 @@ class RefactoringChecker(checkers.BaseTokenChecker):
         "R1719": (
             "The if expression can be replaced with %s",
             "simplifiable-if-expression",
-            "Used when an if expression can be replaced with " "'bool(test)'. ",
+            "Used when an if expression can be replaced with 'bool(test)'. ",
         ),
     }
     options = (
@@ -213,7 +213,7 @@ class RefactoringChecker(checkers.BaseTokenChecker):
                 "default": 5,
                 "type": "int",
                 "metavar": "<int>",
-                "help": "Maximum number of nested blocks for function / " "method body",
+                "help": "Maximum number of nested blocks for function / method body",
             },
         ),
         (
@@ -1155,7 +1155,7 @@ class NotChecker(checkers.BaseChecker):
         "C0113": (
             'Consider changing "%s" to "%s"',
             "unneeded-not",
-            "Used when a boolean expression contains an unneeded " "negation.",
+            "Used when a boolean expression contains an unneeded negation.",
         )
     }
     name = "basic"

diff --git a/pylint/checkers/stdlib.py b/pylint/checkers/stdlib.py
@@ -97,7 +97,7 @@ class StdlibChecker(BaseChecker):
             {"maxversion": (3, 5)},
         ),
         "W1503": (
-            "Redundant use of %s with constant " "value %r",
+            "Redundant use of %s with constant value %r",
             "redundant-unittest-assert",
             "The first argument of assertTrue and assertFalse is "
             "a condition. If a constant is passed as parameter, that "
@@ -119,7 +119,7 @@ class StdlibChecker(BaseChecker):
             "By default, the first parameter is the group param, not the target param. ",
         ),
         "W1507": (
-            "Using copy.copy(os.environ). Use os.environ.copy() " "instead. ",
+            "Using copy.copy(os.environ). Use os.environ.copy() instead. ",
             "shallow-copy-environ",
             "os.environ is not a dict object but proxy object, so "
             "shallow copy has still effects on original object. "
Original file line number	Diff line number	Diff line change
Expand Up		@@ -243,3 +243,5 @@ contributors:
		* Scott Worley: contributor

		* Michael Hudson-Doyle

		* Lucas Cimon: contributor