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')`.

22 files changed, 186 insertions, 52 deletions

diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
index eea7b2c6d..5d08fd307 100644
--- 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
index 396030a8f..962141f2f 100644
--- 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
index e001dd3d4..8812fc20c 100644
--- 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
index 52be3c3f8..4a08f9325 100644
--- 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
index c386d70e6..b0a85906b 100644
--- a/pylint/checkers/classes.py
+++ b/pylint/checkers/classes.py
@@ -459,12 +459,12 @@ MSGS = {
     "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 @@ MSGS = {
     "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 @@ MSGS = {
         "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 @@ MSGS = {
     "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 @@ MSGS = {
     "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
index 0c1a21cb9..a0c48b978 100644
--- a/pylint/checkers/design_analysis.py
+++ b/pylint/checkers/design_analysis.py
@@ -86,7 +86,7 @@ MSGS = {
     "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
index 4eb65d923..e0a449ca8 100644
--- a/pylint/checkers/exceptions.py
+++ b/pylint/checkers/exceptions.py
@@ -88,7 +88,7 @@ MSGS = {
         "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 @@ MSGS = {
     "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 @@ MSGS = {
     "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
index 9e353e6d5..b5f35cd00 100644
--- a/pylint/checkers/format.py
+++ b/pylint/checkers/format.py
@@ -138,7 +138,7 @@ MSGS = {
     "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
index 77ff79a60..e2d00eb76 100644
--- a/pylint/checkers/imports.py
+++ b/pylint/checkers/imports.py
@@ -211,7 +211,7 @@ MSGS = {
     "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 @@ MSGS = {
     "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 @@ MSGS = {
     "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 @@ MSGS = {
         "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
index 767da45ab..b0f52ca8b 100644
--- 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
index 0da6a5228..89d31653b 100644
--- a/pylint/checkers/newstyle.py
+++ b/pylint/checkers/newstyle.py
@@ -31,7 +31,7 @@ MSGS = {
     "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
index 34be179f0..44ebf2991 100644
--- a/pylint/checkers/python3.py
+++ b/pylint/checkers/python3.py
@@ -179,7 +179,7 @@ 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. "
@@ -187,7 +187,7 @@ class Python3Checker(checkers.BaseChecker):
             {"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
index e8f35ca5c..47a702587 100644
--- 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
index 57692b93d..7dad31d28 100644
--- 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. "
diff --git a/pylint/checkers/strings.py b/pylint/checkers/strings.py
index 0f7123a71..d1f227133 100644
--- a/pylint/checkers/strings.py
+++ b/pylint/checkers/strings.py
@@ -30,11 +30,13 @@ from collections import Counter
 
 import astroid
 from astroid.arguments import CallSite
+from astroid.node_classes import Const
 from pylint.interfaces import ITokenChecker, IAstroidChecker, IRawChecker
 from pylint.checkers import BaseChecker, BaseTokenChecker
 from pylint.checkers import utils
 from pylint.checkers.utils import check_messages
 
+_AST_NODE_STR_TYPES = ("__builtin__.unicode", "__builtin__.str", "builtins.str")
 
 _PY3K = sys.version_info[:2] >= (3, 0)
 _PY27 = sys.version_info[:2] == (2, 7)
@@ -43,7 +45,7 @@ MSGS = {
     "E1300": (
         "Unsupported format character %r (%#02x) at index %d",
         "bad-format-character",
-        "Used when an unsupported format character is used in a format" "string.",
+        "Used when an unsupported format character is used in a format string.",
     ),
     "E1301": (
         "Format string ends in middle of conversion specifier",
@@ -106,7 +108,7 @@ MSGS = {
     "E1310": (
         "Suspicious argument in %s.%s call",
         "bad-str-strip-call",
-        "The argument to a str.{l,r,}strip call contains a" " duplicate character, ",
+        "The argument to a str.{l,r,}strip call contains a duplicate character, ",
     ),
     "W1302": (
         "Invalid format string",
@@ -546,14 +548,14 @@ class StringFormatChecker(BaseChecker):
 class StringConstantChecker(BaseTokenChecker):
     """Check string literals"""
 
-    __implements__ = (ITokenChecker, IRawChecker)
+    __implements__ = (IAstroidChecker, ITokenChecker, IRawChecker)
     name = "string_constant"
     msgs = {
         "W1401": (
             "Anomalous backslash in string: '%s'. "
             "String constant might be missing an r prefix.",
             "anomalous-backslash-in-string",
-            "Used when a backslash is in a literal string but not as an " "escape.",
+            "Used when a backslash is in a literal string but not as an escape.",
         ),
         "W1402": (
             "Anomalous Unicode escape in byte string: '%s'. "
@@ -562,6 +564,13 @@ class StringConstantChecker(BaseTokenChecker):
             "Used when an escape like \\u is encountered in a byte "
             "string where it has no effect.",
         ),
+        "W1403": (
+            "Implicit string concatenation found in %s",
+            "implicit-str-concat-in-sequence",
+            "String literals are implicitly concatenated in a "
+            "literal iterable definition : "
+            "maybe a comma is missing ?",
+        ),
     }
 
     # Characters that have a special meaning after a backslash in either
@@ -575,15 +584,55 @@ class StringConstantChecker(BaseTokenChecker):
     # Unicode strings.
     UNICODE_ESCAPE_CHARACTERS = "uUN"
 
+    def __init__(self, *args, **kwargs):
+        super(StringConstantChecker, self).__init__(*args, **kwargs)
+        self.string_tokens = {}  # token position -> (token value, next token)
+
     def process_module(self, module):
         self._unicode_literals = "unicode_literals" in module.future_imports
 
     def process_tokens(self, tokens):
-        for (tok_type, token, (start_row, _), _, _) in tokens:
+        for i, (tok_type, token, start, _, _) in enumerate(tokens):
             if tok_type == tokenize.STRING:
                 # 'token' is the whole un-parsed token; we can look at the start
                 # of it to see whether it's a raw or unicode string etc.
-                self.process_string_token(token, start_row)
+                self.process_string_token(token, start[0])
+                next_token = tokens[i + 1] if i + 1 < len(tokens) else None
+                self.string_tokens[start] = (str_eval(token), next_token)
+
+    @check_messages(*(MSGS.keys()))
+    def visit_list(self, node):
+        self.check_for_concatenated_strings(node, "list")
+
+    @check_messages(*(MSGS.keys()))
+    def visit_set(self, node):
+        self.check_for_concatenated_strings(node, "set")
+
+    @check_messages(*(MSGS.keys()))
+    def visit_tuple(self, node):
+        self.check_for_concatenated_strings(node, "tuple")
+
+    def check_for_concatenated_strings(self, iterable_node, iterable_type):
+        for elt in iterable_node.elts:
+            if isinstance(elt, Const) and elt.pytype() in _AST_NODE_STR_TYPES:
+                if elt.col_offset < 0:
+                    # This can happen in case of escaped newlines
+                    continue
+                matching_token, next_token = self.string_tokens[
+                    (elt.lineno, elt.col_offset)
+                ]
+                if matching_token != elt.value and next_token is not None:
+                    next_token_type, next_token_pos = next_token[0], next_token[2]
+                    # We do not warn if string concatenation happens over a newline
+                    if (
+                        next_token_type == tokenize.STRING
+                        and next_token_pos[0] == elt.lineno
+                    ):
+                        self.add_message(
+                            "implicit-str-concat-in-sequence",
+                            line=elt.lineno,
+                            args=(iterable_type,),
+                        )
 
     def process_string_token(self, token, start_row):
         quote_char = None
@@ -660,3 +709,19 @@ def register(linter):
     """required method to auto register this checker """
     linter.register_checker(StringFormatChecker(linter))
     linter.register_checker(StringConstantChecker(linter))
+
+
+def str_eval(token):
+    """
+    Mostly replicate `ast.literal_eval(token)` manually to avoid any performance hit.
+    This supports f-strings, contrary to `ast.literal_eval`.
+    We have to support all string literal notations:
+    https://docs.python.org/3/reference/lexical_analysis.html#string-and-bytes-literals
+    """
+    if token[0:2].lower() in ("fr", "rf"):
+        token = token[2:]
+    elif token[0].lower() in ("r", "u", "f"):
+        token = token[1:]
+    if token[0:3] in ('"""', "'''"):
+        return token[3:-3]
+    return token[1:-1]
diff --git a/pylint/checkers/typecheck.py b/pylint/checkers/typecheck.py
index 5df5c9504..901161817 100644
--- a/pylint/checkers/typecheck.py
+++ b/pylint/checkers/typecheck.py
@@ -253,7 +253,7 @@ MSGS = {
     "E1121": (
         "Too many positional arguments for %s call",
         "too-many-function-args",
-        "Used when a function call passes too many positional " "arguments.",
+        "Used when a function call passes too many positional arguments.",
     ),
     "E1123": (
         "Unexpected keyword argument %r in %s call",
diff --git a/pylint/checkers/variables.py b/pylint/checkers/variables.py
index bf6825644..78d78a913 100644
--- a/pylint/checkers/variables.py
+++ b/pylint/checkers/variables.py
@@ -286,7 +286,7 @@ MSGS = {
     "E0601": (
         "Using variable %r before assignment",
         "used-before-assignment",
-        "Used when a local variable is accessed before it's " "assignment.",
+        "Used when a local variable is accessed before it's assignment.",
     ),
     "E0602": (
         "Undefined variable %r",
@@ -357,7 +357,7 @@ MSGS = {
     "W0621": (
         "Redefining name %r from outer scope (line %s)",
         "redefined-outer-name",
-        "Used when a variable's name hides a name defined in the outer " "scope.",
+        "Used when a variable's name hides a name defined in the outer scope.",
     ),
     "W0622": (
         "Redefining built-in %r",
@@ -367,7 +367,7 @@ MSGS = {
     "W0623": (
         "Redefining name %r from %s in exception handler",
         "redefine-in-handler",
-        "Used when an exception handler assigns the exception " "to an existing name",
+        "Used when an exception handler assigns the exception to an existing name",
     ),
     "W0631": (
         "Using possibly undefined loop variable %r",
diff --git a/pylint/lint.py b/pylint/lint.py
index 7e5414540..6c11dfc2a 100644
--- a/pylint/lint.py
+++ b/pylint/lint.py
@@ -190,7 +190,7 @@ MSGS = {
     "I0011": (
         "Locally disabling %s (%s)",
         "locally-disabled",
-        "Used when an inline option disables a message or a messages " "category.",
+        "Used when an inline option disables a message or a messages category.",
     ),
     "I0013": (
         "Ignoring entire file",
diff --git a/pylint/test/functional/bad_continuation.py b/pylint/test/functional/bad_continuation.py
index b1c3479c8..1c73a1122 100644
--- a/pylint/test/functional/bad_continuation.py
+++ b/pylint/test/functional/bad_continuation.py
@@ -1,5 +1,5 @@
 """Regression test case for bad-continuation."""
-# pylint: disable=print-statement,using-constant-test,missing-docstring,wrong-import-position
+# pylint: disable=print-statement,implicit-str-concat-in-sequence,using-constant-test,missing-docstring,wrong-import-position
 # Various alignment for brackets
 from __future__ import print_function
 
diff --git a/pylint/test/functional/implicit_str_concat_in_sequence.py b/pylint/test/functional/implicit_str_concat_in_sequence.py
new file mode 100644
index 000000000..8c4b5cb46
--- /dev/null
+++ b/pylint/test/functional/implicit_str_concat_in_sequence.py
@@ -0,0 +1,26 @@
+#pylint: disable=bad-continuation,invalid-name,missing-docstring
+
+# Basic test with a list
+TEST_LIST1 = ['a' 'b']  # [implicit-str-concat-in-sequence]
+# Testing with unicode strings in a tuple, with a comma AFTER concatenation
+TEST_LIST2 = (u"a" u"b", u"c")  # [implicit-str-concat-in-sequence]
+# Testing with raw strings in a set, with a comma BEFORE concatenation
+TEST_LIST3 = {r'''a''', r'''b''' r'''c'''}  # [implicit-str-concat-in-sequence]
+# Testing that only ONE warning is generated when string concatenation happens
+# in the middle of a list
+TEST_LIST4 = ["""a""", """b""" """c""", """d"""]  # [implicit-str-concat-in-sequence]
+
+# The following shouldn't raise a warning because it is a function call
+print('a', 'bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb' 'ccc')
+
+# The following shouldn't raise a warning because string literals are
+# on different lines
+TEST_LIST5 = ('a', 'b'
+              'c')
+
+# The following shouldn't raise a warning because of the escaped newline
+TEST_LIST6 = ('a' 'bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb \
+              ccc')
+
+# No warning for bytes
+TEST_LIST7 = [b'A' b'B']
diff --git a/pylint/test/functional/implicit_str_concat_in_sequence.txt b/pylint/test/functional/implicit_str_concat_in_sequence.txt
new file mode 100644
index 000000000..b9e1cbba9
--- /dev/null
+++ b/pylint/test/functional/implicit_str_concat_in_sequence.txt
@@ -0,0 +1,4 @@
+implicit-str-concat-in-sequence:4::Implicit string concatenation found in list
+implicit-str-concat-in-sequence:6::Implicit string concatenation found in tuple
+implicit-str-concat-in-sequence:8::Implicit string concatenation found in set
+implicit-str-concat-in-sequence:11::Implicit string concatenation found in list
diff --git a/pylint/test/unittest_checker_strings.py b/pylint/test/unittest_checker_strings.py
index 57dc0af8d..4cac73747 100644
--- a/pylint/test/unittest_checker_strings.py
+++ b/pylint/test/unittest_checker_strings.py
@@ -10,6 +10,28 @@ from pylint.checkers import strings
 from pylint.testutils import CheckerTestCase, Message
 
 
+TEST_TOKENS = (
+    '"X"',
+    "'X'",
+    "'''X'''",
+    '"""X"""',
+    'r"X"',
+    "R'X'",
+    'u"X"',
+    "F'X'",
+    'f"X"',
+    "F'X'",
+    'fr"X"',
+    'Fr"X"',
+    'fR"X"',
+    'FR"X"',
+    'rf"X"',
+    'rF"X"',
+    'Rf"X"',
+    'RF"X"',
+)
+
+
 class TestStringChecker(CheckerTestCase):
     CHECKER_CLASS = strings.StringFormatChecker
 
@@ -58,3 +80,7 @@ class TestStringChecker(CheckerTestCase):
                 )
             ):
                 self.checker.visit_binop(node)
+
+    def test_str_eval(self):
+        for token in TEST_TOKENS:
+            assert strings.str_eval(token) == "X"