Closes #956, closes #854

setup.cfg

@@ -35,6 +35,7 @@ exclude =
   .eggs
   *.egg
   # These folders contain code badly written for reasons:
+  # Project spefic, do not copy.
   tests/fixtures/**
   tests/**/snapshots/**
 

tests/fixtures/noqa.py

@@ -620,3 +620,8 @@ def consecutive_yields():
     print(some_sized[len(some_sized) - 2])  # noqa: WPS530
 
 deep_func(a)(b)(c)(d)  # noqa: WPS233
+
+extra_new_line = [  # noqa: WPS355
+
+    'wrong',
+]

tests/test_checker/test_noqa.py

@@ -133,6 +133,7 @@
     'WPS352': 1,
     'WPS353': 1,
     'WPS354': 1,
+    'WPS355': 1,
 
     'WPS400': 0,
     'WPS401': 0,

tests/test_visitors/test_tokenize/test_statements/test_bracket_empty_line.py

@@ -0,0 +1,180 @@
+# -*- coding: utf-8 -*-
+
+import pytest
+
+from wemake_python_styleguide.violations.consistency import (
+    BracketBlankLineViolation,
+)
+from wemake_python_styleguide.visitors.tokenize.statements import (
+    BracketLocationVisitor,
+)
+
+# Correct:
+
+correct_empty_module = ''
+correct_single_line = 'arr = []'
+correct_single_line_items = 'arr = [1, 2, 3]'
+correct_single_line_call = 'some(1, 2, 3)'
+
+correct_method = """
+class Some(object):
+    '''
+    Dco.
+
+    Some [
+        Example,
+    ]
+    '''
+
+    def __init__(self, node=None, text: Optional[str] = None) -> None:
+        ...
+"""
+
+correct_blank_line_in_middle_list = """
+arr = [
+    1,
+
+    2,
+]
+"""
+
+correct_blank_line_in_middle_dict = """
+arr = {
+    1:
+
+    2,
+}
+"""
+
+correct_blank_line_in_middle_parens = """
+arr = (
+    1,
+
+    2,
+)
+"""
+
+correct_comment_start_of_list = """
+arr = [
+    # comment
+    1,
+
+    2,
+]
+"""
+
+correct_comment_in_middle_of_list = """
+arr = [
+    1,
+
+    # comment
+    2,
+]
+"""
+
+# Wrong:
+
+wrong_blank_line_at_start_list = """
+some = [
+
+    1,
+    2,
+    3,
+]
+"""
+
+wrong_blank_line_at_end_list = """
+some = [
+    1,
+    2,
+    3,
+
+]
+"""
+
+wrong_blank_line_after_comment = """
+extra_new_line = [  # some
+
+    'wrong',
+]
+"""
+
+wrong_blank_line_at_start_dict = """
+arr = {
+
+    1: 2,
+}
+"""
+
+wrong_blank_line_at_end_dict = """
+arr = {
+    1: 2,
+
+}
+"""
+
+wrong_blank_line_at_start_parens = """
+arr = (
+
+    1,
+    2,
+)
+"""
+
+wrong_blank_line_at_end_parens = """
+arr = (
+    1, 2,
+
+)
+"""
+
+
+@pytest.mark.parametrize('code', [
+    correct_empty_module,
+    correct_single_line,
+    correct_single_line_call,
+    correct_single_line_items,
+    correct_method,
+    correct_blank_line_in_middle_list,
+    correct_blank_line_in_middle_dict,
+    correct_blank_line_in_middle_parens,
+    correct_comment_start_of_list,
+    correct_comment_in_middle_of_list,
+])
+def test_correct_blank_lines(
+    parse_tokens,
+    assert_errors,
+    default_options,
+    code,
+):
+    """Ensures that correct blank lines work."""
+    file_tokens = parse_tokens(code)
+
+    visitor = BracketLocationVisitor(default_options, file_tokens=file_tokens)
+    visitor.run()
+
+    assert_errors(visitor, [])
+
+
+@pytest.mark.parametrize('code', [
+    wrong_blank_line_at_start_list,
+    wrong_blank_line_at_end_list,
+    wrong_blank_line_after_comment,
+    wrong_blank_line_at_start_dict,
+    wrong_blank_line_at_end_dict,
+    wrong_blank_line_at_start_parens,
+    wrong_blank_line_at_end_parens,
+])
+def test_wrong_blank_lines(
+    parse_tokens,
+    assert_errors,
+    default_options,
+    code,
+):
+    """Ensures that incorrect blank lines raise a warning."""
+    file_tokens = parse_tokens(code)
+
+    visitor = BracketLocationVisitor(default_options, file_tokens=file_tokens)
+    visitor.run()
+
+    assert_errors(visitor, [BracketBlankLineViolation])

wemake_python_styleguide/logic/tokens.py

@@ -1,7 +1,24 @@
 # -*- coding: utf-8 -*-
 
 import tokenize
-from typing import Container, Iterable, Tuple
+import types
+from typing import Container, FrozenSet, Iterable, List, Mapping, Tuple
+
+MATCHING: Mapping[int, int] = types.MappingProxyType({
+    tokenize.LBRACE: tokenize.RBRACE,
+    tokenize.LSQB: tokenize.RSQB,
+    tokenize.LPAR: tokenize.RPAR,
+})
+
+NEWLINES: FrozenSet[int] = frozenset((
+    tokenize.NL,
+    tokenize.NEWLINE,
+))
+
+ALLOWED_EMPTY_LINE_TOKENS: FrozenSet[int] = frozenset((
+    *NEWLINES,
+    *MATCHING.values(),
+))
 
 
 def split_prefixes(token: tokenize.TokenInfo) -> Tuple[str, str]:
@@ -44,3 +61,26 @@ def only_contains(
 def get_comment_text(token: tokenize.TokenInfo) -> str:
     """Returns comment without `#` char from comment tokens."""
     return token.string[1:].strip()
+
+
+def get_reverse_bracket(bracket: tokenize.TokenInfo) -> int:
+    """
+    Returns the reverse closing bracket for an openning token.
+
+    >>> import tokenize
+    >>> import token
+    >>> bracket = tokenize.TokenInfo(token.RPAR, ")", 6, 7, "(a, b)")
+    >>> get_reverse_bracket(bracket) == token.LPAR
+    True
+
+    """
+    index = list(MATCHING.values()).index(bracket.exact_type)
+    return list(MATCHING.keys())[index]
+
+
+def last_bracket(tokens: List[tokenize.TokenInfo], index: int) -> bool:
+    """Tells whether the given index is the last bracket token in line."""
+    return only_contains(
+        tokens[index + 1:],
+        NEWLINES.union({tokenize.COMMENT}),
+    )

wemake_python_styleguide/violations/consistency.py

@@ -80,6 +80,7 @@
    MultilineLoopViolation
    IncorrectYieldFromTargetViolation
    ConsecutiveYieldsViolation
+   BracketBlankLineViolation
 
 Consistency checks
 ------------------
@@ -139,6 +140,7 @@
 .. autoclass:: MultilineLoopViolation
 .. autoclass:: IncorrectYieldFromTargetViolation
 .. autoclass:: ConsecutiveYieldsViolation
+.. autoclass:: BracketBlankLineViolation
 
 """
 
@@ -2012,3 +2014,36 @@ class ConsecutiveYieldsViolation(ASTViolation):
 
     error_template = 'Found consecutive `yield` expressions'
     code = 354
+
+
+@final
+class BracketBlankLineViolation(TokenizeViolation):
+    """
+    Forbids useless blank lines before and after brackets.
+
+    Reasoning:
+        We do this for consistency.
+
+    Solution:
+        Remove blank lines from the start and from the end of a collection.
+
+    Example::
+
+        # Correct:
+        arr = [
+            1,
+            2
+        ]
+
+        # Wrong:
+        arr = [
+            1,
+            2
+        ]
+
+    .. versionadded:: 0.13.0
+
+    """
+
+    error_template = 'Found an unnecessary blank line before a bracket'
+    code = 355