Added a check to raise error on missing whitespace around arithmetic …

CONTRIBUTORS.txt

@@ -110,3 +110,5 @@ Order doesn't matter (not that much, at least ;)
 * Alexander Todorov: added new errro conditions to 'bad-super-call'.
 
 * Roy Williams (Lyft): added check for implementing __eq__ without implementing __hash__.
+
+* Aswin Murugesh: Added checks for spaces around arithmetic operators

ChangeLog

@@ -183,6 +183,9 @@ Release date: tba
     * Added a new Python 3 warning around implementing '__div__' or '__idiv__'
       as those methods are phased out in Python 3.
 
+    * Added check for whitespace around arithmetic operators
+
+      Closes #1110
 
 What's new in Pylint 1.6.3?
 ===========================

pylint/checkers/format.py

@@ -660,6 +660,8 @@ def _name_construct(token):
                 return 'bracket'
             elif token[1] in ('<', '>', '<=', '>=', '!=', '=='):
                 return 'comparison'
+            elif token[1] in ['+', '-', '/', '*', '**']:
+                return 'arithmetic operator'
             else:
                 if self._inside_brackets('('):
                     return 'keyword argument assignment'
@@ -695,6 +697,25 @@ def _name_construct(token):
                              args=(count, state, position, construct,
                                    _underline_token(token)))
 
+    def _check_arithmetic_operators(self, tokens, i):
+        "Check that the arithmetic operators are surrounded by spaces wherever appropriate"
+        if tokens[i][1] in ['+', '-']:
+            if tokens[i-1][1] not in [tokenize.NUMBER, tokenize.NAME]:
+                self._check_space(tokens, i, (_MUST, _MUST_NOT))
+            else:
+                self._check_space(tokens, i, (_MUST, _MUST))
+        elif tokens[i][1] in ['*', '**']:
+            if tokens[i-1][1] in ['('] or tokens[i-1][0] == tokenize.NL:
+                self._check_space(tokens, i, (_MUST_NOT, _MUST_NOT))
+            elif tokens[i-1][1] in [',', 'lambda']:
+                self._check_space(tokens, i, (_MUST, _MUST_NOT))
+            else:
+                self._check_space(tokens, i, (_MUST, _MUST))
+        else:
+            self._check_space(tokens, i, (_MUST, _MUST))
+
+
+
     def _inside_brackets(self, left):
         return self._bracket_stack[-1] == left
 
@@ -717,6 +738,8 @@ def _prepare_token_dispatcher(self):
 
             (['lambda'], self._open_lambda),
 
+            (['*', '+', '-', '*', '/', '**'], self._check_arithmetic_operators),
+
             ]
 
         dispatch = {}

pylint/test/functional/arithmetic_operators.py

@@ -0,0 +1,8 @@
+# pylint: disable=missing-docstring,invalid-name,unused-argument
+def sample_function(*args, **kwargs):
+    pass
+
+a = 5*4  # [bad-whitespace]
+b = a* 20  # [bad-whitespace]
+b = 4 /20  # [bad-whitespace]
+c = 4 + 30

pylint/test/functional/arithmetic_operators.txt

@@ -0,0 +1,9 @@
+bad-whitespace:5::"Exactly one space required around arithmetic operator
+a = 5*4  # [bad-whitespace]
+     ^"
+bad-whitespace:6::"Exactly one space required before arithmetic operator
+b = a* 20  # [bad-whitespace]
+     ^"
+bad-whitespace:7::"Exactly one space required after arithmetic operator
+b = 4 /20  # [bad-whitespace]
+      ^"

pylint/test/functional/bad_continuation.py

@@ -59,8 +59,8 @@
             'long continuation',
     'key2': 'breaking'
         'wrong',  # [bad-continuation]
-    'key3': 2*(
-        2+2),
+    'key3': 2 * (
+        2 + 2),
     'key4': ('parenthesis',
              'continuation')  # No comma here
     }

pylint/test/functional/cellvar_escaping_loop.py

@@ -97,7 +97,7 @@ def bad_case4():
     for i in range(10):
         def nested():
             """Nested function."""
-            return i**2  # [cell-var-from-loop]
+            return i ** 2  # [cell-var-from-loop]
         lst.append(nested)
     return lst
 

pylint/test/functional/deprecated_lambda.py

@@ -3,7 +3,7 @@
 import functools
 
 # Don't do this, use a comprehension instead.
-assert map(lambda x: x*2, [1, 2, 3]) == [2, 4, 6] # [deprecated-lambda]
+assert map(lambda x: x * 2, [1, 2, 3]) == [2, 4, 6] # [deprecated-lambda]
 
 assert filter(lambda x: x != 1, [1, 2, 3]) == [2, 3] # [deprecated-lambda]
 

pylint/test/functional/genexp_in_class_scope.py

@@ -3,4 +3,4 @@
 
 class MyClass(object):
     var1 = []
-    var2 = list(value*2 for value in var1)
+    var2 = list(value * 2 for value in var1)

pylint/test/functional/lost_exception.py

@@ -5,7 +5,7 @@ def insidious_break_and_return():
         my_var = 0
 
         try:
-            my_var += 1.0/i
+            my_var += 1.0 / i
             if i < -3:
                 break
             else:
@@ -24,7 +24,7 @@ def break_and_return():
         if i:
             break
         try:
-            my_var += 1.0/i
+            my_var += 1.0 / i
         finally:
             for _ in range(2):
                 if True:

pylint/test/functional/misplaced_bare_raise.py

@@ -61,7 +61,7 @@ class A(object):
 # not to rely on it.
 exc = None
 try:
-    1/0
+    1 / 0
 except ZeroDivisionError as exc:
     pass
 if exc:

pylint/test/input/func_bad_cont_dictcomp_py27.py

@@ -11,15 +11,15 @@
       range(3)}
 
 # Dictionary comprehensions with multiple loops broken in different places
-C3 = {x*y: (x, y) for x in range(3) for y in range(3)}
+C3 = {x * y: (x, y) for x in range(3) for y in range(3)}
 
-C4 = {x*y: (x, y)
+C4 = {x * y: (x, y)
       for x in range(3) for y in range(3)}
 
-C5 = {x*y: (x, y) for x
+C5 = {x * y: (x, y) for x
       in range(3) for y in range(3)}
 
-C6 = {x*y: (x, y) for x in range(3)
+C6 = {x * y: (x, y) for x in range(3)
       for y in range(3)}
 
 C7 = {key:

pylint/test/input/func_w0613.py

@@ -25,8 +25,8 @@ def selected(cls, *args, **kwargs):
 
     def using_inner_function(self, etype, size=1):
         """return a fake result set for a particular entity type"""
-        rset = AAAA([('A',)]*size, '%s X' % etype,
-                    description=[(etype,)]*size)
+        rset = AAAA([('A',)] * size, '%s X' % etype,
+                    description=[(etype,)] * size)
         def inner(row, col=0, etype=etype, req=self, rset=rset):
             """inner using all its argument"""
             # pylint: disable = E1103