linter: Extend no-space-before-bracket linting rule.

docs/code-style.md

@@ -242,8 +242,6 @@ code a lot uglier, in which case it's fine to go up to 120 or so.
 
 Whitespace guidelines:
 
--   Put one space between keywords like `if` and `while` and their
-    associated open paren.
 -   Put no space before or after the open paren for function calls and
     no space before the close paren for function calls.
 

tools/linter_lib/custom_check.py

@@ -249,8 +249,10 @@ def build_custom_checkers(by_lang):
          'description': 'Missing : after type in type annotation'},
         {'pattern': "#type",
          'description': 'Missing whitespace after "#" in type annotation'},
-        {'pattern': 'if[(]',
-         'description': 'Missing space between if and ('},
+        {'pattern': r'\b(if|else|while)[(]',
+         'description': 'Put a space between statements like if, else, etc. and (.',
+         'good_lines': ['if (1 == 2):', 'while (foo == bar):'],
+         'bad_lines': ['if(1 == 2):', 'while(foo == bar):']},
         {'pattern': ", [)]",
          'description': 'Unnecessary whitespace between "," and ")"'},
         {'pattern': "%  [(]",