Noissue - Remove redundant assignment to zero

lib/filterClasses.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 714 matching lines @@
 RegExpFilter.fromText = function(text)
 {
   let blocking = true;
   let origText = text;
   if (text.indexOf("@@") == 0)
   {
     blocking = false;
     text = text.substr(2);
   }
 
   let contentType = null;

[kzar, 2018/06/07 13:34:55]

It's kinda confusing to reason about, but I wonder if we could just assign 0
here and remove the other == null check as well?

In other words could contentType ever be 0 at the point we're checking it's not
null?

[Manish Jethani, 2018/06/07 14:23:31]

In theory one could write a filter that specifically disables the filter on
every single content type, thus yielding the value 0 in the end. It helps to
have null as a special value to indicate that no content type was specified, at
which point the filter object can default to the value in the prototype object.

So yeah I think we need the null.

[kzar, 2018/06/07 14:32:32]

Yea, I guess you're right. It seems kind of unlikely that a filter explicitly
disables every single content type once, then one again... but if it did I guess
the result would be `RegExpFilter.prototype.contentType & ~contentType` instead
of `0 & ~contentType` without the null.

[Manish Jethani, 2018/06/07 14:38:22]

If every single type is excluded the final value of contentType would be 0, also
the initial value. Then the RegExpFilter constructor would have the following
check:

  if (contentType != 0)
    this.contentType = contentType;

So for 0 it would result in applying the filter to all content types - the
opposite of what the filter author intended. With null we avoid this.

   let matchCase = null;
   let domains = null;
   let sitekeys = null;
   let thirdParty = null;
   let collapse = null;
   let csp = null;
   let rewrite = null;
   let options;
   let match = (text.indexOf("$") >= 0 ? Filter.optionsRegExp.exec(text) : null);
   if (match)
   {
     options = match[1].split(",");
     text = match.input.substr(0, match.index);
     for (let option of options)
     {
       let value = null;
       let separatorIndex = option.indexOf("=");
       if (separatorIndex >= 0)
       {
         value = option.substr(separatorIndex + 1);
         option = option.substr(0, separatorIndex);
       }
       option = option.replace(/-/, "_").toUpperCase();
       if (option in RegExpFilter.typeMap)
       {
-        if (contentType == null)
-          contentType = 0;
         contentType |= RegExpFilter.typeMap[option];
 
         if (option == "CSP" && value)
           csp = value;
       }
       else if (option[0] == "~" && option.substr(1) in RegExpFilter.typeMap)
       {
         if (contentType == null)
           ({contentType} = RegExpFilter.prototype);
         contentType &= ~RegExpFilter.typeMap[option.substr(1)];
@@ skipping 309 matching lines @@
  */
 function ElemHideEmulationFilter(text, domains, selector)
 {
   ElemHideBase.call(this, text, domains, selector);
 }
 exports.ElemHideEmulationFilter = ElemHideEmulationFilter;
 
 ElemHideEmulationFilter.prototype = extend(ElemHideBase, {
   type: "elemhideemulation"
 });