Issue 5870 - Implement the new ElemHideEmulation filter type

compiled/filter/Filter.cpp

 /*
  * 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 97 matching lines @@
   } data;
   bool needConversion = false;
   DependentString error;
 
   Filter::Type type = CommentFilter::Parse(text);
   if (type == Filter::Type::UNKNOWN)
     type = ElemHideBase::Parse(text, data.elemhide, needConversion);
   if (type == Filter::Type::UNKNOWN)
     type = RegExpFilter::Parse(text, error, data.regexp);
 
-  if (needConversion && (type == ElemHideException::classType || type == ElemHideEmulationFilter::classType))

[sergei, 2018/02/12 12:53:20]

Firstly I thought about moving of `(type == ElemHideException::classType || type
== ElemHideEmulationFilter::classType)` inside `ElemHideBase::Parse`, it seems a
detail of ElemHide classes, here we just check the value of needConversion and
do the conversion if there is a necessity in it. However it seems it's redundant
at all. If needConversion is set to true then the type can be either
ELEMHIDEEXCEPTION if `exception` variable in ElemHideBase::Parse is true or
ELEMHIDEEMULATION if that `exception` variable is false, therefore if
needConversion is true then `(type == ElemHideException::classType || type ==
ElemHideEmulationFilter::classType)` is always true.
I think it can be just removed.

[hub, 2018/02/12 18:14:40]

I was being overly paranoid.

Done.

+  if (needConversion)
     text = ElemHideBase::ConvertFilter(text, data.elemhide.mSelectorStart);
 
   // At that point we failed the conversion.
   if (text.empty())
     return nullptr;
 
   auto knownFilter = knownFilters.find(text);
   if (knownFilter)
   {
     knownFilter->second->AddRef();
@@ skipping 36 matching lines @@
     knownFilters[filter->mText] = filter.get();
   else
     // This is a hack: we looked up the entry using text but create it using
     // filter->mText. This works because both are equal at this point. However,
     // text refers to a temporary buffer which will go away.
     knownFilter.assign(filter->mText, filter.get());
   exit_context();
 
   return filter.release();
 }