Issue 4394 - Create a filter class for element hiding emulation filters

chrome/content/elemHideEmulation.js

+var propertySelectorRegExp = /\[\-abp\-properties=(["'])([^"']+)\1\]/;
+
 function splitSelector(selector)
 {
   if (selector.indexOf(",") == -1)
     return [selector];
 
   var selectors = [];
   var start = 0;
   var level = 0;
   var sep = "";
 
@@ skipping 109 matching lines @@
   },
 
   load: function(callback)
   {
     this.getFiltersFunc(function(patterns)
     {
       this.patterns = [];
       for (var i = 0; i < patterns.length; i++)
       {
         var pattern = patterns[i];
-
-        // We currently don't support any element hiding emulation feature
-        // except for property selectors, so we remove rules that use other
-        // features. See https://issues.adblockplus.org/ticket/3143.
-        if (pattern.features != elemHideEmulationFeatureMap.PROPERTY_SELECTOR)

[kzar, 2016/11/04 15:45:56]

Before I suggested adding a supportedFeatures parameters to the
ElemHideEmulation constructor but I had another idea.

How about we turn the parameters into a single options Object, so things like
getFiltersFunc and addSelectorsFunc are properties on that? Since most features
will require some special functions to be passed in I suppose we can make them
all optional and then only enable features for which the functions have been
provided. ElemHideEmulation instances could then have a supportedFeatures
property which is assigned based on the functions provided to the constructor.

Then we could do something like `if (pattern.features &
~this.supportedFeatures)` to check if any unsupported features are required for
the filter.

[Felix Dahlke, 2016/11/04 16:43:35]

I'm not sure. For one, I feel that logic belongs in filterClasses: A filter is
an ElemHideEmulation filter if it has features that need to be emulated. A
filter is an ElemHide filter if its syntax is natively supported by the browser.
In that case we wouldn't even have to run this content script.

Secondly, while I tried to make sure we already have an idea for how we could
deal with features that are natively supported in some browsers but not all, for
now this is a completely theoretical discussion since -abp-properties is a bit
unlikely to be natively supported anywhere, and :has is not supported in any
browser, it's still just a draft. IMO this is something we can deal with much
later.

+        var match = propertySelectorRegExp.exec(pattern.selector);
+        if (!match)
           continue;
 
-        var propertySelectorRegExp = /\[\-abp\-properties=(["'])([^"']+)\1\]/;
-        var match = propertySelectorRegExp.exec(pattern.selector);

[kzar, 2016/11/04 15:45:56]

I guess the regexp won't necessarily match and if it doesn't we should continue
too?

[Felix Dahlke, 2016/11/04 16:43:35]

Oops, true, I'll fix that.

[Felix Dahlke, 2016/11/11 11:51:42]

Done.

+        var propertyExpression = match[2];
+        var regexpString;
+        if (propertyExpression.length >= 2 && propertyExpression[0] == "/" &&
+            propertyExpression[propertyExpression.length - 1] == "/")
+          regexpString = propertyExpression.slice(1, -1);
+        else
+          regexpString = filterToRegExp(propertyExpression);
+
         this.patterns.push({
           text: pattern.text,
-          regexp: new RegExp(filterToRegExp(match[2])),
+          regexp: new RegExp(regexpString, "i"),
           prefix: pattern.selector.substr(0, match.index),
           suffix: pattern.selector.substr(match.index + match[0].length)
         });
       }
 
       callback();
     }.bind(this));
   },
 
   apply: function()
   {
     if (this.patterns.length > 0)
     {
       var document = this.window.document;
       this.addSelectors(document.styleSheets);
       document.addEventListener("load", this.onLoad.bind(this), true);
     }
   }
 };