Issue 2076 - Only generate element hiding filters if there are no blocking filters

lib/filterComposer.js

Index: lib/filterComposer.js
===================================================================
--- a/lib/filterComposer.js
+++ b/lib/filterComposer.js
@@ -55,11 +55,6 @@
 }
 exports.quoteCSS = quoteCSS;
 
-function canBlockURL(url)
-{
-  return url.protocol == "http:" || url.protocol == "https:";
-}
-
 /**
  * Generates filters to block an element.
  *
@@ -82,7 +77,7 @@
   for (let url of urls)
   {
     let urlObj = new URL(url, baseURL);
-    if (canBlockURL(urlObj))
+    if (urlObj.protocol == "http:" || urlObj.protocol == "https:")
     {
       let filter = stringifyURL(urlObj).replace(/^[\w\-]+:\/+(?:www\.)?/, "||");
 
@@ -91,30 +86,34 @@
     }
   }
 
-  // Generate CSS selectors based on the element's "id" and "class" attribute
+  // If we couldn't generate any blocking filters, fallback to element hiding
   let selectors = [];
-  if (id)
-    selectors.push("#" + escapeCSS(id));
-  if (classes.length > 0)
-    selectors.push(classes.map(c => "." + escapeCSS(c)).join(""));
+  if (filters.length == 0)
+  {
+    // Generate CSS selectors based on the element's "id" and "class" attribute
+    if (id)
+      selectors.push("#" + escapeCSS(id));
+    if (classes.length > 0)
+      selectors.push(classes.map(c => "." + escapeCSS(c)).join(""));
 
-  // If there is a "src" attribute, specifiying a URL that we can't block,
-  // generate a CSS selector matching the "src" attribute
-  if (src && !canBlockURL(new URL(src, baseURL)))
-    selectors.push(escapeCSS(tagName) + "[src=" + quoteCSS(src) + "]");
+    // If there is a "src" attribute, specifiying a URL that we can't block,
+    // generate a CSS selector matching the "src" attribute
+    if (src)
+      selectors.push(escapeCSS(tagName) + "[src=" + quoteCSS(src) + "]");
 
-  // As last resort, if there is a "style" attribute, and we couldn't generate
-  // any filters so far, generate a CSS selector matching the "style" attribute
-  if (style && selectors.length == 0 && filters.length == 0)
-    selectors.push(escapeCSS(tagName) + "[style=" + quoteCSS(style) + "]");
+    // As last resort, if there is a "style" attribute, and we couldn't generate
+    // any filters so far, generate a CSS selector matching the "style" attribute
+    if (style && selectors.length == 0 && filters.length == 0)
+      selectors.push(escapeCSS(tagName) + "[style=" + quoteCSS(style) + "]");
 
-  // Add an element hiding filter for each generated CSS selector
-  if (selectors.length > 0)
-  {
-    let domain = getDecodedHostname(baseURL).replace(/^www\./, "");
+    // Add an element hiding filter for each generated CSS selector
+    if (selectors.length > 0)
+    {
+      let domain = getDecodedHostname(baseURL).replace(/^www\./, "");
 
-    for (let selector of selectors)
-      filters.push(domain + "##" + selector);
+      for (let selector of selectors)
+        filters.push(domain + "##" + selector);
+    }
   }
 
   return {filters: filters, selectors: selectors};