Ensure IDL blocks are omitted from the dev edition

The existing wattsi code for causing IDL blocks to be omitted from the dev edition quit working when whatwg/html#3768 moved class=idl attributes off `pre` elements and instead onto to `code` children of those elements,

So the first part of this change causes those `code class=idl` elements to be dropped as expected. But as a result of that, the now-empty `pre` element parents of those `code` elements are left behind. So the second part of this change looks for those empty `pre` elements and drops them.

This change reverts the e1e3599 revert that was made because — as initially implemented in c13e47b — stray `</pre>` end tags got left behind for all `pre` elements that were omitted. This change corrects that problem (it ensures the end tags get removed as expected).

Fixes #84.

src/wattsi.pas

@@ -643,6 +643,11 @@    TCrossReferences = record
          Element := TElement(Node);
          if (Element.HasAttribute('class')) then
             ClassValue := Element.GetAttribute('class').AsString;
+         if (IsHighlighterTarget(Element, ClassValue) and AnsiContainsStr(ClassValue, 'idl') and (Variant = vDEV)) then
+         begin
+            Result := False;
+         end
+         else
          if (Element.HasProperties(propHeading)) then
          begin
             ClassName := Element.GetAttribute('class').AsString;
@@ -970,11 +975,6 @@    TCrossReferences = record
             SaveCrossReference(Element);
          end
          else
-         if (IsHighlighterTarget(Element, ClassValue) and AnsiContainsStr(ClassValue, 'idl') and (Variant = vDEV)) then
-         begin
-            Result := False;
-         end
-         else
          if (Element.isIdentity(nsHTML, eA) and (Element.GetAttribute('class').AsString = 'sha-link') and (Variant = vSnap)) then
          begin
             Element.AppendChild(TText.Create(SourceGitSHA));
@@ -1856,6 +1856,12 @@ procedure Save(const Document: TDocument; const FileName: AnsiString; const InSp
       Quotes: TQuoteType;
       Variant: TAllVariants;
    begin
+      // The following causes the <pre> start tag for any empty pre elements to
+      // be dropped. We can end up with empty pre elements because the first
+      // pass may drop <code class="idl"> elements from the dev edition, leaving
+      // behind the (now-empty) pre parents of the <code class="idl"> elements.
+      if Element.IsIdentity(nsHTML, ePre) and (Element.TextContent.AsString = '') then
+         exit;
       IsExcluder := DetermineIsExcluder(Element, AttributeCount);
       if ((not IsExcluder) and ((AttributeCount > 0) or (not (Element.HasProperties(propOptionalStartTag) or SkippableTBodyStartTag(Element))))) then
       begin
@@ -1928,6 +1934,12 @@ procedure Save(const Document: TDocument; const FileName: AnsiString; const InSp
       HighlighterOutput: String;
       ClassValue: String = '';
    begin
+      // The following causes the </pre> end tag for any empty pre elements to
+      // be dropped. We can end up with empty pre elements because the first
+      // pass may drop <code class="idl"> elements from the dev edition, leaving
+      // behind the (now-empty) pre parents of the <code class="idl"> elements.
+      if Element.IsIdentity(nsHTML, ePre) and (Element.TextContent.AsString = '') then
+         exit;
       if (InSplit and Element.HasAttribute(kExcludingAttribute[vSplit])) then
          exit;
       IsExcluder := DetermineIsExcluder(Element, AttributeCount);