Fix the newline workarounds (for Parsoid newline handling) for headings

* Parsoid outputs bare newlines after a heading unless it's followed by
  a <p>, so strip leading and trailing newlines in all bare text
* Adding a leading newline in <p>s is only needed if preceded by a
  heading, don't add it otherwise
* Headings need a bare newline after them unless followed by a <p>
* Headings also need a bare newline before them if preceded by a <pre>

Change-Id: Ib02f800b26453541604e920fbb3845c51cdc6dea

Author: catrope

modules/ve2/dm/ve.dm.Converter.js

@@ -301,6 +301,7 @@ ve.dm.Converter.prototype.getDataFromDom = function( domElement, annotations, da
 					text = text.replace( /\n+$/, '' );
 				}
 				if ( text === '' ) {
+					// Don't produce an empty text node or an empty paragraph
 					break;
 				}
 				// HACK: strip implied leading and trailing newlines in <p> tags
@@ -339,6 +340,15 @@ ve.dm.Converter.prototype.getDataFromDom = function( domElement, annotations, da
 					}
 				}
 
+				if ( !branchIsContent ) {
+					// If it's bare content, strip leading and trailing newlines
+					text = text.replace( /^\n+/, '' ).replace( /\n+$/, '' );
+					if ( text === '' ) {
+						// Don't produce an empty text node
+						break;
+					}
+				}
+
 				// Start auto-wrapping of bare content
 				if ( !wrapping && !alreadyWrapped && !branchIsContent ) {
 					data.push( { 'type': 'paragraph' } );
@@ -379,9 +389,8 @@ ve.dm.Converter.prototype.getDomFromData = function( data ) {
 		// This reverses the newline stripping done in getDataFromDom()
 		/*
 		 * Leading newlines:
-		 * If the previous sibling is a paragraph, do not add any leading newlines
-		 * If there is no previous sibling, do not add any leading newlines
-		 * Otherwise, add 1 leading newline
+		 * If the previous sibling is a heading, add 1 leading newline
+		 * Otherwise, do not add any leading newlines
 		 *
 		 * Trailing newlines:
 		 * If the next sibling is a paragraph, add 2 trailing newlines
@@ -391,7 +400,7 @@ ve.dm.Converter.prototype.getDomFromData = function( data ) {
 		if ( node.nodeName.toLowerCase() === 'p' ) {
 			if (
 				node.previousSibling &&
-				node.previousSibling.nodeName.toLowerCase() !== 'p'
+				node.previousSibling.nodeName.toLowerCase().match( /h\d/ )
 			) {
 				text = "\n" + text;
 			}
@@ -583,6 +592,19 @@ ve.dm.Converter.prototype.getDomFromData = function( data ) {
 		.each( function() {
 			this.data = fixupText( this.data, this.parentNode );
 		} );
+	// And add newlines after headings too
+	$( container ).find( 'h1, h2, h3, h4, h5, h6' ).each( function() {
+		// If there is no next sibling, we don't need to add a newline
+		// If the next sibling is a paragraph, fixupText() has taken care of it
+		// Otherwise, add a newline after the heading
+		if ( this.nextSibling && this.nextSibling.nodeName.toLowerCase() !== 'p' ) {
+			this.parentNode.insertBefore( document.createTextNode( "\n" ), this.nextSibling );
+		}
+		// If the previous sibling exists and is a pre, we need to add a newline before
+		if ( this.previousSibling && this.previousSibling.nodeName.toLowerCase() === 'pre' ) {
+			this.parentNode.insertBefore( document.createTextNode( "\n" ), this );
+		}
+	} );
 	return container;
 };