html2wt: Strip mw:FallbackId spans before DOM diffs

* This ensures that if an editing client strips them and sends us
  that modified DOM, we don't register a spurious diff on these
  headings.

* The blacklist changes are legitimate and are primarily because
  of dom-diff generating a slightly different dom-diff.

Bug: T195414
Change-Id: I49a656c43e32887d876e3c787cc74443f62a43f8

bin/domdiff.test.js

@@ -58,6 +58,9 @@ Promise.async(function *() {
 	var oldDOM = DU.parseHTML(oldhtml).body;
 	var newDOM = DU.parseHTML(newhtml).body;
 
+	DU.stripSectionTagsAndFallbackIds(oldDOM);
+	DU.stripSectionTagsAndFallbackIds(newDOM);
+
 	var dummyEnv = {
 		conf: { parsoid: { debug: Util.booleanOption(argv.debug) }, wiki: {} },
 		page: { id: null },

bin/parserTests.js

@@ -249,8 +249,7 @@ ParserTests.prototype.applyChanges = function(item, body, changelist) {
 		var newNode;
 
 		// Don't separate legacy IDs from their H? node.
-		if (n.nodeName === 'SPAN' &&
-			n.getAttribute('typeof') === 'mw:FallbackId') {
+		if (DU.isFallbackIdSpan(n)) {
 			n = n.nextSibling || n.parentNode;
 		}
 

bin/roundtrip-test.js

@@ -456,8 +456,8 @@ var checkIfSignificant = function(offsets, data) {
 	stripElementIds(newBody.ownerDocument.body);
 
 	// Strip section tags from the DOMs
-	DU.stripSectionTags(oldBody.ownerDocument.body);
-	DU.stripSectionTags(newBody.ownerDocument.body);
+	DU.stripSectionTagsAndFallbackIds(oldBody.ownerDocument.body);
+	DU.stripSectionTagsAndFallbackIds(newBody.ownerDocument.body);
 
 	var i, offset;
 	var results = [];

lib/html2wt/DOMHandlers.js

@@ -64,8 +64,8 @@ function buildHeadingHandler(headingWT) {
 	return {
 		forceSOL: true,
 		handle: Promise.async(function *(node, state, wrapperUnmodified) {
-			var fc = node.firstChild;
-			if (fc && DU.hasTypeOf(fc, 'mw:FallbackId')) {
+			let fc = node.firstChild;
+			if (fc && DU.isFallbackIdSpan(fc)) {
 				// Skip fallback ID if present.
 				fc = fc.nextSibling;
 			}

lib/html2wt/SelectiveSerializer.js

@@ -73,11 +73,11 @@ SelectiveSerializer.prototype.serializeDOM = Promise.async(function *(body) {
 				domDiffStart = Date.now();
 			}
 
-			// Strip <section> tags, if present.
+			// Strip <section> and mw:FallbackId <span> tags, if present.
 			// This ensures that we can accept HTML from CX / VE
 			// and other clients that might have stripped them.
-			DU.stripSectionTags(body);
-			DU.stripSectionTags(this.env.page.dom);
+			DU.stripSectionTagsAndFallbackIds(body);
+			DU.stripSectionTagsAndFallbackIds(this.env.page.dom);
 
 			diff = (new DOMDiff(this.env)).diff(this.env.page.dom, body);
 

lib/html2wt/WikitextSerializer.js

@@ -1416,7 +1416,7 @@ WS.prototype.serializeDOM = Promise.async(function *(body, selserMode) {
 	if (!selserMode) {
 		// Strip <section> tags
 		// Selser mode will have done that already before running dom-diff
-		DU.stripSectionTags(body);
+		DU.stripSectionTagsAndFallbackIds(body);
 	}
 
 	this.logType = selserMode ? "trace/selser" : "trace/wts";

lib/utils/DOMUtils.js

@@ -994,6 +994,10 @@ DU = DOMUtils = {
 		}
 	},
 
+	isFallbackIdSpan: function(node) {
+		return node.nodeName === 'SPAN' && node.getAttribute('typeof') === 'mw:FallbackId';
+	},
+
 	/**
 	 * These are primarily 'metadata'-like nodes that don't show up in output rendering.
 	 * - In Parsoid output, they are represented by link/meta tags.
@@ -1011,7 +1015,7 @@ DU = DOMUtils = {
 			DU.isSolTransparentLink(node) ||
 			// Catch-all for everything else.
 			(node.nodeName === 'META' && DU.getDataParsoid(node).stx !== 'html') ||
-			(node.nodeName === 'SPAN' && node.getAttribute('typeof') === 'mw:FallbackId');
+			DU.isFallbackIdSpan(node);
 	},
 
 	/**
@@ -2663,19 +2667,24 @@ DOMUtils.isParsoidSectionTag = function(node) {
 		node.getAttribute('data-mw-section-id') !== null;
 };
 
-DOMUtils.stripSectionTags = function(node) {
+DOMUtils.stripSectionTagsAndFallbackIds = function(node) {
 	var n = node.firstChild;
 	while (n) {
 		var next = n.nextSibling;
 		if (DU.isElt(n)) {
 			// Recurse into subtree before stripping this
-			DU.stripSectionTags(n);
+			DU.stripSectionTagsAndFallbackIds(n);
 
 			// Strip <section> tags
 			if (DU.isParsoidSectionTag(n)) {
 				DU.migrateChildren(n, n.parentNode, n);
 				DU.deleteNode(n);
 			}
+
+			// Strip <span typeof='mw:FallbackId' ...></span>
+			if (DU.isFallbackIdSpan(n)) {
+				DU.deleteNode(n);
+			}
 		}
 		n = next;
 	}

lib/wt2html/DOMPostProcessor.js

@@ -223,7 +223,7 @@ function DOMPostProcessor(env, options) {
 		// Only update headings and legacy links (first children of heading)
 		if (
 			/^H\d$/.test(node.nodeName) ||
-			node.getAttribute('typeof') === 'mw:FallbackId'
+			DU.isFallbackIdSpan(node)
 		) {
 			var suffix = 2;
 			while (this.seenIds.has(key + '_' + suffix)) {

tests/TestUtils.js

@@ -222,8 +222,7 @@ TestUtils.unwrapSpansAndNormalizeIEW = function(body, stripSpanTypeof, parsoidOn
 		// Skip over the empty mw:FallbackId <span> and strip leading WS
 		// on the other side of it.
 		if (/^H[1-6]$/.test(node.nodeName) &&
-			child && child.nodeName === 'SPAN' &&
-			child.getAttribute('typeof') === 'mw:FallbackId') {
+			child && DU.isFallbackIdSpan(child)) {
 			child = child.nextSibling;
 		}
 		for (; child; child = next) {