Fix boolean attribute hadling s.t. it doesnt have 'undefined' value (#40)

- While there I also updated handling of children/attributes to allow
  them to be empty. This improves efficiency over the wire.

Author: samouri

src/ast.ts

@@ -45,15 +45,25 @@ export function fromNode(node: Node): NodeProto {
   }
 
   const elementNode = node as Element;
-  const attributes = Array.from(elementNode.attributes).map(
-    ({name, value}) => ({name, value})
-  );
-  return {
+  const protoNode: NodeProto = {
     tagid: getTagId(elementNode.tagName),
     value: elementNode.tagName.toLowerCase(),
-    attributes,
-    children: Array.from(node.childNodes).map(fromNode),
   };
+
+  if (elementNode.attributes?.length) {
+    protoNode.attributes = Array.from(elementNode.attributes).map(
+      ({name, value}) => {
+        if (value === '') {
+          return {name};
+        }
+        return {name, value};
+      }
+    );
+  }
+  if (node.childNodes?.length) {
+    protoNode.children = Array.from(node.childNodes).map(fromNode);
+  }
+  return protoNode;
 }
 
 const termRegex = /[\w-]+/gm;

src/dom.ts

@@ -70,11 +70,19 @@ function fromTreeProtoHelper(nodes: NodeProto[], doc: Document, parent: Node) {
     }
 
     const domNode = doc.createElement(node.value);
-    for (const {name, value} of node.attributes) {
-      domNode.setAttribute(name, value);
+    if (node.attributes) {
+      for (const {name, value} of node.attributes) {
+        if (typeof value === 'undefined') {
+          domNode.setAttribute(name, '');
+        } else {
+          domNode.setAttribute(name, value);
+        }
+      }
     }
     parent.appendChild(domNode);
 
-    fromTreeProtoHelper(node.children, doc, domNode);
+    if (node.children) {
+      fromTreeProtoHelper(node.children, doc, domNode);
+    }
   }
 }

src/protos.ts

@@ -19,8 +19,8 @@ export interface TextNodeProto {
 export interface ElementNodeProto {
   tagid: number;
   value: string;
-  attributes: Array<AttributeProto>;
-  children: Array<NodeProto>;
+  attributes?: Array<AttributeProto>;
+  children?: Array<NodeProto>;
 }
 
 export interface AttributeProto {

test/test-index.ts

@@ -14,7 +14,12 @@
  * limitations under the License.
  */
 import test from 'ava';
-import {DocumentNodeProto, NodeProto, TreeProto} from '../src/protos.js';
+import {
+  DocumentNodeProto,
+  ElementNodeProto,
+  NodeProto,
+  TreeProto,
+} from '../src/protos.js';
 import {getTagId} from '../src/htmltagenum.js';
 import {renderAstDocument, renderAstNodes} from '../src/index.js';
 
@@ -26,20 +31,30 @@ function h(
   attributes: Object = {},
   children: Array<NodeProto | string> = []
 ): NodeProto {
-  return {
+  const nodeProto: NodeProto = {
     tagid: getTagId(tagName),
     value: tagName,
-    attributes: Object.entries(attributes).map(([name, value]) => ({
-      name,
-      value,
-    })),
-    children: children.map((child) => {
+  };
+  if (Object.entries(attributes).length) {
+    nodeProto.attributes = Object.entries(attributes).map(([name, value]) => {
+      if (value === '') {
+        return {name};
+      }
+      return {
+        name,
+        value,
+      };
+    });
+  }
+  if (children.length) {
+    nodeProto.children = children.map((child) => {
       if (typeof child === 'string') {
         return {value: child, num_terms: child.match(/[\w]+/gm)?.length ?? 0};
       }
       return child;
-    }),
-  };
+    });
+  }
+  return nodeProto;
 }
 
 /**
@@ -164,6 +179,28 @@ test('should conserve quirks_mode and root', (t) => {
   t.deepEqual(renderAstDocument(ast, {}), ast);
 });
 
+test('should conserve boolean attributes', (t) => {
+  const tree: [DocumentNodeProto] = [
+    {
+      tagid: 92,
+      children: [{tagid: 43, value: 'html', attributes: [{name: 'amp'}]}],
+    },
+  ];
+  const ast: TreeProto = {root: 42, quirks_mode: true, tree};
+  t.deepEqual(renderAstDocument(ast, {}), ast);
+});
+
+test('should conserve lack of children/attrs for efficiency', (t) => {
+  const tree: [DocumentNodeProto] = [
+    {
+      tagid: 92,
+      children: [{tagid: 43, value: 'html'}],
+    },
+  ];
+  const ast: TreeProto = {root: 42, quirks_mode: true, tree};
+  t.deepEqual(renderAstDocument(ast, {}), ast);
+});
+
 test('should set tagids of element nodes', (t) => {
   function buildAmpList(element) {
     const b = element.ownerDocument.createElement('b');