Allow explicit inclusion of end tag to support Bixby audio (#44)

Author: rmtuckerphx

src/formatters/SamsungBixbySsmlFormatter.ts

@@ -215,7 +215,7 @@ export class SamsungBixbySsmlFormatter extends SsmlFormatterBase {
       // }
       case 'audio': {
         const url = ast.children[0].allText;
-        return this.addTagWithAttrs(lines, null, 'audio', { src: url });
+        return this.addTagWithAttrs(lines, null, 'audio', { src: url }, true);
       }
       case 'simpleLine': {
         this.processAst(ast.children, lines);

src/formatters/SsmlFormatterBase.ts

@@ -149,11 +149,15 @@ export abstract class SsmlFormatterBase extends FormatterBase {
     return '<' + tag + attrStr + '/>';
   }
 
-  protected addTagWithAttrs(lines: string[], text: string, tag: string, attrs: any): string[] {
+  protected addTagWithAttrs(lines: string[], text: string, tag: string, attrs: any, forceEndTag:boolean = false): string[] {
 
-    if (text) {
+    if (text || forceEndTag) {
       lines.push(this.startTag(tag, attrs));
-      lines.push(text);
+
+      if (text) {
+        lines.push(text);
+      }
+
       lines.push(this.endTag(tag, false));
     }
     else {

tests/audio-standard.spec.ts

@@ -54,7 +54,7 @@ describe('audio-standard', () => {
 
     const expected = dedent`
       <speak>
-      <audio src="https://www.speechmarkdown.org/test.mp3"/>
+      <audio src="https://www.speechmarkdown.org/test.mp3"></audio>
       Announcing Speech Markdown.
       </speak>
     `;
@@ -130,7 +130,7 @@ describe('audio-standard single quote', () => {
 
     const expected = dedent`
       <speak>
-      <audio src="https://www.speechmarkdown.org/test.mp3"/>
+      <audio src="https://www.speechmarkdown.org/test.mp3"></audio>
       Announcing Speech Markdown.
       </speak>
     `;
@@ -202,7 +202,7 @@ describe('audio-standard soundbank', () => {
 
     const expected = dedent`
       <speak>
-      <audio src="soundbank://soundlibrary/alarms/air_horns/air_horn_01"/> Air horn
+      <audio src="soundbank://soundlibrary/alarms/air_horns/air_horn_01"></audio> Air horn
       </speak>
     `;