show external anchor HREFs when printing (#578)

Author: michaelficarra

css/print.css

@@ -26,3 +26,8 @@ p {
 #spec-container > emu-annex {
   page-break-before: always;
 }
+
+a[data-print-href]::after {
+  content: ' <' attr(href) '>';
+  color: initial;
+}

src/Spec.ts

@@ -535,6 +535,8 @@ export default class Spec {
     }
     this.log('Propagating effect annotations...');
     this.propagateEffects();
+    this.log('Annotating external links...');
+    this.annotateExternalLinks();
     this.log('Linking xrefs...');
     this._xrefs.forEach(xref => xref.build());
     this.log('Linking non-terminal references...');
@@ -814,6 +816,14 @@ export default class Spec {
     return null;
   }
 
+  private annotateExternalLinks(): void {
+    for (const a of this.doc.getElementsByTagName('a')) {
+      if (a.hostname !== '' && a.href !== a.textContent && a.protocol !== 'mailto:') {
+        a.setAttribute('data-print-href', '');
+      }
+    }
+  }
+
   private async buildMultipage(wrapper: Element, commonEles: Element[]) {
     let stillIntro = true;
     const introEles = [];