feat(tag/post_link): throw on post_link error

lib/plugins/tag/post_link.js

@@ -12,9 +12,10 @@ const { postFindOneFactory } = require('./');
  */
 module.exports = ctx => {
   return function postLinkTag(args) {
-    const error = `<a href="#">Post not found: ${args.join(' ') || 'Invalid post_link'}</a>`;
     const slug = args.shift();
-    if (!slug) return error;
+    if (!slug) {
+      throw new Error('Post not found: no slug for post_link.');
+    }
 
     let escape = args[args.length - 1];
     if (escape === 'true' || escape === 'false') {
@@ -24,7 +25,9 @@ module.exports = ctx => {
     }
 
     const post = postFindOneFactory(ctx)({ slug });
-    if (!post) return error;
+    if (!post) {
+      throw new Error(`Post not found: post_link ${slug}.`);
+    }
 
     let title = args.length ? args.join(' ') : post.title;
     const attrTitle = escapeHTML(title);

test/scripts/tags/post_link.js

@@ -57,11 +57,11 @@ describe('post_link', () => {
       .should.eql('<a href="/title-with-tag/" title="This is a &lt;b&gt;Bold&lt;&#x2F;b&gt; &quot;statement&quot;">This is a <b>Bold</b> "statement"</a>');
   });
 
-  it('no slug', () => {
-    postLink([]).should.eql('<a href="#">Post not found: Invalid post_link</a>');
+  it('should throw if no slug', () => {
+    should.throw(() => postLink([]), Error, /Post not found: no slug for post_link\./);
   });
 
-  it('post not found', () => {
-    postLink(['bar']).should.eql('<a href="#">Post not found: bar</a>');
+  it('should throw if post not found', () => {
+    should.throw(() => postLink(['bar']), Error, /Post not found: post_link bar\./);
   });
 });