From e03a80dccc8b88388e79725d9c98568559555ae7 Mon Sep 17 00:00:00 2001
From: Regev Brody <regevbr@gmail.com>
Date: Fri, 19 Jun 2020 01:37:24 +0300
Subject: [PATCH] feat: underline markdown support (#2073)

* fix: no markdown support for underline #2072
---
 client/components/editor/editor-markdown.vue         |  2 ++
 client/libs/markdown-it-underline/index.js           | 12 ++++++++++++
 .../modules/rendering/markdown-core/definition.yml   |  9 ++++++++-
 server/modules/rendering/markdown-core/renderer.js   |  5 +++++
 server/modules/rendering/markdown-core/underline.js  | 12 ++++++++++++
 5 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 client/libs/markdown-it-underline/index.js
 create mode 100644 server/modules/rendering/markdown-core/underline.js

diff --git a/client/components/editor/editor-markdown.vue b/client/components/editor/editor-markdown.vue
index 95b99ce2..1b1c483b 100644
--- a/client/components/editor/editor-markdown.vue
+++ b/client/components/editor/editor-markdown.vue
@@ -220,6 +220,7 @@ import mdMark from 'markdown-it-mark'
 import mdFootnote from 'markdown-it-footnote'
 import mdImsize from 'markdown-it-imsize'
 import katex from 'katex'
+import underline from '../../libs/markdown-it-underline'
 import 'katex/dist/contrib/mhchem'
 import twemoji from 'twemoji'
 import plantuml from './markdown/plantuml'
@@ -268,6 +269,7 @@ const md = new MarkdownIt({
   .use(mdAttrs, {
     allowedAttributes: ['id', 'class', 'target']
   })
+  .use(underline)
   .use(mdEmoji)
   .use(mdTaskLists, {label: true, labelAfter: true})
   .use(mdExpandTabs)
diff --git a/client/libs/markdown-it-underline/index.js b/client/libs/markdown-it-underline/index.js
new file mode 100644
index 00000000..c840ea0b
--- /dev/null
+++ b/client/libs/markdown-it-underline/index.js
@@ -0,0 +1,12 @@
+const renderEm = (tokens, idx, opts, env, slf) => {
+  const token = tokens[idx];
+  if (token.markup === '_') {
+    token.tag = 'u';
+  }
+  return slf.renderToken(tokens, idx, opts);
+}
+
+module.exports = (md) => {
+  md.renderer.rules.em_open = renderEm;
+  md.renderer.rules.em_close = renderEm;
+}
diff --git a/server/modules/rendering/markdown-core/definition.yml b/server/modules/rendering/markdown-core/definition.yml
index 1dd91a1d..b7ccab9a 100644
--- a/server/modules/rendering/markdown-core/definition.yml
+++ b/server/modules/rendering/markdown-core/definition.yml
@@ -34,12 +34,19 @@ props:
     hint: Enable some language-neutral replacement + quotes beautification
     order: 4
     public: true
+  underline:
+    type: Boolean
+    default: false
+    title: Underline Support
+    hint: Enable underline by using _underline_
+    order: 5
+    public: true
   quotes:
     type: String
     default: English
     title: Quotes style
     hint: When typographer is enabled. Double + single quotes replacement pairs. e.g. «»„“ for Russian, „“‚‘ for German, etc.
-    order: 5
+    order: 6
     enum:
       - Chinese
       - English
diff --git a/server/modules/rendering/markdown-core/renderer.js b/server/modules/rendering/markdown-core/renderer.js
index 40632026..ef8cd5f0 100644
--- a/server/modules/rendering/markdown-core/renderer.js
+++ b/server/modules/rendering/markdown-core/renderer.js
@@ -1,6 +1,7 @@
 const md = require('markdown-it')
 const mdAttrs = require('markdown-it-attrs')
 const _ = require('lodash')
+const underline = require('./underline')
 
 const quoteStyles = {
   Chinese: '””‘’',
@@ -30,6 +31,10 @@ module.exports = {
       }
     })
 
+    if (this.config.underline) {
+      mkdown.use(underline)
+    }
+
     mkdown.use(mdAttrs, {
       allowedAttributes: ['id', 'class', 'target']
     })
diff --git a/server/modules/rendering/markdown-core/underline.js b/server/modules/rendering/markdown-core/underline.js
new file mode 100644
index 00000000..c840ea0b
--- /dev/null
+++ b/server/modules/rendering/markdown-core/underline.js
@@ -0,0 +1,12 @@
+const renderEm = (tokens, idx, opts, env, slf) => {
+  const token = tokens[idx];
+  if (token.markup === '_') {
+    token.tag = 'u';
+  }
+  return slf.renderToken(tokens, idx, opts);
+}
+
+module.exports = (md) => {
+  md.renderer.rules.em_open = renderEm;
+  md.renderer.rules.em_close = renderEm;
+}