bugdown: Fixed emphasis regexp

static/js/echo.js

@@ -454,10 +454,9 @@ $(function () {
     marked.InlineLexer.rules.zulip.del = /^(?!<\~)\~\~([^~]+)\~\~(?!\~)/;
 
     // Disable _emphasis_
-    // Disable special characters for the emphasis syntax
-    // Inside ** allowed only: word characters/spaces/tabulate
+    // Text inside ** must start and end with a word character
     // it need for things like "const char *x = (char *)y"
-    marked.InlineLexer.rules.zulip.em = /^\*((?:\*\*|[\w|\ |\t])+?)\*(?!\*)/;
+    marked.InlineLexer.rules.zulip.em = /^\*(?!\s+)((?:\*\*|[\s\S])+?)((?:[\S]))\*(?!\*)/;
 
     // Disable autolink as (a) it is not used in our backend and (b) it interferes with @mentions
     disable_markdown_regex(marked.InlineLexer.rules.zulip, 'autolink');

static/third/marked/lib/marked.js

@@ -735,7 +735,7 @@ InlineLexer.prototype.output = function(src) {
     // em
     if (cap = this.rules.em.exec(src)) {
       src = src.substring(cap[0].length);
-      out += this.renderer.em(this.output(cap[2] || cap[1]));
+      out += this.renderer.em(cap[1] + cap[2]);
       continue;
     }
 

zerver/lib/bugdown/__init__.py

@@ -1014,12 +1014,11 @@ def extendMarkdown(self, md, md_globals):
             markdown.inlinepatterns.SimpleTagPattern(r'(?<!~)(\~\~)([^~{0}\n]+?)\2(?!~)', 'del'),
             '>strong')
 
-        # Disable special characters for the emphasis syntax
-        # Inside ** allowed only: word characters/spaces/tabulate
+        # Text inside ** must start and end with a word character
         # it need for things like "const char *x = (char *)y"
         md.inlinePatterns.add(
             'emphasis',
-            markdown.inlinepatterns.SimpleTagPattern(r'(\*)([\w|\ |\t]+)\*', 'em'),
+            markdown.inlinepatterns.SimpleTagPattern(r'(\*)(?!\s+)([^\*^\n]+)(?<!\s)\*', 'em'),
             '>strong')
 
         for k in ('hashheader', 'setextheader', 'olist', 'ulist'):