Update MD037 to handle violations at the start/end of a line.

lib/md037.js

@@ -11,10 +11,10 @@ module.exports = {
   "function": function MD037(params, onError) {
     shared.forEachInlineChild(params, "text", function forToken(token) {
       let left = true;
-      let match = /\s(\*\*?|__?)\s.+\1/.exec(token.content);
+      let match = /(?:^|\s)(\*\*?|__?)\s.+\1/.exec(token.content);
       if (!match) {
         left = false;
-        match = /(\*\*?|__?).+\s\1\s/.exec(token.content);
+        match = /(\*\*?|__?).+\s\1(?:\s|$)/.exec(token.content);
       }
       if (match) {
         const text = match[0].trim();

test/spaces_inside_emphasis_markers.md

@@ -1,3 +1,5 @@
+# Heading
+
 Line with *Normal emphasis*
 
 Line with **Normal strong**
@@ -33,3 +35,35 @@ One-sided * broken emphasis* {MD037}
 Don't _flag on _words with underscores before them.
 
 The same goes for words* with asterisks* after them.
+
+* Emphasis* with left space is recognized as a list
+
+** Strong** with left space {MD037}
+
+_ Emphasis_ with left space {MD037}
+
+__ Strong__ with left space {MD037}
+
+*Emphasis * with right space {MD037}
+
+**Strong ** with right space {MD037}
+
+_Emphasis _ with right space {MD037}
+
+__Strong __ with right space {MD037}
+
+{MD037} Left space * emphasis*
+
+{MD037} Left space ** strong**
+
+{MD037} Left space _ emphasis_
+
+{MD037} Left space __ strong__
+
+{MD037} Right space *emphasis *
+
+{MD037} Right space **strong **
+
+{MD037} Right space _emphasis _
+
+{MD037} Right space __strong __