Fix em- and en-dashes not being typographed when separated by 1 char

close https://github.com/markdown-it/markdown-it/issues/624

lib/rules_core/replacements.js

@@ -68,10 +68,10 @@ function replace_rare(inlineTokens) {
           .replace(/\.{2,}/g, '…').replace(/([?!])…/g, '$1..')
           .replace(/([?!]){4,}/g, '$1$1$1').replace(/,{2,}/g, ',')
           // em-dash
-          .replace(/(^|[^-])---([^-]|$)/mg, '$1\u2014$2')
+          .replace(/(^|[^-])---(?=[^-]|$)/mg, '$1\u2014')
           // en-dash
-          .replace(/(^|\s)--(\s|$)/mg, '$1\u2013$2')
-          .replace(/(^|[^-\s])--([^-\s]|$)/mg, '$1\u2013$2');
+          .replace(/(^|\s)--(?=\s|$)/mg, '$1\u2013')
+          .replace(/(^|[^-\s])--(?=[^-\s]|$)/mg, '$1\u2013');
       }
     }
 

test/fixtures/markdown-it/tables.txt

@@ -168,11 +168,11 @@ bar|bar
 Second line should not contain symbols except "-", ":", "|" and " ":
 .
 foo|foo
----|---s
+-----|-----s
 bar|bar
 .
 <p>foo|foo
-—|---s
+-----|-----s
 bar|bar</p>
 .
 
@@ -180,11 +180,11 @@ bar|bar</p>
 Second line should contain "|" symbol:
 .
 foo|foo
----:---
+-----:-----
 bar|bar
 .
 <p>foo|foo
-—:---
+-----:-----
 bar|bar</p>
 .
 
@@ -192,11 +192,11 @@ bar|bar</p>
 Second line should not have empty columns in the middle:
 .
 foo|foo
----||---
+-----||-----
 bar|bar
 .
 <p>foo|foo
-—||—
+-----||-----
 bar|bar</p>
 .
 
@@ -204,11 +204,11 @@ bar|bar</p>
 Wrong alignment symbol position:
 .
 foo|foo
----|-::-
+-----|-::-
 bar|bar
 .
 <p>foo|foo
-—|-::-
+-----|-::-
 bar|bar</p>
 .
 
@@ -216,11 +216,11 @@ bar|bar</p>
 Title line should contain "|" symbol:
 .
 foo
----|---
+-----|-----
 bar|bar
 .
 <p>foo
-—|---
+-----|-----
 bar|bar</p>
 .
 

test/fixtures/markdown-it/typographer.txt

@@ -79,3 +79,16 @@ markdownit--awesome
 <p>–markdownit – super–</p>
 <p>markdownit–awesome</p>
 .
+
+regression tests for #624
+.
+1---2---3
+
+1--2--3
+
+1 -- -- 3
+.
+<p>1—2—3</p>
+<p>1–2–3</p>
+<p>1 – – 3</p>
+.