Tolerate spaces after language in markdown fences.

See #2357.  We now support `~~~ .py ` with that trailing space.

Note that the test coverage is Python-side only due to
bugdown_matches_marked being set to false, since we don't yet
support language syntax on the client side.

(imported from commit ccd5fcb0eee01478d349161400103480678d7486)

static/js/fenced_code.js

@@ -15,6 +15,7 @@ var fencestr = "^(~{3,}|`{3,})"          + // Opening Fence
                    "\\{?\\.?"            +
                    "([a-zA-Z0-9_+-]*)"   + // Language
                    "\\}?"                +
+               "[ ]*"                    + // Spaces
                ")$";
 var fence_re = new RegExp(fencestr);
 

zerver/fixtures/bugdown-data.json

@@ -2,7 +2,7 @@
   "regular_tests": [
     {
       "name": "codeblock_hilite",
-      "input": "Hamlet said:\n~~~~.python\ndef speak(self):\n    x = 1\n~~~~",
+      "input": "Hamlet said:\n~~~~.python \ndef speak(self):\n    x = 1\n~~~~",
       "expected_output": "<p>Hamlet said:</p>\n<div class=\"codehilite\"><pre><span class=\"k\">def</span> <span class=\"nf\">speak</span><span class=\"p\">(</span><span class=\"bp\">self</span><span class=\"p\">):</span>\n    <span class=\"n\">x</span> <span class=\"o\">=</span> <span class=\"mi\">1</span>\n</pre></div>",
       "bugdown_matches_marked": false
     },
@@ -574,4 +574,4 @@
       "http://generate.quora.net/render?width=700&amp;from=-4hours&amp;until=now&amp;height=400&amp;bgcolor=black&amp;lineMode=connected&amp;title=arb%20hint%20status&amp;target=alias(ans.hintland.hand.arb.enhint_rate%2C%22enhint%20rate%22)&amp;target=alias(ans.hintland.hand.arb.unhint_rate%2C%22unhint%20rate%22)&amp;target=alias(ans.hintland.hand.arb.size%2C%22hint%20size%22)&amp;target=alias(scale(ans.vagabond.dingarb_cube_count%2C10000)%2C%22cube%20count%20x%2010K%22)&amp;target=alias(scale(hnumbers.time.ding.gegevens.query.count%2C10)%2C%22ding%20gegevens%20query%20count%20x%2010%22)&amp;fgcolor=white&amp;uniq=0.44046106841415167"
     ]
   ]
-}
+}

zerver/lib/bugdown/fenced_code.py

@@ -83,6 +83,7 @@ FENCE_RE = re.compile(r"""
         ) # "py" or "javascript"
         \}?
     ) # language, like ".py" or "{javascript}"
+    [ ]* # spaces
     $
     """, re.VERBOSE)