From e85cb97ccaf1b71908d84bd499b1a491bace5d16 Mon Sep 17 00:00:00 2001
From: Ron Kok <ronkok@comcast.net>
Date: Tue, 1 Jan 2019 09:13:54 -0800
Subject: [PATCH] Fix \genfrac w/empty delimiter arguments (#1816)

---
 src/functions/genfrac.js | 12 ++++--------
 test/katex-spec.js       |  2 ++
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/src/functions/genfrac.js b/src/functions/genfrac.js
index 05142624..26078d81 100644
--- a/src/functions/genfrac.js
+++ b/src/functions/genfrac.js
@@ -363,21 +363,17 @@ defineFunction({
         const denom = args[5];
 
         // Look into the parse nodes to get the desired delimiters.
-        let leftNode = checkNodeType(args[0], "ordgroup");
+        let leftNode = checkNodeType(args[0], "atom");
         if (leftNode) {
-            leftNode = assertAtomFamily(leftNode.body[0], "open");
-        } else {
             leftNode = assertAtomFamily(args[0], "open");
         }
-        const leftDelim = delimFromValue(leftNode.text);
+        const leftDelim = leftNode ? delimFromValue(leftNode.text) : null;
 
-        let rightNode = checkNodeType(args[1], "ordgroup");
+        let rightNode = checkNodeType(args[1], "atom");
         if (rightNode) {
-            rightNode = assertAtomFamily(rightNode.body[0], "close");
-        } else {
             rightNode = assertAtomFamily(args[1], "close");
         }
-        const rightDelim = delimFromValue(rightNode.text);
+        const rightDelim = rightNode ? delimFromValue(rightNode.text) : null;
 
         const barNode = assertNodeType(args[2], "size");
         let hasBarLine;
diff --git a/test/katex-spec.js b/test/katex-spec.js
index 1f49cff2..00ea68e9 100644
--- a/test/katex-spec.js
+++ b/test/katex-spec.js
@@ -646,6 +646,8 @@ describe("A genfrac builder", function() {
         expect("\\cfrac{x}{y}").toBuild();
         expect("\\genfrac ( ] {0.06em}{0}{a}{b+c}").toBuild();
         expect("\\genfrac ( ] {0.8pt}{}{a}{b+c}").toBuild();
+        expect("\\genfrac {} {} {0.8pt}{}{a}{b+c}").toBuild();
+        expect("\\genfrac [ {} {0.8pt}{}{a}{b+c}").toBuild();
     });
 });