From d59f02f622fbe757375577720186017a5611a0e4 Mon Sep 17 00:00:00 2001
From: Matt Sacks <matt.s.sacks@gmail.com>
Date: Sat, 6 Oct 2012 06:28:41 -0700
Subject: [PATCH] Don't evaluate lambdas that return falsy values as an empty
 string.

Issue: If I create a Mustache lambda to return numbers and I expect 0 to be of
those numbers, I'll instead only receive an empty string for 0 because it
evaluates to falsy.

Fix: Check the result of the lambda to be undefined or null. Only then should
it return the empty string.
---
 mustache.js                      | 3 ++-
 test/_files/check_falsy.js       | 7 +++++++
 test/_files/check_falsy.mustache | 1 +
 test/_files/check_falsy.txt      | 1 +
 4 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 test/_files/check_falsy.js
 create mode 100644 test/_files/check_falsy.mustache
 create mode 100644 test/_files/check_falsy.txt

diff --git a/mustache.js b/mustache.js
index 7165a8a..582a29c 100644
--- a/mustache.js
+++ b/mustache.js
@@ -254,7 +254,8 @@ var Mustache;
         return self.render(template, context);
       };
 
-      return value.call(context.view, text, scopedRender) || "";
+      var result = value.call(context.view, text, scopedRender);
+      return result != null ? result : "";
     default:
       if (value) {
         return callback(this, context);
diff --git a/test/_files/check_falsy.js b/test/_files/check_falsy.js
new file mode 100644
index 0000000..5a599ca
--- /dev/null
+++ b/test/_files/check_falsy.js
@@ -0,0 +1,7 @@
+({
+  number: function(text, render) {
+    return function(text, render) {
+      return +render(text);
+    }
+  }
+})
diff --git a/test/_files/check_falsy.mustache b/test/_files/check_falsy.mustache
new file mode 100644
index 0000000..30e2547
--- /dev/null
+++ b/test/_files/check_falsy.mustache
@@ -0,0 +1 @@
+<p>{{#number}}0{{/number}}</p>
diff --git a/test/_files/check_falsy.txt b/test/_files/check_falsy.txt
new file mode 100644
index 0000000..3bb2f51
--- /dev/null
+++ b/test/_files/check_falsy.txt
@@ -0,0 +1 @@
+<p>0</p>