2 files changed, 46 insertions, 0 deletions
diff --git a/jstests/core/function_string_representations.js b/jstests/core/function_string_representations.js
new file mode 100644
index 00000000000..af66e9160a9
--- /dev/null
+++ b/jstests/core/function_string_representations.js
@@ -0,0 +1,38 @@
+/** Demonstrate that mapReduce can accept functions represented by strings.
+ * Some drivers do not have a type which represents a Javascript function. These languages represent
+ * the arguments to mapReduce as strings.
+ */
+
+(function() {
+    "use strict";
+
+    var col = db.function_string_representations;
+    col.drop();
+    assert.writeOK(col.insert({
+        _id: "abc123",
+        ord_date: new Date("Oct 04, 2012"),
+        status: 'A',
+        price: 25,
+        items: [{sku: "mmm", qty: 5, price: 2.5}, {sku: "nnn", qty: 5, price: 2.5}]
+    }));
+
+    var mapFunction = "function() {emit(this._id, this.price);}";
+    var reduceFunction = "function(keyCustId, valuesPrices) {return Array.sum(valuesPrices);}";
+    assert.commandWorked(col.mapReduce(mapFunction, reduceFunction, {out: "map_reduce_example"}));
+
+    // Provided strings may end with semicolons and/or whitespace
+    mapFunction += " ; ";
+    reduceFunction += " ; ";
+    assert.commandWorked(col.mapReduce(mapFunction, reduceFunction, {out: "map_reduce_example"}));
+
+    // $where exhibits the same behavior
+    var whereFunction = "function() {return this.price === 25;}";
+    assert.eq(1, col.find({$where: whereFunction}).itcount());
+
+    whereFunction += ";";
+    assert.eq(1, col.find({$where: whereFunction}).itcount());
+
+    // db.eval does not need to be tested, as it accepts code fragments, not functions.
+    // system.js does not need to be tested, as its contents types' are preserved, and
+    // strings are not promoted into functions.
+})();
diff --git a/src/mongo/scripting/mozjs/mongohelpers.js b/src/mongo/scripting/mozjs/mongohelpers.js
index b0b35bb2fe8..d3f743623a3 100644
--- a/src/mongo/scripting/mozjs/mongohelpers.js
+++ b/src/mongo/scripting/mozjs/mongohelpers.js
@@ -33,6 +33,14 @@
 exportToMongoHelpers = {
     // This function accepts an expression or function body and returns a function definition
     'functionExpressionParser': function functionExpressionParser(fnSrc) {
+
+        // Ensure that a provided expression or function body is not terminated with a ';'.
+        // This ensures we interpret the input as a single expression, rather than a sequence
+        // of expressions, and can wrap it in parentheses.
+        while (fnSrc.endsWith(";") || fnSrc != fnSrc.trimRight()) {
+            fnSrc = fnSrc.slice(0, -1).trimRight();
+        }
+
         var parseTree;
         try {
             parseTree = this.Reflect.parse(fnSrc);