[Fix] parse: when a custom decoder returns null for a key, ignore that key

Author: ljharb

lib/parse.js

@@ -108,16 +108,18 @@ var parseValues = function parseQueryStringValues(str, options) {
         } else {
             key = options.decoder(part.slice(0, pos), defaults.decoder, charset, 'key');
 
-            val = utils.maybeMap(
-                parseArrayValue(
-                    part.slice(pos + 1),
-                    options,
-                    isArray(obj[key]) ? obj[key].length : 0
-                ),
-                function (encodedVal) {
-                    return options.decoder(encodedVal, defaults.decoder, charset, 'value');
-                }
-            );
+            if (key !== null) {
+                val = utils.maybeMap(
+                    parseArrayValue(
+                        part.slice(pos + 1),
+                        options,
+                        isArray(obj[key]) ? obj[key].length : 0
+                    ),
+                    function (encodedVal) {
+                        return options.decoder(encodedVal, defaults.decoder, charset, 'value');
+                    }
+                );
+            }
         }
 
         if (val && options.interpretNumericEntities && charset === 'iso-8859-1') {
@@ -128,11 +130,13 @@ var parseValues = function parseQueryStringValues(str, options) {
             val = isArray(val) ? [val] : val;
         }
 
-        var existing = has.call(obj, key);
-        if (existing && options.duplicates === 'combine') {
-            obj[key] = utils.combine(obj[key], val);
-        } else if (!existing || options.duplicates === 'last') {
-            obj[key] = val;
+        if (key !== null) {
+            var existing = has.call(obj, key);
+            if (existing && options.duplicates === 'combine') {
+                obj[key] = utils.combine(obj[key], val);
+            } else if (!existing || options.duplicates === 'last') {
+                obj[key] = val;
+            }
         }
     }
 

test/parse.js

@@ -996,6 +996,20 @@ test('parse()', function (t) {
         st.end();
     });
 
+    t.test('handles a custom decoder returning `null`, with a string key of `null`', function (st) {
+        st.deepEqual(
+            qs.parse('null=1&ToNull=2', {
+                decoder: function (str, defaultDecoder, charset) {
+                    return str === 'ToNull' ? null : defaultDecoder(str, defaultDecoder, charset);
+                }
+            }),
+            { 'null': '1' },
+            '"null" key is not overridden by `null` decoder result'
+        );
+
+        st.end();
+    });
+
     t.test('does not interpret numeric entities in iso-8859-1 when `interpretNumericEntities` is absent', function (st) {
         st.deepEqual(qs.parse('foo=' + urlEncodedNumSmiley, { charset: 'iso-8859-1' }), { foo: '☺' });
         st.end();