[New] parse/stringify: add allowEmptyArrays option to allow [] in object values

.eslintrc

@@ -14,7 +14,7 @@
         "id-length": [2, { "min": 1, "max": 25, "properties": "never" }],
         "indent": [2, 4],
         "max-lines-per-function": [2, { "max": 150 }],
-        "max-params": [2, 16],
+        "max-params": [2, 17],
         "max-statements": [2, 100],
         "multiline-comment-style": 0,
         "no-continue": 1,

README.md

@@ -149,6 +149,12 @@ var withDots = qs.parse('a.b=c', { allowDots: true });
 assert.deepEqual(withDots, { a: { b: 'c' } });
 ```
 
+Option `allowEmptyArrays` can be used to allowing empty array values in object
+```javascript
+var withEmptyArrays = qs.parse('foo[]&bar=baz', { allowEmptyArrays: true });
+assert.deepEqual(withEmptyArrays, { foo: [], bar: 'baz' });
+```
+
 If you have to deal with legacy browsers or services, there's
 also support for decoding percent-encoded octets as iso-8859-1:
 
@@ -420,6 +426,12 @@ qs.stringify({ a: { b: { c: 'd', e: 'f' } } }, { allowDots: true });
 // 'a.b.c=d&a.b.e=f'
 ```
 
+You may allow empty array values by setting the `allowEmptyArrays` option to `true`:
+```javascript
+qs.stringify({ foo: [], bar: 'baz' }, { allowEmptyArrays: true });
+// 'foo[]&bar=baz'
+```
+
 Empty strings and null values will omit the value, but the equals sign (=) remains in place:
 
 ```javascript

lib/parse.js

@@ -7,6 +7,7 @@ var isArray = Array.isArray;
 
 var defaults = {
     allowDots: false,
+    allowEmptyArrays: false,
     allowPrototypes: false,
     allowSparse: false,
     arrayLimit: 20,
@@ -121,7 +122,7 @@ var parseObject = function (chain, val, options, valuesParsed) {
         var root = chain[i];
 
         if (root === '[]' && options.parseArrays) {
-            obj = [].concat(leaf);
+            obj = options.allowEmptyArrays && leaf === '' ? [] : [].concat(leaf);
         } else {
             obj = options.plainObjects ? Object.create(null) : {};
             var cleanRoot = root.charAt(0) === '[' && root.charAt(root.length - 1) === ']' ? root.slice(1, -1) : root;
@@ -207,7 +208,11 @@ var normalizeParseOptions = function normalizeParseOptions(opts) {
         return defaults;
     }
 
-    if (opts.decoder !== null && opts.decoder !== undefined && typeof opts.decoder !== 'function') {
+    if (typeof opts.allowEmptyArrays !== 'undefined' && typeof opts.allowEmptyArrays !== 'boolean') {
+        throw new TypeError('`allowEmptyArrays` option can only be `true` or `false`, when provided');
+    }
+
+    if (opts.decoder !== null && typeof opts.decoder !== 'undefined' && typeof opts.decoder !== 'function') {
         throw new TypeError('Decoder has to be a function.');
     }
 
@@ -218,6 +223,7 @@ var normalizeParseOptions = function normalizeParseOptions(opts) {
 
     return {
         allowDots: typeof opts.allowDots === 'undefined' ? defaults.allowDots : !!opts.allowDots,
+        allowEmptyArrays: typeof opts.allowEmptyArrays === 'boolean' ? !!opts.allowEmptyArrays : defaults.allowEmptyArrays,
         allowPrototypes: typeof opts.allowPrototypes === 'boolean' ? opts.allowPrototypes : defaults.allowPrototypes,
         allowSparse: typeof opts.allowSparse === 'boolean' ? opts.allowSparse : defaults.allowSparse,
         arrayLimit: typeof opts.arrayLimit === 'number' ? opts.arrayLimit : defaults.arrayLimit,

lib/stringify.js

@@ -30,6 +30,7 @@ var defaultFormat = formats['default'];
 var defaults = {
     addQueryPrefix: false,
     allowDots: false,
+    allowEmptyArrays: false,
     arrayFormat: 'indices',
     charset: 'utf-8',
     charsetSentinel: false,
@@ -63,6 +64,7 @@ var stringify = function stringify(
     prefix,
     generateArrayPrefix,
     commaRoundTrip,
+    allowEmptyArrays,
     strictNullHandling,
     skipNulls,
     encoder,
@@ -148,6 +150,10 @@ var stringify = function stringify(
 
     var adjustedPrefix = commaRoundTrip && isArray(obj) && obj.length === 1 ? prefix + '[]' : prefix;
 
+    if (allowEmptyArrays && isArray(obj) && obj.length === 0) {
+        return adjustedPrefix + '[]';
+    }
+
     for (var j = 0; j < objKeys.length; ++j) {
         var key = objKeys[j];
         var value = typeof key === 'object' && typeof key.value !== 'undefined' ? key.value : obj[key];
@@ -168,6 +174,7 @@ var stringify = function stringify(
             keyPrefix,
             generateArrayPrefix,
             commaRoundTrip,
+            allowEmptyArrays,
             strictNullHandling,
             skipNulls,
             generateArrayPrefix === 'comma' && encodeValuesOnly && isArray(obj) ? null : encoder,
@@ -191,6 +198,10 @@ var normalizeStringifyOptions = function normalizeStringifyOptions(opts) {
         return defaults;
     }
 
+    if (typeof opts.allowEmptyArrays !== 'undefined' && typeof opts.allowEmptyArrays !== 'boolean') {
+        throw new TypeError('`allowEmptyArrays` option can only be `true` or `false`, when provided');
+    }
+
     if (opts.encoder !== null && typeof opts.encoder !== 'undefined' && typeof opts.encoder !== 'function') {
         throw new TypeError('Encoder has to be a function.');
     }
@@ -230,6 +241,7 @@ var normalizeStringifyOptions = function normalizeStringifyOptions(opts) {
     return {
         addQueryPrefix: typeof opts.addQueryPrefix === 'boolean' ? opts.addQueryPrefix : defaults.addQueryPrefix,
         allowDots: typeof opts.allowDots === 'undefined' ? defaults.allowDots : !!opts.allowDots,
+        allowEmptyArrays: typeof opts.allowEmptyArrays === 'boolean' ? !!opts.allowEmptyArrays : defaults.allowEmptyArrays,
         arrayFormat: arrayFormat,
         charset: charset,
         charsetSentinel: typeof opts.charsetSentinel === 'boolean' ? opts.charsetSentinel : defaults.charsetSentinel,
@@ -292,6 +304,7 @@ module.exports = function (object, opts) {
             key,
             generateArrayPrefix,
             commaRoundTrip,
+            options.allowEmptyArrays,
             options.strictNullHandling,
             options.skipNulls,
             options.encode ? options.encoder : null,

test/parse.js

@@ -72,6 +72,37 @@ test('parse()', function (t) {
     t.test('allows enabling dot notation', function (st) {
         st.deepEqual(qs.parse('a.b=c'), { 'a.b': 'c' });
         st.deepEqual(qs.parse('a.b=c', { allowDots: true }), { a: { b: 'c' } });
+
+        st.end();
+    });
+
+    t.test('allows empty arrays in obj values', function (st) {
+        st.deepEqual(qs.parse('foo[]&bar=baz', { allowEmptyArrays: true }), { foo: [], bar: 'baz' });
+        st.deepEqual(qs.parse('foo[]&bar=baz', { allowEmptyArrays: false }), { foo: [''], bar: 'baz' });
+
+        st.end();
+    });
+
+    t.test('should throw when allowEmptyArrays is not of type boolean', function (st) {
+        st['throws'](
+            function () { qs.parse('foo[]&bar=baz', { allowEmptyArrays: 'foobar' }); },
+            TypeError
+        );
+
+        st['throws'](
+            function () { qs.parse('foo[]&bar=baz', { allowEmptyArrays: 0 }); },
+            TypeError
+        );
+        st['throws'](
+            function () { qs.parse('foo[]&bar=baz', { allowEmptyArrays: NaN }); },
+            TypeError
+        );
+
+        st['throws'](
+            function () { qs.parse('foo[]&bar=baz', { allowEmptyArrays: null }); },
+            TypeError
+        );
+
         st.end();
     });
 

test/stringify.js

@@ -140,6 +140,45 @@ test('stringify()', function (t) {
 
     t.test('omits array indices when asked', function (st) {
         st.equal(qs.stringify({ a: ['b', 'c', 'd'] }, { indices: false }), 'a=b&a=c&a=d');
+
+        st.end();
+    });
+
+    t.test('omits object key/value pair when value is empty array', function (st) {
+        st.equal(qs.stringify({ a: [], b: 'zz' }), 'b=zz');
+
+        st.end();
+    });
+
+    t.test('should not omit object key/value pair when value is empty array and when asked', function (st) {
+        st.equal(qs.stringify({ a: [], b: 'zz' }), 'b=zz');
+        st.equal(qs.stringify({ a: [], b: 'zz' }, { allowEmptyArrays: false }), 'b=zz');
+        st.equal(qs.stringify({ a: [], b: 'zz' }, { allowEmptyArrays: true }), 'a[]&b=zz');
+
+        st.end();
+    });
+
+    t.test('should throw when allowEmptyArrays is not of type boolean', function (st) {
+        st['throws'](
+            function () { qs.stringify({ a: [], b: 'zz' }, { allowEmptyArrays: 'foobar' }); },
+            TypeError
+        );
+
+        st['throws'](
+            function () { qs.stringify({ a: [], b: 'zz' }, { allowEmptyArrays: 0 }); },
+            TypeError
+        );
+
+        st['throws'](
+            function () { qs.stringify({ a: [], b: 'zz' }, { allowEmptyArrays: NaN }); },
+            TypeError
+        );
+
+        st['throws'](
+            function () { qs.stringify({ a: [], b: 'zz' }, { allowEmptyArrays: null }); },
+            TypeError
+        );
+
         st.end();
     });