json: use reflect.IsZero on arrays instead of len check

Author: as

LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

@@ -0,0 +1,20 @@
+# json
+A fork of encoding/json that fixes omitempty behavior on structs
+
+https://play.golang.org/p/M8AOBJgWMJy
+
+# Example
+```
+T := struct {
+	B struct {} `json:",omitempty"`
+}{}
+
+json.NewEncoder(os.Stdout).Encode(T) // stdlib
+NewEncoder(os.Stdout).Encode(T) // this package
+```
+
+# Output
+```
+{"B":{}} // stdlib
+{} // this package
+```

encode.go

@@ -338,9 +338,9 @@ func (e *encodeState) error(err error) {
 
 func isEmptyValue(v reflect.Value) bool {
 	switch v.Kind() {
-	case reflect.Struct:
+	case reflect.Struct, reflect.Array:
 		return v.IsZero()
-	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+	case reflect.Map, reflect.Slice, reflect.String:
 		return v.Len() == 0
 	case reflect.Bool:
 		return !v.Bool()