implement json.Umarshaler and json.Unmarshaler on datasetore.Key

key.go

 package datastore
 
 import (
+	"errors"
 	"path"
 	"strings"
 
@@ -232,6 +233,23 @@ func (k Key) IsTopLevel() bool {
 	return len(k.List()) == 1
 }
 
+// MarshalJSON implements the json.Marshaler interface,
+// keys are represented as JSON strings
+func (k Key) MarshalJSON() ([]byte, error) {
+	return []byte(`"` + k.String() + `"`), nil
+}
+
+// MarshalJSON implements the json.Unmarshaler interface,
+// keys will parse any value specified as a key to a string
+func (k *Key) UnmarshalJSON(data []byte) error {
+	if len(data) < 2 {
+		k.Clean()
+		return errors.New("too short to unmarshal key to json string")
+	}
+	*k = NewKey(string(data[1 : len(data)-1]))
+	return nil
+}
+
 // RandomKey returns a randomly (uuid) generated key.
 //   RandomKey()
 //   NewKey("/f98719ea086343f7b71f32ea9d9d521d")

key_test.go

@@ -155,3 +155,48 @@ func (ks *KeySuite) TestLess(c *C) {
 	checkLess("/a/b/c/d/e/f/g/h", "/b")
 	checkLess("/", "/a")
 }
+
+func TestKeyMarshalJSON(t *testing.T) {
+	cases := []struct {
+		key  Key
+		data []byte
+		err  string
+	}{
+		{NewKey("/a/b/c"), []byte("\"/a/b/c\""), ""},
+	}
+
+	for i, c := range cases {
+		out, err := c.key.MarshalJSON()
+		if !(err == nil && c.err == "" || err != nil && err.Error() == c.err) {
+			t.Errorf("case %d marshal error mismatch: expected: %s, got: %s", i, c.err, err)
+		}
+		if !bytes.Equal(c.data, out) {
+			t.Errorf("case %d value mismatch: expected: %s, got: %s", i, string(c.data), string(out))
+		}
+	}
+}
+
+func TestKeyUnmarshalJSON(t *testing.T) {
+	cases := []struct {
+		data []byte
+		key  Key
+		err  string
+	}{
+		{[]byte("\"/a/b/c\""), NewKey("/a/b/c"), ""},
+		{[]byte{}, NewKey("/"), "too short to unmarshal json string"},
+		{[]byte{'"'}, NewKey("/"), "too short to unmarshal json string"},
+		{[]byte(`""`), NewKey("/"), ""},
+	}
+
+	for i, c := range cases {
+		key := Key{}
+		err := key.UnmarshalJSON(c.data)
+		if !(err == nil && c.err == "" || err != nil && err.Error() == c.err) {
+			t.Errorf("case %d marshal error mismatch: expected: %s, got: %s", i, c.err, err)
+		}
+
+		if !key.Equal(c.key) {
+			t.Errorf("case %d key mismatch: expected: %s, got: %s", i, c.key, key)
+		}
+	}
+}