From 980176b258942d7730607c82a6690ce38c537084 Mon Sep 17 00:00:00 2001
From: Peter Grant <petercgrant@github>
Date: Fri, 19 Feb 2016 10:51:40 -0800
Subject: [PATCH 1/3] Test cases for empty vs nil list handling

---
 list_test.go | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/list_test.go b/list_test.go
index 49c018b..c1fe07e 100644
--- a/list_test.go
+++ b/list_test.go
@@ -51,6 +51,41 @@ func TestList(t *testing.T) {
 			})
 		})
 
+		Convey("->Send(empty list)", func() {
+
+			Convey("should send a properly formatted empty List response", func() {
+
+				writer := httptest.NewRecorder()
+				err := Send(writer, req, List([]*Object{}))
+				So(err, ShouldBeNil)
+				So(writer.Code, ShouldEqual, http.StatusOK)
+
+				contentLength, convErr := strconv.Atoi(writer.HeaderMap.Get("Content-Length"))
+				So(convErr, ShouldBeNil)
+				So(contentLength, ShouldBeGreaterThan, 0)
+				So(writer.HeaderMap.Get("Content-Type"), ShouldEqual, ContentType)
+
+				req, reqErr := testRequest(writer.Body.Bytes())
+				So(reqErr, ShouldBeNil)
+
+				responseList, parseErr := ParseList(req)
+				So(parseErr, ShouldBeNil)
+				So(len(responseList), ShouldEqual, 0)
+			})
+		})
+
+		Convey("->Send(nil list)", func() {
+
+			Convey("should fail with a 500 ISE", func() {
+
+				writer := httptest.NewRecorder()
+				var list []*Object
+				err := Send(writer, req, List(list))
+				So(err, ShouldNotBeNil)
+				So(writer.Code, ShouldEqual, http.StatusInternalServerError)
+			})
+		})
+
 		Convey("->UnmarshalJSON()", func() {
 
 			Convey("should handle a data object", func() {

From f87157aecd947c2b9f8e71641bf5bc1d42603352 Mon Sep 17 00:00:00 2001
From: Peter Grant <petercgrant@github>
Date: Fri, 19 Feb 2016 10:32:33 -0800
Subject: [PATCH 2/3] Serialize empty data as empty array

---
 document.go |  6 +++---
 list.go     | 16 ++++++++++++----
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/document.go b/document.go
index fbaa21f..642a451 100644
--- a/document.go
+++ b/document.go
@@ -12,7 +12,7 @@ Refer to the JSON API Specification for a full descriptor
 of each attribute: http://jsonapi.org/format/#document-structure
 */
 type Document struct {
-	Data     List        `json:"data,omitempty"`
+	Data     List        `json:"data"`
 	Errors   ErrorList   `json:"errors,omitempty"`
 	Links    *Link       `json:"links,omitempty"`
 	Included []*Object   `json:"included,omitempty"`
@@ -89,10 +89,10 @@ func (d *Document) Validate(r *http.Request, response bool) *Error {
 		return nil
 	}
 
-	if !d.HasErrors() && !d.HasData() {
+	if !d.HasErrors() && d.Data == nil {
 		return ISE("Both `errors` and `data` cannot be blank for a JSON response")
 	}
-	if d.HasErrors() && d.HasData() {
+	if d.HasErrors() && d.Data != nil {
 		return ISE("Both `errors` and `data` cannot be set for a JSON response")
 	}
 	if !d.HasData() && d.Included != nil {
diff --git a/list.go b/list.go
index 2070ba4..4938d57 100644
--- a/list.go
+++ b/list.go
@@ -55,15 +55,23 @@ func (list *List) UnmarshalJSON(rawData []byte) error {
 MarshalJSON returns a top level object for the "data" attribute if a single object. In
 all other cases returns a JSON encoded list for "data".
 */
-func (list List) MarshalJSON() ([]byte, error) {
+func (list *List) MarshalJSON() ([]byte, error) {
 	// avoid stack overflow by using this subtype for marshaling
 	type MarshalList List
-	marshalList := MarshalList(list)
-	count := len(marshalList)
+	marshalList := (*MarshalList)(list)
+	isnil := marshalList == nil
+	count := 0
+	if !isnil {
+		count = len(*marshalList)
+	}
 
 	switch {
+	case isnil:
+		return nil, nil
+	case count == 0:
+		return []byte("[]"), nil
 	case count == 1:
-		return json.Marshal(marshalList[0])
+		return json.Marshal((*marshalList)[0])
 	default:
 		return json.Marshal(marshalList)
 	}

From 25be454751bd62cd7f6d4369b605e6164cd23bae Mon Sep 17 00:00:00 2001
From: Peter Grant <petercgrant@github>
Date: Mon, 22 Feb 2016 11:29:03 -0800
Subject: [PATCH 3/3] Address code review comments

---
 list.go | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/list.go b/list.go
index 4938d57..3d72bea 100644
--- a/list.go
+++ b/list.go
@@ -53,25 +53,25 @@ func (list *List) UnmarshalJSON(rawData []byte) error {
 
 /*
 MarshalJSON returns a top level object for the "data" attribute if a single object. In
-all other cases returns a JSON encoded list for "data".
+all other cases returns a JSON encoded list for "data". We use a pointer receiver here
+so we are able to distinguish between nil (don't serialize) and empty (serialize as []).
 */
 func (list *List) MarshalJSON() ([]byte, error) {
 	// avoid stack overflow by using this subtype for marshaling
 	type MarshalList List
-	marshalList := (*MarshalList)(list)
-	isnil := marshalList == nil
-	count := 0
-	if !isnil {
-		count = len(*marshalList)
+
+	if list == nil {
+		return nil, nil
 	}
 
+	marshalList := MarshalList(*list)
+	count := len(marshalList)
+
 	switch {
-	case isnil:
-		return nil, nil
 	case count == 0:
 		return []byte("[]"), nil
 	case count == 1:
-		return json.Marshal((*marshalList)[0])
+		return json.Marshal(marshalList[0])
 	default:
 		return json.Marshal(marshalList)
 	}