Ensure that JSON.GET returns Nil response

Updated JSONCmd.readReply to return redis.Nil if no results.
Added a doc line for Val() and Expanded() methods of JSONCmd.
Added a test case for non existent keys in json_test.go.

Original-PR: #2987

Author: nic-gibson

json.go

@@ -114,9 +114,14 @@ func (cmd *JSONCmd) Expanded() (interface{}, error) {
 }
 
 func (cmd *JSONCmd) readReply(rd *proto.Reader) error {
+	// nil response from JSON.(M)GET (cmd.baseCmd.err will be "redis: nil")
+	if cmd.baseCmd.Err() == Nil {
+		cmd.val = ""
+		return Nil
+	}
 
+	// Handle other base command errors
 	if cmd.baseCmd.Err() != nil {
-		cmd.val = ""
 		return cmd.baseCmd.Err()
 	}
 
@@ -128,7 +133,10 @@ func (cmd *JSONCmd) readReply(rd *proto.Reader) error {
 		if err != nil {
 			return err
 		}
+
+		// Empty array could indicate no results found for JSON path
 		if size == 0 {
+			cmd.val = ""
 			return Nil
 		}
 

json_test.go

@@ -263,10 +263,6 @@ var _ = Describe("JSON Commands", Label("json"), func() {
 				Expect(err).NotTo(HaveOccurred())
 				Expect(res).To(Equal("OK"))
 
-				_, err = client.JSONGet(ctx, "this-key-does-not-exist", "$").Result()
-				Expect(err).To(HaveOccurred())
-				Expect(err).To(BeIdenticalTo(redis.Nil))
-
 				resArr, err := client.JSONArrIndex(ctx, "doc1", "$.store.book[?(@.price<10)].size", 20).Result()
 				Expect(err).NotTo(HaveOccurred())
 				Expect(resArr).To(Equal([]int64{1, 2}))
@@ -681,6 +677,54 @@ var _ = Describe("JSON Commands", Label("json"), func() {
 				Expect(cmd2.Val()[0]).To(Or(Equal([]interface{}{"boolean"}), Equal("boolean")))
 			})
 		})
+
+		Describe("JSON Nil Handling", func() {
+			It("should return redis.Nil for non-existent key", func() {
+				_, err := client.JSONGet(ctx, "non-existent-key", "$").Result()
+				Expect(err).To(Equal(redis.Nil))
+			})
+
+			It("should return redis.Nil for non-existent path in existing key", func() {
+				err := client.JSONSet(ctx, "test-key", "$", `{"a": 1, "b": "hello"}`).Err()
+				Expect(err).NotTo(HaveOccurred())
+
+				_, err = client.JSONGet(ctx, "test-key", "$.nonexistent").Result()
+				Expect(err).To(Equal(redis.Nil))
+			})
+
+			It("should distinguish empty array from nil", func() {
+				err := client.JSONSet(ctx, "test-key", "$", `{"arr": [], "obj": {}}`).Err()
+				Expect(err).NotTo(HaveOccurred())
+
+				// Empty array should return the array, not nil
+				val, err := client.JSONGet(ctx, "test-key", "$.arr").Result()
+				Expect(err).NotTo(HaveOccurred())
+				Expect(val).To(Equal("[[]]"))
+
+				// Non-existent field should return nil
+				_, err = client.JSONGet(ctx, "test-key", "$.missing").Result()
+				Expect(err).To(Equal(redis.Nil))
+			})
+
+			It("should handle multiple paths with mixed results", func() {
+				err := client.JSONSet(ctx, "test-key", "$", `{"a": 1, "b": 2}`).Err()
+				Expect(err).NotTo(HaveOccurred())
+
+				// Path that exists
+				val, err := client.JSONGet(ctx, "test-key", "$.a").Result()
+				Expect(err).NotTo(HaveOccurred())
+				Expect(val).To(Equal("[1]"))
+
+				// Path that doesn't exist
+				_, err = client.JSONGet(ctx, "test-key", "$.c").Result()
+				Expect(err).To(Equal(redis.Nil))
+			})
+
+			AfterEach(func() {
+				// Clean up test keys
+				client.Del(ctx, "test-key", "non-existent-key")
+			})
+		})
 	}
 })