Skip nil data from serialized JSON

README.md

@@ -22,7 +22,9 @@ For a better understanding of the features provided by the package check the doc
 
 # Quick demo
 
-There's an example at `examples/example1/example1.go` that shows how to use the package. Here's the code for the example:
+There's an example at `examples/example1/example1.go` that shows how to use the package.
+
+<details><summary>Here's the code for the example:</summary>
 
 ```go
 package main
@@ -78,11 +80,11 @@ func open() error {
 func main() {
 	if err := createTransaction("tx_123456"); err != nil {
 		b, _ := json.MarshalIndent(err, "", "  ")
-		fmt.Println("Error logged as a JSON structure using the JSON.MarshalIndent:")
+		fmt.Println("Error logged as a JSON structure using the json.MarshalIndent:")
 		fmt.Printf("%s\n", b)
 
 		b, _ = json.Marshal(err)
-		fmt.Println("\nError logged as a JSON structure using the JSON.Marshal:")
+		fmt.Println("\nError logged as a JSON structure using the json.Marshal:")
 		fmt.Printf("%s\n", b)
 
 		fmt.Println("\nError logged using the s format specifier:")
@@ -94,11 +96,13 @@ func main() {
 }
 ```
 
-Here's the execution of the example:
+</details>
+
+<details><summary>Here's the execution of the example:</summary>
 
 ```
-$ go run examples/example1/example1.go 
-Error logged as a JSON structure using the JSON.MarshalIndent:
+$ go run examples/example1/example1.go
+Error logged as a JSON structure using the json.MarshalIndent:
 [
   {
     "data": {
@@ -160,7 +164,7 @@ Error logged as a JSON structure using the JSON.MarshalIndent:
   }
 ]
 
-Error logged as a JSON structure using the JSON.Marshal:
+Error logged as a JSON structure using the json.Marshal:
 [{"data":{"transactionId":"tx_123456","userId":"67890"},"message":"failed to complete the transaction on bank_123456","stack":["main.createTransaction @ /root/hack/errors/examples/example1/example1.go:13","main.main @ /root/hack/errors/examples/example1/example1.go:52","runtime/internal/atomic.(*Uint32).Load @ /root/go/version/go1.21.0/src/runtime/internal/atomic/types.go:194","runtime.goexit @ /root/go/version/go1.21.0/src/runtime/asm_amd64.s:1651"]},{"data":{"operation":"update","tableName":"transactions"},"message":"failed to update the database","stack":["main.updateDatabase @ /root/hack/errors/examples/example1/example1.go:24","main.createTransaction @ /root/hack/errors/examples/example1/example1.go:12","main.main @ /root/hack/errors/examples/example1/example1.go:52","runtime/internal/atomic.(*Uint32).Load @ /root/go/version/go1.21.0/src/runtime/internal/atomic/types.go:194","runtime.goexit @ /root/go/version/go1.21.0/src/runtime/asm_amd64.s:1651"]},{"data":{"server":"db-server-01","timeoutSeconds":30},"message":"connection timeout","stack":["main.createConnection @ /root/hack/errors/examples/example1/example1.go:35","main.updateDatabase @ /root/hack/errors/examples/example1/example1.go:23","main.createTransaction @ /root/hack/errors/examples/example1/example1.go:12","main.main @ /root/hack/errors/examples/example1/example1.go:52","runtime/internal/atomic.(*Uint32).Load @ /root/go/version/go1.21.0/src/runtime/internal/atomic/types.go:194","runtime.goexit @ /root/go/version/go1.21.0/src/runtime/asm_amd64.s:1651"]},{"data":{"network":"internal","severity":"high"},"message":"network instability detected","stack":["main.open @ /root/hack/errors/examples/example1/example1.go:45","main.createConnection @ /root/hack/errors/examples/example1/example1.go:34","main.updateDatabase @ /root/hack/errors/examples/example1/example1.go:23","main.createTransaction @ /root/hack/errors/examples/example1/example1.go:12","main.main @ /root/hack/errors/examples/example1/example1.go:52","runtime/internal/atomic.(*Uint32).Load @ /root/go/version/go1.21.0/src/runtime/internal/atomic/types.go:194","runtime.goexit @ /root/go/version/go1.21.0/src/runtime/asm_amd64.s:1651"]}]
 
 Error logged using the s format specifier:
@@ -170,8 +174,8 @@ Error logged using the +v format specifier:
 message:
         "failed to complete the transaction on bank_123456"
 data:
-        transactionId: tx_123456
         userId: 67890
+        transactionId: tx_123456
 stack:
         main.createTransaction @ /root/hack/errors/examples/example1/example1.go:13
         main.main @ /root/hack/errors/examples/example1/example1.go:52
@@ -216,4 +220,6 @@ cause:
                                 main.main @ /root/hack/errors/examples/example1/example1.go:52
                                 runtime/internal/atomic.(*Uint32).Load @ /root/go/version/go1.21.0/src/runtime/internal/atomic/types.go:194
                                 runtime.goexit @ /root/go/version/go1.21.0/src/runtime/asm_amd64.s:1651
-```
+```
+
+</details>

convertion.go

@@ -30,7 +30,9 @@ func toMapAndCause(err error) (map[string]any, error) {
 
 	if e, ok := err.(*Err); ok {
 		errMap["message"] = e.Message
-		errMap["data"] = e.Data
+		if e.Data != nil {
+			errMap["data"] = e.Data
+		}
 		errMap["stack"] = e.Stack
 		errCause = e.Cause
 	} else {

error_test.go

@@ -10,7 +10,9 @@ func TestJSONMarshaling(t *testing.T) {
 	t.Run("when marshaling a nested chain of errors.Err errors, should marshal the full chain", func(t *testing.T) {
 		err1 := New("context timeout")
 		err2 := Wrap(err1, "failed to connect to the database")
-		err3 := Wrap(err2, "failed to start the server")
+		err3 := Wrapd(err2, Data{
+			"server": "db-server-01",
+		}, "failed to start the server")
 
 		b, err := json.MarshalIndent(err3, "", "  ")
 		if err != nil {
@@ -27,17 +29,45 @@ func TestJSONMarshaling(t *testing.T) {
 			t.Fatalf("unexpected number of errors, got %d, expected %d", len(errs), 3)
 		}
 
+		// testing err3
+
 		if fmt.Sprint(errs[0]["message"]) != err3.(*Err).Message {
 			t.Errorf("unexpected error message, got %q, expected %q", errs[0]["message"], err3.(*Err).Message)
 		}
 
+		dataErr3, ok := errs[0]["data"]
+		if !ok {
+			t.Errorf("unexpected data, got undefined key, expected %v", err3.(*Err).Data)
+		}
+
+		b1, err := json.Marshal(dataErr3)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		b2, err := json.Marshal(err3.(*Err).Data)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+
+		if string(b1) != string(b2) {
+			t.Errorf("unexpected data, got %s, expected %s", b1, b2)
+		}
+
+		// testing err2
+
 		if fmt.Sprint(errs[1]["message"]) != err2.(*Err).Message {
 			t.Errorf("unexpected error message, got %q, expected %q", errs[1]["message"], err2.(*Err).Message)
 		}
 
+		// testing err1
+
 		if fmt.Sprint(errs[2]["message"]) != err1.(*Err).Message {
 			t.Errorf("unexpected error message, got %q, expected %q", errs[2]["message"], err1.(*Err).Message)
 		}
+
+		if _, ok := errs[2]["data"]; ok {
+			t.Errorf("unexpected data, got %v, expected undefined key", errs[0]["data"])
+		}
 	})
 
 	t.Run("when marshaling a chain of errors.Err and standard errors, should marshal the full chain", func(t *testing.T) {

examples/example1/example1.go

@@ -51,11 +51,11 @@ func open() error {
 func main() {
 	if err := createTransaction("tx_123456"); err != nil {
 		b, _ := json.MarshalIndent(err, "", "  ")
-		fmt.Println("Error logged as a JSON structure using the JSON.MarshalIndent:")
+		fmt.Println("Error logged as a JSON structure using the json.MarshalIndent:")
 		fmt.Printf("%s\n", b)
 
 		b, _ = json.Marshal(err)
-		fmt.Println("\nError logged as a JSON structure using the JSON.Marshal:")
+		fmt.Println("\nError logged as a JSON structure using the json.Marshal:")
 		fmt.Printf("%s\n", b)
 
 		fmt.Println("\nError logged using the s format specifier:")