Fix errors serialization

.gitignore

@@ -22,3 +22,5 @@ _testmain.go
 *.exe
 *.test
 *.prof
+
+cover.*

Makefile

@@ -1,2 +1,3 @@
 tests:
-	go test -v ./...
+	go test -v -coverprofile=cover.out ./...
+	go tool cover -html=cover.out -o=cover.html

README.md

@@ -97,69 +97,71 @@ func main() {
 Here's the execution of the example:
 
 ```
-$ go run examples/example1/example1.go
+$ go run examples/example1/example1.go 
 Error logged as a JSON structure using the JSON.MarshalIndent:
-{
-  "message": "failed to complete the transaction on bank_123456",
-  "data": {
-    "transactionId": "tx_123456",
-    "userId": "67890"
+[
+  {
+    "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"
+    ]
   },
-  "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"
-  ],
-  "cause": {
-    "message": "failed to update the database",
+  {
     "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"
-    ],
-    "cause": {
-      "message": "connection timeout",
-      "data": {
-        "server": "db-server-01",
-        "timeoutSeconds": 30
-      },
-      "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"
-      ],
-      "cause": {
-        "message": "network instability detected",
-        "data": {
-          "network": "internal",
-          "severity": "high"
-        },
-        "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"
-        ]
-      }
-    }
+    ]
+  },
+  {
+    "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 as a JSON structure using the JSON.Marshal:
-{"message":"failed to complete the transaction on bank_123456","data":{"transactionId":"tx_123456","userId":"67890"},"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"],"cause":{"message":"failed to update the database","data":{"operation":"update","tableName":"transactions"},"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"],"cause":{"message":"connection timeout","data":{"server":"db-server-01","timeoutSeconds":30},"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"],"cause":{"message":"network instability detected","data":{"network":"internal","severity":"high"},"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"]}}}}
+[{"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:
 failed to complete the transaction on bank_123456: failed to update the database: connection timeout: network instability detected
@@ -204,8 +206,8 @@ cause:
                         message:
                                 "network instability detected"
                         data:
-                                network: internal
                                 severity: high
+                                network: internal
                         stack:
                                 main.open @ /root/hack/errors/examples/example1/example1.go:45
                                 main.createConnection @ /root/hack/errors/examples/example1/example1.go:34

convertion.go

@@ -0,0 +1,42 @@
+package errors
+
+import "errors"
+
+// toMapsSlice converts an error and its causes to flat slice of maps where each map represents an error.
+func toMapsSlice(err error) []map[string]any {
+	errMaps := make([]map[string]any, 0)
+
+	if err == nil {
+		return errMaps
+	}
+
+	currentErr := err
+	for {
+		errMap, errCause := toMapAndCause(currentErr)
+		errMaps = append(errMaps, errMap)
+		if errCause == nil {
+			break
+		}
+		currentErr = errCause
+	}
+
+	return errMaps
+}
+
+// toMapAndCause converts an error to a map and extracts the cause.
+func toMapAndCause(err error) (map[string]any, error) {
+	errMap := make(map[string]any)
+	var errCause error
+
+	if e, ok := err.(*Err); ok {
+		errMap["message"] = e.Message
+		errMap["data"] = e.Data
+		errMap["stack"] = e.Stack
+		errCause = e.Cause
+	} else {
+		errMap["message"] = err.Error()
+		errCause = errors.Unwrap(err)
+	}
+
+	return errMap, errCause
+}

error.go

@@ -1,6 +1,9 @@
 package errors
 
-import "fmt"
+import (
+	"encoding/json"
+	"fmt"
+)
 
 // Err is the error struct used internally by the package. This type should only be used for type assertions.
 type Err struct {
@@ -31,28 +34,6 @@ func (e Err) Unwrap() error {
 	return e.Cause
 }
 
-// WithStack adds a stack trace to the provided error if it is an Err or *Err.
-func WithStack(err error) error {
-	if e, ok := err.(Err); ok {
-		e.Stack = callers()
-		return e
-	} else if e, ok := err.(*Err); ok {
-		e.Stack = callers()
-		return e
-	} else {
-		return err
-	}
-}
-
-// WithCause adds a cause to the provided error if it is an Err or *Err.
-func WithCause(err error, cause error) error {
-	if e, ok := err.(Err); ok {
-		e.Cause = cause
-		return e
-	} else if e, ok := err.(*Err); ok {
-		e.Cause = cause
-		return e
-	} else {
-		return err
-	}
+func (e *Err) MarshalJSON() ([]byte, error) {
+	return json.Marshal(toMapsSlice(e))
 }

error_test.go

@@ -0,0 +1,75 @@
+package errors
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+)
+
+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")
+
+		b, err := json.MarshalIndent(err3, "", "  ")
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+
+		var errs []map[string]any
+		err = json.Unmarshal(b, &errs)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+
+		if len(errs) != 3 {
+			t.Fatalf("unexpected number of errors, got %d, expected %d", len(errs), 3)
+		}
+
+		if fmt.Sprint(errs[0]["message"]) != err3.(*Err).Message {
+			t.Errorf("unexpected error message, got %q, expected %q", errs[0]["message"], err3.(*Err).Message)
+		}
+
+		if fmt.Sprint(errs[1]["message"]) != err2.(*Err).Message {
+			t.Errorf("unexpected error message, got %q, expected %q", errs[1]["message"], err2.(*Err).Message)
+		}
+
+		if fmt.Sprint(errs[2]["message"]) != err1.(*Err).Message {
+			t.Errorf("unexpected error message, got %q, expected %q", errs[2]["message"], err1.(*Err).Message)
+		}
+	})
+
+	t.Run("when marshaling a chain of errors.Err and standard errors, should marshal the full chain", func(t *testing.T) {
+		err1 := New("context timeout")
+		err2 := fmt.Errorf("failed to connect to the database: %w", err1)
+		err3 := Wrap(err2, "failed to start the server")
+
+		b, err := json.MarshalIndent(err3, "", "  ")
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+
+		var errs []map[string]any
+		err = json.Unmarshal(b, &errs)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+
+		if len(errs) != 3 {
+			t.Fatalf("unexpected number of errors, got %d, expected %d", len(errs), 3)
+		}
+
+		if fmt.Sprint(errs[0]["message"]) != err3.(*Err).Message {
+			t.Errorf("unexpected error message, got %q, expected %q", errs[0]["message"], err3.(*Err).Message)
+		}
+
+		if fmt.Sprint(errs[1]["message"]) != err2.Error() {
+			t.Errorf("unexpected error message, got %q, expected %q", errs[1]["message"], err2.Error())
+		}
+
+		if fmt.Sprint(errs[2]["message"]) != err1.(*Err).Message {
+			t.Errorf("unexpected error message, got %q, expected %q", errs[2]["message"], err1.(*Err).Message)
+		}
+	})
+}

errors.go

@@ -75,3 +75,29 @@ func Wrapdf(err error, data Data, format string, args ...any) error {
 		Cause:   err,
 	}
 }
+
+// WithStack adds a stack trace to the provided error if it is an Err or *Err.
+func WithStack(err error) error {
+	if e, ok := err.(Err); ok {
+		e.Stack = callers()
+		return e
+	} else if e, ok := err.(*Err); ok {
+		e.Stack = callers()
+		return e
+	} else {
+		return err
+	}
+}
+
+// WithCause adds a cause to the provided error if it is an Err or *Err.
+func WithCause(err error, cause error) error {
+	if e, ok := err.(Err); ok {
+		e.Cause = cause
+		return e
+	} else if e, ok := err.(*Err); ok {
+		e.Cause = cause
+		return e
+	} else {
+		return err
+	}
+}