refactor: simplify BatchError (#4292)

core/errorx/batcherror.go

@@ -5,17 +5,13 @@ import (
 	"sync"
 )
 
-type (
-	// A BatchError is an error that can hold multiple errors.
-	BatchError struct {
-		errs errorArray
-		lock sync.Mutex
-	}
+// BatchError is an error that can hold multiple errors.
+type BatchError struct {
+	errs []error
+	lock sync.RWMutex
+}
 
-	errorArray []error
-)
-
-// Add adds errs to be, nil errors are ignored.
+// Add adds one or more non-nil errors to the BatchError instance.
 func (be *BatchError) Add(errs ...error) {
 	be.lock.Lock()
 	defer be.lock.Unlock()
@@ -27,35 +23,20 @@ func (be *BatchError) Add(errs ...error) {
 	}
 }
 
-// Err returns an error that represents all errors.
+// Err returns an error that represents all accumulated errors.
+// It returns nil if there are no errors.
 func (be *BatchError) Err() error {
-	be.lock.Lock()
-	defer be.lock.Unlock()
+	be.lock.RLock()
+	defer be.lock.RUnlock()
 
-	switch len(be.errs) {
-	case 0:
-		return nil
-	case 1:
-		return be.errs[0]
-	default:
-		return be.errs
-	}
+	// If there are no non-nil errors, errors.Join(...) returns nil.
+	return errors.Join(be.errs...)
 }
 
-// NotNil checks if any error inside.
+// NotNil checks if there is at least one error inside the BatchError.
 func (be *BatchError) NotNil() bool {
-	be.lock.Lock()
-	defer be.lock.Unlock()
+	be.lock.RLock()
+	defer be.lock.RUnlock()
 
 	return len(be.errs) > 0
 }
-
-// Error returns a string that represents inside errors.
-func (ea errorArray) Error() string {
-	return errors.Join(ea...).Error()
-}
-
-// Unwrap combine the errors in the errorArray into a single error return
-func (ea errorArray) Unwrap() error {
-	return errors.Join(ea...)
-}