restructured the project to comply community guideline, for others check release note

internal/error/builder.go

@@ -0,0 +1,70 @@
+package error
+
+import (
+	"fmt"
+	"sync"
+)
+
+type Builder struct {
+	*builder
+}
+
+type builder struct {
+	message string
+	errors  []NestedError
+	sync.Mutex
+}
+
+func NewBuilder(format string, args ...any) Builder {
+	return Builder{&builder{message: fmt.Sprintf(format, args...)}}
+}
+
+// adding nil / nil is no-op,
+// you may safely pass expressions returning error to it
+func (b Builder) Add(err NestedError) Builder {
+	if err != nil {
+		b.Lock()
+		// TODO: if err severity is higher than b.severity, update b.severity
+		b.errors = append(b.errors, err)
+		b.Unlock()
+	}
+	return b
+}
+
+func (b Builder) AddE(err error) Builder {
+	return b.Add(From(err))
+}
+
+func (b Builder) Addf(format string, args ...any) Builder {
+	return b.Add(errorf(format, args...))
+}
+
+// Build builds a NestedError based on the errors collected in the Builder.
+//
+// If there are no errors in the Builder, it returns a Nil() NestedError.
+// Otherwise, it returns a NestedError with the message and the errors collected.
+//
+// Returns:
+//   - NestedError: the built NestedError.
+func (b Builder) Build() NestedError {
+	if len(b.errors) == 0 {
+		return nil
+	} else if len(b.errors) == 1 {
+		return b.errors[0]
+	}
+	return Join(b.message, b.errors...)
+}
+
+func (b Builder) To(ptr *NestedError) {
+	if ptr == nil {
+		return
+	} else if *ptr == nil {
+		*ptr = b.Build()
+	} else {
+		(*ptr).With(b.Build())
+	}
+}
+
+func (b Builder) HasError() bool {
+	return len(b.errors) > 0
+}