feat(influxd): Add errors.List to simplify capturing a list of errors

kit/errors/list.go

@@ -0,0 +1,59 @@
+package errors
+
+import (
+	"errors"
+	"strings"
+)
+
+// List represents a list of errors.
+type List struct {
+	errs []error
+	err  error // cached error
+}
+
+// Append adds err to the errors list.
+func (l *List) Append(err error) {
+	l.errs = append(l.errs, err)
+	l.err = nil
+}
+
+// AppendString adds a new error that formats as the given text.
+func (l *List) AppendString(text string) {
+	l.errs = append(l.errs, errors.New(text))
+	l.err = nil
+}
+
+// Clear removes all the previously appended errors from the list.
+func (l *List) Clear() {
+	for i := range l.errs {
+		l.errs[i] = nil
+	}
+	l.errs = l.errs[:0]
+	l.err = nil
+}
+
+// Err returns an error composed of the list of errors, separated by a new line, or nil if no errors
+// were appended.
+func (l *List) Err() error {
+	if len(l.errs) == 0 {
+		return nil
+	}
+
+	if l.err != nil {
+		switch len(l.errs) {
+		case 1:
+			l.err = l.errs[0]
+
+		default:
+			var sb strings.Builder
+			sb.WriteString(l.errs[0].Error())
+			for _, err := range l.errs[1:] {
+				sb.WriteRune('\n')
+				sb.WriteString(err.Error())
+			}
+			l.err = errors.New(sb.String())
+		}
+	}
+
+	return l.err
+}