92 lines
2.2 KiB
Go
92 lines
2.2 KiB
Go
package merge
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import (
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"reflect"
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"github.com/imdario/mergo"
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"github.com/pkg/errors"
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)
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var (
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ErrNonPointerDst = errors.New("dst is not a pointer")
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ErrUnsupportedMerge = errors.New("unsupported merge")
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ErrUnexpectedFailedCast = errors.New("unexpected failed cast")
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)
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func Merge(dst interface{}, sources ...interface{}) error {
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if reflect.TypeOf(dst).Kind() != reflect.Ptr {
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return errors.WithStack(ErrNonPointerDst)
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}
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dstPointedKind := reflect.Indirect(reflect.ValueOf(dst)).Elem().Kind()
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for _, src := range sources {
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srcKind := reflect.ValueOf(src).Kind()
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switch dstPointedKind {
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case reflect.Map:
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if srcKind != dstPointedKind {
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return errors.WithStack(unsupportedMergeError(dstPointedKind, srcKind))
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}
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if err := mergeMaps(dst, src); err != nil {
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return errors.WithStack(err)
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}
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case reflect.Slice:
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if srcKind != dstPointedKind {
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return errors.WithStack(unsupportedMergeError(dstPointedKind, srcKind))
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}
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if err := mergeSlices(dst, src); err != nil {
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return errors.WithStack(err)
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}
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default:
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return errors.WithStack(unsupportedMergeError(dstPointedKind, srcKind))
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}
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}
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return nil
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}
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func unsupportedMergeError(dstKind reflect.Kind, defaultsKind reflect.Kind) error {
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return errors.Wrapf(ErrUnsupportedMerge, "could not merge '%s' with defaults '%s'", dstKind, defaultsKind)
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}
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func mergeMaps(dst interface{}, defaults interface{}) error {
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dstMap, ok := reflect.Indirect(reflect.ValueOf(dst)).Elem().Interface().(map[string]interface{})
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if !ok {
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return errors.WithStack(ErrUnexpectedFailedCast)
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}
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defaultsMap, ok := defaults.(map[string]interface{})
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if !ok {
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return errors.WithStack(ErrUnexpectedFailedCast)
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}
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if err := mergo.Merge(&dstMap, defaultsMap, mergo.WithOverride); err != nil {
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return errors.WithStack(err)
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}
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return nil
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}
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func mergeSlices(dst interface{}, defaults interface{}) error {
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dstSlice, ok := reflect.Indirect(reflect.ValueOf(dst)).Elem().Interface().([]interface{})
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if !ok {
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return errors.WithStack(ErrUnexpectedFailedCast)
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}
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defaultsSlice, ok := defaults.([]interface{})
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if !ok {
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return errors.WithStack(ErrUnexpectedFailedCast)
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}
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if err := mergo.Merge(&dstSlice, defaultsSlice, mergo.WithOverride); err != nil {
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return errors.WithStack(err)
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}
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return nil
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}
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