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// Copyright 2021 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
package config
import (
"encoding/json"
)
// Unfortunately, if we want to apply a JSON patch to some configuration, we cannot just unmarshal
// it twice - in that case json.RawMessage objects will be completely replaced, but not merged.
func MergeJSONs(left, right []byte) ([]byte, error) {
vLeft, err := parseFragment(left)
if err != nil {
return nil, err
}
vRight, err := parseFragment(right)
if err != nil {
return nil, err
}
return json.Marshal(mergeRecursive(vLeft, vRight))
}
// Recursively apply a patch to a raw JSON data.
// Patch is supposed to be a map, which possibly nests other map objects.
func PatchJSON(left []byte, patch map[string]any) ([]byte, error) {
vLeft, err := parseFragment(left)
if err != nil {
return nil, err
}
return json.Marshal(mergeRecursive(vLeft, patch))
}
func parseFragment(input []byte) (parsed any, err error) {
if len(input) == 0 {
// For convenience, we allow empty strings to be passed to the function that merges JSONs.
return
}
err = json.Unmarshal(json.RawMessage(input), &parsed)
return
}
// If one of the elements is not a map, use the new one.
// Otherwise, recursively merge map elements.
func mergeRecursive(left, right any) any {
if left == nil {
return right
}
if right == nil {
return left
}
mLeft, okLeft := left.(map[string]any)
mRight, okRight := right.(map[string]any)
if !okLeft || !okRight {
return right
}
for key, val := range mRight {
valLeft, ok := mLeft[key]
if ok {
mLeft[key] = mergeRecursive(valLeft, val)
} else {
mLeft[key] = val
}
}
return mLeft
}
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