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proposal: encoding/json: mark field when struct decoding #54351

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Ccheers opened this issue Aug 9, 2022 · 1 comment
Closed

proposal: encoding/json: mark field when struct decoding #54351

Ccheers opened this issue Aug 9, 2022 · 1 comment
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@Ccheers
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Ccheers commented Aug 9, 2022

in this case the id field value is 5 , but the key "id" is match in better.

package main

import (
	"encoding/json"
	"log"
)

type Foo struct {
	ID uint `json:"id"`
}

const jsonStr = `{"id":2,"ID":5}`

func main() {
	a := &Foo{}
	b := make(map[string]interface{})
	json.Unmarshal([]byte(jsonStr), a)
	json.Unmarshal([]byte(jsonStr), &b)

	log.Println(a)
	// output &{5}

	log.Println(b)
	// output map[ID:5 id:2]
}

add a flag like "isMatched" when matched with nameIndex set the flag "true"

like this:

type structFields struct {
	list      []field
	nameIndex map[string]int
}

// A field represents a single field found in a struct.
type field struct {
	...

        isMatched bool // add a flag when nameIndex matched
}

https://github.com/golang/go/blob/master/src/encoding/json/decode.go#L702

	if i, ok := fields.nameIndex[string(key)]; ok {
		// Found an exact name match.
		f = &fields.list[i]
+               f.isMatched = true
	} else {
		// Fall back to the expensive case-insensitive
		// linear search.
		for i := range fields.list {
			ff := &fields.list[i]
+			if !ff.isMatched && ff.equalFold(ff.nameBytes, key) {
				f = ff
				break
			}
		}
	}
@gopherbot gopherbot added this to the Proposal milestone Aug 9, 2022
@seankhliao
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Duplicate of #14750

@seankhliao seankhliao marked this as a duplicate of #14750 Aug 9, 2022
@seankhliao seankhliao closed this as not planned Won't fix, can't repro, duplicate, stale Aug 9, 2022
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