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encoding/json: json.Marshal() doesn't produce right result #61062

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DiJester opened this issue Jun 29, 2023 · 3 comments
Closed

encoding/json: json.Marshal() doesn't produce right result #61062

DiJester opened this issue Jun 29, 2023 · 3 comments
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@DiJester
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DiJester commented Jun 29, 2023 •
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What version of Go are you using (go version)?

$ go version
go version go1.19.3 darwin/amd64

Does this issue reproduce with the latest release?

Not test yet

What operating system and processor architecture are you using (go env)?

MacOS

go env Output
$ go env

What did you do?

I run the code below

func main() {
	data := []byte{110, 117, 108, 108}

	list := []string{}

	err := json.Unmarshal(data, &list)
	if err != nil {
		fmt.Println(err)
	}

	if len(list) == 0 {

		fmt.Printf("list is: %+v \n\r", list)
		listData, err := json.Marshal(list)
		if err != nil {
			fmt.Println(err)
		}
		fmt.Printf("list marshalled bytes are: %+v \n\r", listData)

	}

}

Why the unmarshalled listData is 
[110 117 108 108] , but not [91, 93]

What did you expect to see?

The marshlled bytes for list should be [91, 93]

What did you see instead?

The marshlled bytes for list is [110 117 108 108]
@Jorropo
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Jorropo commented Jun 29, 2023 •
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110 117 108 108 is literally the string null.
You are parsing null into a []string which gives you []string(nil), you are then serializing the []string(nil) you just got to the json object: null.

Everything in your example works like expected.

@bcmills
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bcmills commented Jun 29, 2023

This seems to be working as documented (https://pkg.go.dev/encoding/json#Marshal):

Array and slice values encode as JSON arrays, except that … a nil slice encodes as the null JSON value.

@bcmills bcmills closed this as not planned Won't fix, can't repro, duplicate, stale Jun 29, 2023
@DiJester
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This seems to be working as documented (https://pkg.go.dev/encoding/json#Marshal):

Array and slice values encode as JSON arrays, except that … a nil slice encodes as the null JSON value.

Thank you for your answers.

@golang golang locked and limited conversation to collaborators Jun 29, 2024
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@bcmills @gopherbot @DiJester @Jorropo