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encoding/json: rendered empty struct on omitempty #59170

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IGLOU-EU opened this issue Mar 21, 2023 · 2 comments
Closed

encoding/json: rendered empty struct on omitempty #59170

IGLOU-EU opened this issue Mar 21, 2023 · 2 comments
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@IGLOU-EU
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IGLOU-EU commented Mar 21, 2023 •
edited

What version of Go are you using (go version)?

$ go version
go version go1.20 linux/amd64

What did you do?

Marshal a struct into Json with omitempty.
https://go.dev/play/p/nTyS0p_JP3E

type A struct {
	AA string `json:"aa,omitempty"`
	AB []struct {
		ABA int    `json:"aba,omitempty"`
		ABB string `json:"abb,omitempty"`
	} `json:"ab,omitempty"`
	AC struct {
		ACA int `json:"aca,omitempty"`
	} `json:"ac,omitempty"`
}

func main() {
	a, b := json.Marshal(A{AA: "Hum"})
	fmt.Printf("%s\n%v", a, b)
}

What did you expect to see?

{"aa":"Hum"}

What did you see instead?

{"aa":"Hum","ac":{}}
@zephyrtronium
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See also #11939 and #45669, and tangentially #22480. This is working as currently documented:

The "omitempty" option specifies that the field should be omitted from the encoding if the field has an empty value, defined as false, 0, a nil pointer, a nil interface value, and any empty array, slice, map, or string.

With respect to omitempty, there is no "empty" value of any struct type.

@IGLOU-EU
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Thank you, that true. I go read their's proposal !

@golang golang locked and limited conversation to collaborators Mar 20, 2024
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@zephyrtronium @gopherbot @IGLOU-EU