encoding/json: Unmarshal into struct field or a map does not validate invalid json.Number

[brenol]

1. What version of Go are you using (go version)?
   go1.6 linux/amd64
2. What operating system and processor architecture are you using (go env)?
   linux/amd64
3. What did you do?
   (Use play.golang.org to provide a runnable example, if possible.)
   http://play.golang.org/p/8QZq-0vRch
4. What did you expect to see?
   Unmarshal did not accept a invalid JSON as a json.Number, instead, it should raise an error
5. What did you see instead?
   Unmarshal accepted a invalid JSON as a json.Number and did not raise an error
   encoding/json: Encode results in invalid json if json.Number is not a valid number #10281 is the one that actually fixed this issue, however, shouldn't unmarshal should also raise an error? Right now only Marshalling is an raising a error.

@edit
I actually did some further testing and it only happens when Unmarshalling into a struct field, as can be seen in the updated snippet above.

@edit2
It also happens when using map[string]json.Number and I have updated the test case accordingly.

[erikdubbelboer]

This could be fixed by adding the following lines after

go/src/encoding/json/decode.go

Line 915 in 0cc400f

v.SetString(string(s))

if v.Type() == numberType && !isValidNumber(string(s)) {
    d.error(fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", item))
}

The question is if we really want this as it would kinda break how it currently works. People who currently abuse json.Number should switch to json.RawMessage. I'm not sure if this is seen as breaking the Go 1 API.

If you think this would be good to patch I can create a change in gerrit.

[erikdubbelboer]

@bradfitz any input? Otherwise you can close the issue I guess.

[bradfitz]

Sorry, this was stuck in the "Unplanned" limbo state which we have since stopped using.

I don't believe anybody has looked at this. I'll leave the decision on the bug to @rsc.

[rsc]

Leaving for the next round of JSON work.

[gopherbot]

Change https://golang.org/cl/195045 mentions this issue: encoding/json: fix unmarshal invalid json.Number

[mvrhov]

This change just broke the decoding of "field":"" which previously worked and the use of json.Number was on purpose. I don't have the option to change the json input I'm getting.

[odeke-em]

Miha, could you please provide a minimal reproduction that doesn’t work and we can use that for a test case and perhaps for if/when we make a revert? Thank you.

…

On Tue, Feb 18, 2020 at 12:54 AM Miha Vrhovnik ***@***.***> wrote: This change just broke the decoding of "field":"" which previously worked and the use of json.Number was on purpose. I don't have the option to change the json input I'm getting. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#14702?email_source=notifications&email_token=ABFL3V26WX2IDICKSIWWN4TRDOO4PA5CNFSM4B5NVC22YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEMBDUAI#issuecomment-587348481>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABFL3V3MXWFSJUT4DEAOC63RDOO4PANCNFSM4B5NVC2Q> .

[erikdubbelboer]

@odeke-em I guess this is the code @mvrhov is trying to use: https://play.golang.org/p/glvZxWT2to8

@mvrhov If you want to support broken input like that you'll have to use json.RawMessage like this: https://play.golang.org/p/iL5Q62g0Lkm

[mvdan]

Please continue the discussion in #37308. If you have a sample of the real scenario that broke for you, please add it there.