Golang encoding/json/v2: unexpected support for Inf in map[string]any value

inf := math.Inf(1)
json.Marshal(inf)
json.Marshal(struct{ F float64 }{inf})
json.Marshal(map[string]any{"k": inf})

v1 returns "json: unsupported value: +Inf" in all three cases.

v2 (including v1 with GOEXPERIMENT=jsonv2) returns "json: unsupported value: +Inf" in the first two cases, but succeeds and returns {"k":"Infinity"} in the third case.

Seems like an unintentional change? I'd expect all three cases to succeed or fail.

Comment From: neild

/cc @dsnet

Comment From: gabyhelp

Related Issues

• encoding/json: please document that float +inf/-inf/nan will cause json.Marshal return error #59627 (closed)

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Comment From: dsnet

This works correctly if you set the optimizeCommon constant to false, which indicates that the optimized implementation is wrong.

Comment From: gopherbot

Change https://go.dev/cl/695276 mentions this issue: encoding/json/v2: fix incorrect marshaling of NaN in float64 any