为何不同Go版本中go vet对重复JSON标签的检测结果不同？

Great question—this boils down to targeted tweaks to the go vet tool's rule set between Go 1.12.4 and 1.12.7. Let's break this down clearly:

• First, recap your scenario: You have a nested struct setup where an embedded Something struct has a field tagged json:"number", and the outer SomethingWithBattery struct also defines its own Number field with the exact same json:"number" tag.
• In Go 1.12.4, go vet flags this as an error, treating the duplicate JSON tag as a critical conflict. But in 1.12.7, this check was adjusted, so go vet no longer reports it.

What changed under the hood? #

Go's team regularly refines the go vet tool in minor releases to fix false positives and refine checks. In this case, the original 1.12.4 check was overly strict—it didn't account for how embedded structs interact with outer fields during JSON processing.

When you have an embedded struct and an outer field sharing the same JSON tag, the outer field takes full precedence during serialization/deserialization (it effectively overrides the embedded field's tag). The Go team recognized this is a valid, intentional pattern in some use cases, so they updated go vet in 1.12.7 to stop flagging this scenario as an error.

How to verify this? #

If you dig into the patch notes between Go 1.12.4 and 1.12.7, you'll find that the vet tool's struct tag conflict check was adjusted to exclude cases where duplicates come from an embedded struct and an explicitly defined outer field. This was a direct fix for a false positive that was incorrectly flagging valid code.

So the discrepancy you're seeing is just the result of a small, targeted improvement to go vet's rules in a minor Go update.

内容的提问来源于stack exchange，提问作者poolsideDev