proposal: cmd/go: go fmt - align all labels

[cn0047]

Does it make sense to improve go fmt and align all struct's labels not only first one:

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

go version go1.11 darwin/amd64

Does this issue reproduce with the latest release?

yes

What did you do?

go fmt

What did you expect to see?

type MyData struct {
  ID        string `json:"id"         datastore:"id"`
  FirstName string `json:"first_name" datastore:"first_name"`
}

What did you see instead?

type MyData struct {
  ID        string `json:"id" datastore:"id"`
  FirstName string `json:"first_name" datastore:"first_name"`
}

[cznic]

The string field tag has no defined format. gofmt has no idea what the content of the struct tag will be used for and it is never safe to modify it in any way by a program which purpose is to canonicalize white space between tokens.

[agnivade]

Yes, technically the entire text between `` is a single tag. Anything inside that is free-form text. So gofmt should not perform anything inside that.

I think there are several proposals to make tags typed. Before that, I don't think we should do any sort of parsing of tags.

[mvdan]

I'll leave it to @griesemer to make the final decision, but I agree that this is not a job for gofmt. It works on syntax alone, and the program is not supposed to modify arbitrary literals.

[griesemer]

The language spec doesn't say anything about the contents of field tags; thus gofmt cannot make assumptions about their content.

It's fine if someone wants to use a tool that does this alignment, but it should be separate and must be used with knowledge of the tag's content.

[rsc]

Agree that this is not gofmt's job. Declining per @griesemer's comment.