proposal: x/tools/cmd/stringer: add -scanner

[TonyRippy]

Proposal Details

In addition to being able go from a type to a string, it would be useful to parse a string back into a type value.

I propose adding a new -scanner option that would tell the stringer tool to also generate a fmt.Scanner implementation that accepts the "%s" verb. It makes sense to include this as part of x/tools/cmd/stringer because the implmentation can make use of the generated _Type_name and _Type_index array.

An example of use:

import "fmt"

type MyType uint64
const (
  One MyType = iota
  Two
  Three
)
//go:generate stringer -type=MyType -scanner

func Example(v MyType) {
  stringerOutput := fmt.Sprintf("<%s>", v)
  var v2 MyType
  _, err := fmt.Sscanf(stringerOutput, "<%s>", &v2)
  if err != nil {
    panic(err)
  }
  if v2 != v {
    panic("the values should match")
  }
} 

I have an implementation that I have used in a private project, and I would like to contribute it back to the Go project. This proposal would provide a solution for the earlier request #60228.

[gabyhelp]

Related Issues

• proposal: x/tools/stringer: add a Parse function to go from string to value #55860 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[TonyRippy]

Wow, that "Related Issues" search is handy... I swear I looked through the existing issues, but somehow didn't see that one.

[seankhliao]

Duplicate of #23535