x/tools/cmd/stringer: document -linecomment in 'go doc stringer'

[tredoe]

This proposal is for that the 'stringer' tool gets flexibility at return strings, because the names that it returns are cased as they are in the values defined.

Problem

type systemKind int

const (
	Windows systemKind = iota
	MacOS
	Linux
	Android
	Ios
)

$ stringer -type systemKind ./test_data/

The names that it generates are WindowsMacOSLinuxAndroidIos.
But sometimes you want show the name of other way, e.g.
"macOS" for "MacOS" or "iOS" for "Ios"

So, the name given to define a constant has not to be the name wanted to be showed into a string.

Also, I would want to get other funcion name to get the string given into a tag string.

Proposal

Using a tag string like str to generate an alternative name, and with an optional tag name (e.g. long) to generate a funcion where return the string.

const (
	Windows systemKind = iota
	MacOS // `str:"macOS"`
	Linux     // `long:"the best system"`
	Android
	Ios // `str:"iOS"`
)

So the method (i systemKind) String() would get WindowsmacOSLinuxAndroidiOS.

And it would add a second method, e.g. (systemKind) LongString()
where it would return "the best system" for the value Linux.

[mvdan]

Duplicate of #20483. See the solution there, which has been implemented for over a year.

[tredoe]

Sorry, but it doesn't solve the issue to generate a second method with other string.

[mvdan]

Sure. You're mixing two proposals, though. Stringer generates exactly one method per type, and extra methods have been rejected in the past. For example, see #23535.

[ianlancetaylor]

The stringer tool is intentionally simple, and making it more complicated will, well, make it more complicated. You can certainly use it as the basis for a tool that does what you want.

[rsc]

@griesemer points out there is an undocumented stringer -linecomment mode that basically does what you are asking for. See https://golang.org/src/cmd/compile/internal/syntax/tokens.go for an example.