x/tools/cmd/stringer cannot run on a file containing imports

[0xjac]

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

$ go version
go version go1.18 linux/amd64

Does this issue reproduce with the latest release?

Yes, and with all available versions of golang.org/x/tools from v0.1.0 to v.0.1.10 included.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="$HOME/.cache/go-build"
GOENV="$HOME/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="$HOME/go/pkg/mod"
GONOPROXY="[REDACTED]"
GONOSUMDB="[REDACTED]"
GOOS="linux"
GOPATH="$HOME/go"
GOPRIVATE="[REDACTED]"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1257915923=/tmp/go-build -gno-record-gcc-switches"

What did you do?

stringer fails to generate a String method for a type located in a file which contains (unrelated) valid imports.

Consider the following pill.go file taken from the stringer documentation, with an extra silly Print function whose sole purpose here is to add an import statement (fmt):

package pill

import (
	"fmt"
)

type Pill int

const (
	Placebo Pill = iota
	Aspirin
	Ibuprofen
	Paracetamol
	Acetaminophen = Paracetamol
)

func Print(pill Pill) {
	fmt.Printf("%v", pill)
}

This needs to be placed in a go module, the simplest reproducible example is to put the file above alongside a simple go.mod file in a pill directory such as:

./pill
├── go.mod
└── pill.go

The go.mod file can be created with go mod init pill.

Simply run the stringer command as documented:

stringer -type=Pill

What did you expect to see?

A correctly generated file: pill_string.go which contains the implementation of the String method for the type Pill defined in the file pill.go (above) as per the stringer documentation.

What did you see instead?

When running the command on the file above, no pill_string.go file is generated. Instead we get the following error message:

stringer: internal error: package "fmt" without types was imported from "pill"

Note this is most likely a consequence of #37617.

[dr2chase]

I tried to reproduce this, including with the latest version of stringer

go install golang.org/x/tools/cmd/stringer@latest
go: downloading golang.org/x/sys v0.0.0-20211019181941-9d821ace8654

and got some errors that were even more mystifying

stringer -type=Pill
stringer: checking package: pill.go:4:2: could not import fmt (cannot find package "fmt" in any of:
	/.../home/drchase/work/go-ssa/src/fmt (from $GOROOT)
	/.../home/drchase/go/src/fmt (from $GOPATH))

but there is no "GO"-anything in my environment, nor is there any mention of "ssa" and the error persisted after go clean -cache.

[dr2chase]

@golang/tools-team can you give this a look?

[findleyr]

Hi, can you please try go clean -cache, and check if the problem persists?

[0xjac]

@findleyr I've just tried with both go clean -cache and go clean -modcache and the result stays the same:

stringer: internal error: package "fmt" without types was imported from "pill"

Even more interesting, I've cloned the tools repo, checked out v0.1.10 (6799a7ae) and ran stringer from there.

From my pill module, adjacent to go tools if I build stringer.go and there run it from my pill, it works. I get no output but the string file is generated correctly!?

$ pushd ../go-tools/cmd/stringer/; go build stringer.go; popd; ../go-tools/cmd/stringer/stringer -type=Pill
$ head -n 1 pill_string.go
// Code generated by "stringer -type=Pill"; DO NOT EDIT.

This is reaching my limit of go knowledge... I don't understand why the version of stringer built locally with go build (no option) works, but the version installed via go get golang.org/x/tools/cmd/stringer does not...

Note that together with go build, I tried go install (from tools/cmd/stringer) to replace the stringer binary installed via go get with the one built locally and that also result in a working binary.

This all seems rather confusing but I hope someone can make sense of it. I'm happy to help debug further if needed.

[findleyr]

I can't reproduce. How are you installing stringer?

Heres what I've done:

> go install golang.org/x/tools/cmd/stringer@latest
> go version
go version devel go1.19-61a585a32c Tue May 3 16:29:56 2022 +0000 linux/amd64
> stringer -type=Pill
> ls
go.mod  pill.go  pill_string.go
> go1.18beta1 install golang.org/x/tools/cmd/stringer@latest
> stringer -type=Pill
> ls
go.mod  pill.go  pill_string.go
> nvim pill_string.go

i.e. with both the go1.18 beta and a recent go1.19 build, installing the latest version of stringer works fine.

[seankhliao]

@0xjac output of go version -m /path/to/stringer please
also go get shouldn't be installing anything.

[0xjac]

@seankhliao thanks for your comment, I am not sure why go get seemed to have executed successfully and silently if it is not supposed to install anything.

I believe this might have been user error on my part, where go get -u golang.org/x/tools/cmd/stringer only updated the dependency in my module but did not update the stringer binary. And I must have had an old version of stringer back from when it was installed with go get instead of go install. I've manually removed the stringer manually, cleaned the cache and reinstalled it with go install and with v0.10.0 it now works.

I've checked old versions and if I downgrade to v0.1.7 then I get the error message. Most likely that issue was fixed for v0.1.8 so that's on me...

With the latest version (v0.1.10) of stringer, the output of go version -m `which stringer` is:

/home/jac/go/bin/stringer: go1.18
	path	golang.org/x/tools/cmd/stringer
	mod	golang.org/x/tools	v0.1.10	h1:QjFRCZxdOhBJ/UNgnBZLbNV13DlbnK0quyivTnXJM20=
	dep	golang.org/x/mod	v0.6.0-dev.0.20220106191415-9b9b3d81d5e3	h1:kQgndtyPBW/JIYERgdxfwMYh3AVStj88WQTlNDi2a+o=
	dep	golang.org/x/sys	v0.0.0-20211019181941-9d821ace8654	h1:id054HUawV2/6IGm2IV8KZQjqtwAOo2CYlOToYqa0d0=
	dep	golang.org/x/xerrors	v0.0.0-20200804184101-5ec99f83aff1	h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
	build	-compiler=gc
	build	CGO_ENABLED=1
	build	CGO_CFLAGS=
	build	CGO_CPPFLAGS=
	build	CGO_CXXFLAGS=
	build	CGO_LDFLAGS=
	build	GOARCH=amd64
	build	GOOS=linux
	build	GOAMD64=v1

For me this is solved, with my apology for anyone's time being wasted and a special thanks to @seankhliao who made me realize where I got it wrong. 😉

The issue of @dr2chase remains however. But I can't reproduce it. As I started this I am happy to help solve it. @dr2chase did you put the pill.go file in its own directory alongside a go.mod file to make it a module?

[findleyr]

Closing as I think the issue @dr2chase is encountering is a separate problem, perhaps related to his environment.

[AdwindOne]

go version 1.18.5 success but 1.20 has the same error

[adonovan]

I can't reproduce the problem at 1.20 or at tip:

dummy$ pwd
/Users/adonovan/w/dummy
dummy$ ls
go.mod	pill.go
dummy$ head -999 * 
==> go.mod <==
module dummy.com

go 1.19

==> pill.go <==
package dummy

import (
"fmt"
)

type Pill int

const (
	Placebo Pill = iota
	Aspirin
	Ibuprofen
	Paracetamol
	Acetaminophen = Paracetamol
)

func Print(pill Pill) {
	fmt.Printf("%v", pill)
}
dummy$ go1.20 run golang.org/x/tools/cmd/stringer@latest -type=Pill 
dummy$ ls
go.mod		pill.go		pill_string.go
dummy$ cat pill_string.go 
// Code generated by "stringer -type=Pill"; DO NOT EDIT.

package dummy

import "strconv"

func _() {
	// An "invalid array index" compiler error signifies that the constant values have changed.
	// Re-run the stringer command to generate them again.
	var x [1]struct{}
	_ = x[Placebo-0]
	_ = x[Aspirin-1]
	_ = x[Ibuprofen-2]
	_ = x[Paracetamol-3]
}

const _Pill_name = "PlaceboAspirinIbuprofenParacetamol"

var _Pill_index = [...]uint8{0, 7, 14, 23, 34}

func (i Pill) String() string {
	if i < 0 || i >= Pill(len(_Pill_index)-1) {
		return "Pill(" + strconv.FormatInt(int64(i), 10) + ")"
	}
	return _Pill_name[_Pill_index[i]:_Pill_index[i+1]]
}
dummy$ 

@AdwindOne Is your go.mod file valid? Can you provide the output of go1.20 list -json . in the pill directory?