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log/slog: LogValue not called pointer receiver vs value #60962

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mvrhov opened this issue Jun 23, 2023 · 3 comments
Closed

log/slog: LogValue not called pointer receiver vs value #60962

mvrhov opened this issue Jun 23, 2023 · 3 comments

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@mvrhov
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mvrhov commented Jun 23, 2023

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

$ go version
go version go1.21rc2 linux/amd64

Does this issue reproduce with the latest release?

YES

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

go env Output
$ go env

go env

GO111MODULE=''

GOARCH='amd64'

GOBIN='/srv/go/bin'

GOCACHE='/home/miha/.cache/go-build'

GOENV='/home/miha/.config/go/env'

GOEXE=''

GOEXPERIMENT=''

GOFLAGS=''

GOHOSTARCH='amd64'

GOHOSTOS='linux'

GOINSECURE=''

GOMODCACHE='/srv/go/pkg/mod'

GONOPROXY=''

GONOSUMDB=''

GOOS='linux'

GOPATH='/srv/go'

GOPRIVATE=''

GOPROXY='https://proxy.golang.org,direct'

GOROOT='/usr/local/go'

GOSUMDB='sum.golang.org'

GOTMPDIR=''

GOTOOLCHAIN='auto'

GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'

GOVCS=''

GOVERSION='go1.21rc2'

GCCGO='gccgo'

GOAMD64='v1'

AR='ar'

CC='gcc'

CXX='g++'

CGO_ENABLED='1'

GOMOD='/dev/null'

GOWORK=''

CGO_CFLAGS='-O2 -g'

CGO_CPPFLAGS=''

CGO_CXXFLAGS='-O2 -g'

CGO_FFLAGS='-O2 -g'

CGO_LDFLAGS='-O2 -g'

PKG_CONFIG='pkg-config'

GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3497984750=/tmp/go-build -gno-record-gcc-switches'

What did you do?

type Foo struct {
	V1 uint64
	V2 uint64
}

func (f *Foo) String() string {
	return fmt.Sprintf("%d %d", f.V1, f.V2)
}

func (f *Foo) LogValue() slog.Value {
	return slog.GroupValue(slog.String("string", "s"),
		slog.Group("i", slog.Uint64("v1", f.V1), slog.Uint64("v2", f.V2)))
}

func init() {
	t := Foo{
		V1: 345_678,
		V2: 10_000,
	}

	l := slog.New(slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{}))
	l.LogAttrs(context.Background(), slog.LevelInfo, "test value", slog.Any("t", t))
	l.LogAttrs(context.Background(), slog.LevelInfo, "test pointer", slog.Any("t", &t))
}

What did you expect to see?

{"time":"2023-06-23T12:42:53.827957997+02:00","level":"INFO","msg":"test value","t":{"string":"s","i":{"v1":345678,"v2":10000}}}
{"time":"2023-06-23T12:42:53.828082686+02:00","level":"INFO","msg":"test pointer","t":{"string":"s","i":{"v1":345678,"v2":10000}}}

What did you see instead?

{"time":"2023-06-23T12:42:53.827957997+02:00","level":"INFO","msg":"test value","t":{"V1":345678,"V2":10000}}
{"time":"2023-06-23T12:42:53.828082686+02:00","level":"INFO","msg":"test pointer","t":{"string":"s","i":{"v1":345678,"v2":10000}}}
@cuonglm
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cuonglm commented Jun 23, 2023

Seems working as expected to me, &t is a slog.LogValuer, but t is not.

@seankhliao seankhliao closed this as not planned Won't fix, can't repro, duplicate, stale Jun 23, 2023
@mvrhov
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mvrhov commented Jun 29, 2023

If this is expected behavior, Then the go tour should be changed/ fixed, because it's saying to NOT have mixed methods on type, e.g on value and pointer receiver methods.

@cuonglm
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cuonglm commented Jun 29, 2023

If this is expected behavior, Then the go tour should be changed/ fixed, because it's saying to NOT have mixed methods on type, e.g on value and pointer receiver methods.

I'm not sure it's related.

  • What go tour said mean you should declare all methods of a type using either only pointer receiver, or only value receiver. This is true in this example, all methods are declared with pointer receiver.

  • The issue here is that method with value receiver of type T will be available for type *T, but not vice versa. That mean *Foo is a LogValuer, but Foo is not, because Foo don't have LogValue method.

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3 participants
@mvrhov @cuonglm @seankhliao