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cmd/gofmt: inconsistent indentation of struct fields of containing tab #51910

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fraenky8 opened this issue Mar 24, 2022 · 4 comments
Closed

cmd/gofmt: inconsistent indentation of struct fields of containing tab #51910

fraenky8 opened this issue Mar 24, 2022 · 4 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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@fraenky8
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What version of Go are you using (go version)?

$ go version
go version go1.18 darwin/amd64

Does this issue reproduce with the latest release?

Yes, also playground.

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

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/user/Library/Caches/go-build"
GOENV="/Users/user/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/user/Coding/Go/pkg/mod"
GOOS="darwin"
GOPATH="/Users/user/Coding/Go"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.18/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.18/libexec/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.18"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="clang"
CXX="clang++"
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 -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/8v/jgh2dzcn62n0lfyws13mc_rw0000gp/T/go-build3442110454=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Run gofmt -d on the following program

https://go.dev/play/p/bVJxvovrvWB

package main

import "fmt"

type S struct {
	S       string
	Integer int //  extra long field name to point out the indentation
}

func main() {
	s := []S{
		{
			S:       "Hello World",
			Integer: 42,
		},
		{
			S:       "\t",
			Integer: 42,
		},
		{
			S:       "	", // an actual <tab>
			Integer: 42,
		},
		{
			S:       `	`, // an actual <tab>
			Integer: 42,
		},
		{
			S:       "\u0009",
			Integer: 42,
		},
	}

	fmt.Printf("%#v", s)
}

What did you expect to see?

	s := []S{
		{
			S:       "Hello World",
			Integer: 42,
		},
		{
			S:       "\t",
			Integer: 42,
		},
		{
			S:       "	", // an actual <tab>
			Integer: 42,
		},
		{
			S:       `	`, // an actual <tab>
			Integer: 42,
		},
		{
			S:       "\u0009",
			Integer: 42,
		},
	}

What did you see instead?

The fields with the actual tab-value are not indented as expected. Is this expected behavior?

	s := []S{
		{
			S:       "Hello World",
			Integer: 42,
		},
		{
			S:       "\t",
			Integer: 42,
		},
		{
			S: "	", // an actual <tab>
			Integer: 42,
		},
		{
			S: `	`, // an actual <tab>
			Integer: 42,
		},
		{
			S:       "\u0009",
			Integer: 42,
		},
	}
@seankhliao seankhliao changed the title gofmt: inconsistent indentation of struct fields of type string cmd/gofmt: inconsistent indentation of struct fields of containing tab Mar 24, 2022
@mknyszek
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Is this new in Go 1.18?

CC @griesemer via https://dev.golang.org/owners

@mknyszek mknyszek added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Mar 24, 2022
@mknyszek mknyszek added this to the Backlog milestone Mar 24, 2022
@griesemer
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griesemer commented Mar 24, 2022 •
edited

This doesn't look like a new issue; I can reproduce this with Go 1.16. Looks like some unexpected interaction of the "actual " character with the formatting routine (tabwriter) which uses tabs for alignment, even though in the case of literal strings (as we have here), the string contents should be protected from such interaction.

cc: @mvdan any interest in looking into this?

@gopherbot
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Change https://go.dev/cl/404955 mentions this issue: go/printer: align expression list elements containing tabs

@mvdan
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mvdan commented May 8, 2022

Fix sent :) Definitely one of those that took longer to debug than to actually fix.

The literals are indeed escaped from the tabwriter. The problem was in the code that predicts the size of each node as printed on a single line; it got confused by tab characters.

@liggitt liggitt mentioned this issue Jul 25, 2022
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@golang golang locked and limited conversation to collaborators May 10, 2023
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@mknyszek @mvdan @fraenky8 @griesemer @gopherbot