x/tools/go/analysis/passes/fieldalignment: suggested fix producing garbled output

[shreyaskarnik]

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

$ go version
go version go1.15.5 darwin/amd64

Does this issue reproduce with the latest release?

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=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/user/work/go/pkg/mod"
GOOS="darwin"
GOPATH="/Users/user/work/go"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.15.5/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.15.5/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/tmp/test-gopls/go.mod"
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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/vh/853pkypj3tnd78rgvfhgc9kr0000gn/T/go-build258818279=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

enabled the following analysis after upgrading to gopls 0.6.0
"analyses": {
"fieldalignment": true
}

What did you expect to see?

Following sample code to demonstrate the issue:

package main

import "fmt"

type Settings struct {
	AllowedEvents []*string // allowed events
	BlockedEvents []*string // blocked events
	APIVersion    string    `mapstructure:"api_version"`
	BaseURL       string    `mapstructure:"base_url"`
	AccessToken   string    `mapstructure:"access_token"`
}
func main() {
	s := &Settings{
		APIVersion:    "",
		BaseURL:       "",
		AccessToken:   "",
		AllowedEvents: []*string{},
		BlockedEvents: []*string{},
	}
	fmt.Println(s)
}

applied fieldalignment codelens in vscode

What did you see instead?

type Settings struct {
	APIVersion    string    `mapstructure:"api_version"`
	BaseURL       string    `mapstructure:"base_url"`
	AccessToken   string    `mapstructure:"access_token"`
	AllowedEvents []*string
	BlockedEvents [ // allowed events
	]*string      // blocked events
}

initially I thought that I made a mistake with the comments so I tried the following struct

type Settings struct {
	// test1
	AllowedEvents []*string
	// test2
	BlockedEvents []*string
	APIVersion    string `mapstructure:"api_version"`
	BaseURL       string `mapstructure:"base_url"`
	AccessToken   string `mapstructure:"access_token"`
}

after applying fieldanalysis codelens to above struct it became garbled too

type Settings struct {
	APIVersion    string `mapstructure:"api_version"`
	BaseURL       string `mapstructure:"base_url"`
	AccessToken   string `mapstructure:"access_token"`
	AllowedEvents [ // test1
	]*string
	BlockedEvents [ // test2
	]*string
}

[stamblerre]

/cc @leitzler

[gopherbot]

Change https://golang.org/cl/278872 mentions this issue: go/analysis/passes/fieldalignment: workaround for garbled output

[leitzler]

@shreyaskarnik could you try to reproduce it with the latest version of gopls? It shouldn't produce garbled output, and CL 278872 should solve that issue. However, due to how AST parsing works right now it is solved by removing comments.

[shreyaskarnik]

@leitzler Thanks for fixing this, it is working as described.