x/tools/gopls: Provide automatic conversion of structure A to structure B

[tttoad]

gopls version

Build info ---------- golang.org/x/tools/gopls v0.15.0-pre.1 golang.org/x/tools/gopls@v0.15.0-pre.1 h1:u87rDKpsE6ax0cASyD9mJW9If25TtW0IupV6vKDDevg= github.com/BurntSushi/toml@v1.2.1 h1:9F2/+DoOYIOksmaJFPw1tGFy1eDnIJXg+UHjuD8lTak= github.com/google/go-cmp@v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38= golang.org/x/exp/typeparams@v0.0.0-20221212164502-fae10dda9338 h1:2O2DON6y3XMJiQRAS1UWU+54aec2uopH3x7MAiqGW 6Y= golang.org/x/mod@v0.14.0 h1:dGoOF9QVLYng8IHTm7BAyWqCqSheQ5pYWGhzW00YJr0= golang.org/x/sync@v0.5.0 h1:60k92dhOjHxJkrqnwsfl8KuaHbn/5dl0lUPUklKo3qE= golang.org/x/telemetry@v0.0.0-20231114163143-69313e640400 h1:brbkEFfGwNGAEkykUOcryE/JiHUMMJouzE0fWWmz/QU= golang.org/x/text@v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ= golang.org/x/tools@v0.16.2-0.20240105173808-36a523fefd90 h1:3dw2Y1Aes2o83VYvSZSPc+p70AuT9zvNCTBHCvUUZrE= golang.org/x/vuln@v1.0.1 h1:KUas02EjQK5LTuIx1OylBQdKKZ9jeugs+HiqO5HormU= honnef.co/go/tools@v0.4.5 h1:YGD4H+SuIOOqsyoLOpZDWcieM28W47/zRO7f+9V3nvo= mvdan.cc/gofumpt@v0.4.0 h1:JVf4NN1mIpHogBj7ABpgOyZc65/UUOkKQFkoURsz4MM= mvdan.cc/xurls/v2@v2.4.0 h1:tzxjVAj+wSBmDcF6zBB7/myTy3gX9xvi8Tyr28AuQgc= go: go1.21.5

go env

GO111MODULE=''
GOARCH='arm64'
GOBIN=''
GOCACHE='/Users/toad/Library/Caches/go-build'
GOENV='/Users/toad/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/toad/work/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/toad/work'
GOPRIVATE=''
GOPROXY='https://goproxy.cn,direct'
GOROOT='/Users/toad/go/go1.21.5'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/Users/toad/go/go1.21.5/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.21.5'
GCCGO='gccgo'
AR='ar'
CC='cc'
CXX='clang++'
CGO_ENABLED='1'
GOMOD='/Users/toad/work/demo1/go.mod'
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 -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-pref
ix-map=/var/folders/g1/tgmnlrdn3vxgv08kdgh9vpkw0000gn/T/go-build2737097617=/tmp/go-build -gno-record-gcc-switch
es -fno-common'

What did you do?

Call code actions in a=b

type AA struct {
	CCC string
	EEE string
	BBB int
}

type BB struct {
	CCC string
	BBB int 
	DDD string
}


func main() {
	var (
		a AA
		b BB
	)

	a=b
}

What did you see happen?

no code actions.

What did you expect to see?

There are code actions that support automatic conversion.

func main() {
	var (
		a AA
		b BB
	)

	a = AA{
		CCC: b.CCC,
		BBB: b.BBB,
	}
}

Editor and settings

No response

Logs

No response

[tttoad]

@gopherbot, please add label FeatureRequest

[findleyr]

Can you describe the precise way you'd like this feature to work? If there are any fields in b whose names match fields in a, generate a composite literal mapping those fields? What if there are methods with matching name and type on B, should we invoke them?

I feel like such a feature would be rarely needed. Do you find that you would use this feature often?

[tttoad]

@findleyr

I feel like such a feature would be rarely needed. Do you find that you would use this feature often?

Yes, I use this feature quite often.
In our service, different struct are used between different layers.
example:

// Request struct
type AddUser struct {
        Name  string
	Addr  string
	RequestID string // or other field.
}

// User Table struct
// This structure maps one-to-one to the database table fields.
type UserTable struct {
      Name string
      Addr  string
}

If there are any fields in b whose names match fields in a, generate a composite literal mapping those fields?

Yes.
It would be nice to deal with composite data structures.
Like B.UserID -> A.User.ID

type AA struct {
	User
}

type User struct{
         ID string
}

type BB struct {
	UserID string
}

a = AA{
	User: User{
		ID: b.UserID,
	},
}

What if there are methods with matching name and type on B, should we invoke them?

Yes.
It should support methods that start with Get.
I often need to convert structures in protobuf to my self.

[tttoad]

@findleyr Any news on this?
I am willing to provide the implementation of the feature if you agree.