missing import black

[ChildWangWorld]

package main

import (
	"github.com/dave/dst/decorator"
	"github.com/dave/dst/decorator/resolver/goast"
	"github.com/dave/dst/decorator/resolver/guess"
	"go/token"
)

func main() {
	code := `package main

import (
	"github.com/opentracing/opentracing-go"
)

var a opentracing.Tracer
`

	dec := decorator.NewDecoratorWithImports(token.NewFileSet(), "main", goast.New())

	f, err := dec.Parse(code)
	if err != nil {
		panic(err)
	}
	res := decorator.NewRestorerWithImports("main", guess.New())
	if err := res.Print(f); err != nil {
		panic(err)
	}
}

get:

package main

var a opentracing.Tracer

expect:

package main

import (
	"github.com/opentracing/opentracing-go"
)

var a opentracing.Tracer

[dave]

Unfortunately with the simple resolvers in the guess and goast packages, there's no way to determine that the name of the github.com/opentracing/opentracing-go package is opentracing.

The guess resolver takes a guess by using the part of the path after the last slash. This fails for many package paths.

You have two options:

1. You can supply a hardcoded mapping that tells the resolver what the package names are (example shown below).

2. Alternatively you can use the more fully featured gotypes and gopackages resolvers.

There's a Go2 proposal that would fix all this complexity here. Feel free to give it a thunbs-up!

package main

import (
	"github.com/dave/dst/decorator"
	"github.com/dave/dst/decorator/resolver/goast"
	"github.com/dave/dst/decorator/resolver/guess"
	"go/token"
)

func main() {
	code := `package main

import (
	"github.com/opentracing/opentracing-go"
)

var a opentracing.Tracer
`
	packageNames := map[string]string{"github.com/opentracing/opentracing-go" : "opentracing"}
	packageNameResolver := guess.WithMap(packageNames)
	decoratorResolver := goast.WithResolver(packageNameResolver)

	dec := decorator.NewDecoratorWithImports(token.NewFileSet(), "main", decoratorResolver)

	f, err := dec.Parse(code)
	if err != nil {
		panic(err)
	}
	
	res := decorator.NewRestorerWithImports("main", packageNameResolver)
	if err := res.Print(f); err != nil {
		panic(err)
	}
}

Output:

package main

import (
	"github.com/opentracing/opentracing-go"
)

var a opentracing.Tracer

[dave]

One more possible solution... I assumed you need dst to manage the import block automatically, but if this is not the case, then you can just remove the resolvers entirely and it won't modify the import block at all:

package main

import (
	"github.com/dave/dst/decorator"
	"go/token"
)

func main() {
	code := `package main

import (
	"github.com/opentracing/opentracing-go"
)

var a opentracing.Tracer
`
	dec := decorator.NewDecorator(token.NewFileSet())

	f, err := dec.Parse(code)
	if err != nil {
		panic(err)
	}
	
	res := decorator.NewRestorer()
	if err := res.Print(f); err != nil {
		panic(err)
	}
}

Output:

package main

import (
	"github.com/opentracing/opentracing-go"
)

var a opentracing.Tracer

[ChildWangWorld]

thx 😁