Feature request: expose file names of files loaded through decorator.Load

[mejibyte]

Hi there! Thank you so much for this awesome library!

I want to write a small refactoring tool. The idea is to load a package, move some things around using dst, and then write the changes back to disk. I am able to load my package, do changes and print the result of each file to stdout with code like this:

func featureRequest() {
	dir := "/tmp/t"
	pkgs, err := decorator.Load(&packages.Config{Dir: dir, Mode: packages.LoadSyntax}, "root")
	if err != nil {
		panic(err)
	}
	p := pkgs[0]
	fmt.Printf("parsed %d files\n", len(p.Syntax))
	for _, f := range p.Syntax {
		b := f.Decls[0].(*dst.FuncDecl).Body
		b.List = append(b.List, &dst.ExprStmt{
			X: &dst.CallExpr{
				Fun: &dst.Ident{Path: "fmt", Name: "Println"},
				Args: []dst.Expr{
					&dst.BasicLit{Kind: token.STRING, Value: strconv.Quote("Hello, World!")},
				},
			},
		})

		fmt.Println("=====================================")
		r := decorator.NewRestorerWithImports("root", gopackages.New(dir))
		if err := r.Print(f); err != nil {
			panic(err)
		}
	}
}

This successfully loads the files, applies changes and resolves the imports (great!). Here's the output of calling the function above (I have these files in my /tmp/t directory: main.go, sum.go and go.mod):

$ go run ./cmd/refactorer/main.go 
parsed 2 files
=====================================
package main

import "fmt"

func sum(int x, int y) {
	_ = x + y
	fmt.Println("Hello, World!")
}
=====================================
package main

import "fmt"

func main() { fmt.Println("Hello, World!") }

However, as far as I could see, the paths of .go files that were loaded are not exposed anywhere. This means at the moment I can't write the changes back to disk because I don't know which parsed file inside p.Syntax corresponds to which path.

It would be awesome if we could expose the file names in the struct returned by decorator.Load, perhaps by converting Syntax:

dst/decorator/load.go

Line 96 in ce1c8af

Syntax []*dst.File

to a map where keys are filenames, similar to:

dst/dst.go

Line 674 in ce1c8af

Files map[string]*File // Go source files by filename

.

[dave]

I think Decorator.Filenames is what you're looking for?

so:

...
	for _, f := range p.Syntax {
		fmt.Println("Filename:", p.Decorator.Filenames[f]) // <---- ADD THIS
...

[mejibyte]

@dave yup, that worked! I can't believe I missed that one. Thanks a lot!