feat: replace go/importer with x/tools/go/packages

Author: n9v9

go.mod

@@ -1,14 +1,17 @@
 module github.com/traefik/mocktail
 
-go 1.22.0
+go 1.23.0
 
 require (
 	github.com/ettle/strcase v0.2.0
 	github.com/stretchr/testify v1.9.0
+	golang.org/x/tools v0.32.0
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/mod v0.24.0 // indirect
+	golang.org/x/sync v0.13.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -2,10 +2,18 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/ettle/strcase v0.2.0 h1:fGNiVF21fHXpX1niBgk0aROov1LagYsOwV/xqKDKR/Q=
 github.com/ettle/strcase v0.2.0/go.mod h1:DajmHElDSaX76ITe3/VHVyMin4LWSJN5Z909Wp+ED1A=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+golang.org/x/mod v0.24.0 h1:ZfthKaKaT4NrhGVZHO1/WDTwGES4De8KtWO0SIbNJMU=
+golang.org/x/mod v0.24.0/go.mod h1:IXM97Txy2VM4PJ3gI61r1YEk/gAj6zAHN3AdZt6S9Ww=
+golang.org/x/sync v0.13.0 h1:AauUjRAJ9OSnvULf/ARrrVywoJDy0YS2AwQ98I37610=
+golang.org/x/sync v0.13.0/go.mod h1:1dzgHSNfp02xaA81J2MS99Qcpr2w7fw1gpm99rleRqA=
+golang.org/x/tools v0.32.0 h1:Q7N1vhpkQv7ybVzLFtTjvQya2ewbwNDZzUgfXGqtMWU=
+golang.org/x/tools v0.32.0/go.mod h1:ZxrU41P/wAbZD8EDa6dDCa6XfpkhJ7HFMjHJXfBDu8s=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

mocktail.go

@@ -7,15 +7,15 @@ import (
 	"flag"
 	"fmt"
 	"go/format"
-	"go/importer"
-	"go/token"
 	"go/types"
 	"io/fs"
 	"log"
 	"os"
 	"path"
 	"path/filepath"
 	"strings"
+
+	"golang.org/x/tools/go/packages"
 )
 
 const (
@@ -77,8 +77,6 @@ func main() {
 func walk(root, moduleName string) (map[string]PackageDesc, error) {
 	model := make(map[string]PackageDesc)
 
-	importR := importer.ForCompiler(token.NewFileSet(), "source", nil)
-
 	err := filepath.WalkDir(root, func(fp string, d fs.DirEntry, err error) error {
 		if err != nil {
 			return err
@@ -131,12 +129,19 @@ func walk(root, moduleName string) (map[string]PackageDesc, error) {
 				importPath = path.Join(moduleName, filePkgName)
 			}
 
-			pkg, err := importR.Import(importPath)
+			pkgs, err := packages.Load(
+				&packages.Config{
+					Mode: packages.NeedTypes,
+					Dir:  root,
+				},
+				importPath,
+			)
 			if err != nil {
-				return fmt.Errorf("failed to import %q: %w", importPath, err)
+				return fmt.Errorf("load package %q: %w", importPath, err)
 			}
 
-			lookup := pkg.Scope().Lookup(interfaceName)
+			// Only one package specified by the import path has been loaded.
+			lookup := pkgs[0].Types.Scope().Lookup(interfaceName)
 			if lookup == nil {
 				log.Printf("Unable to find: %s", interfaceName)
 				continue