Build package paths correctly on Windows

Addresses vektra#722

pkg/config/config.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"path"
 	"reflect"
 	"regexp"
 	"strings"
@@ -469,8 +470,6 @@ func isAutoGenerated(path *pathlib.Path) (bool, error) {
 func (c *Config) subPackages(
 	ctx context.Context,
 	pkgPath string,
-	pkgConfig *Config,
-	currentDepth int,
 ) ([]string, error) {
 	log := zerolog.Ctx(ctx)
 
@@ -482,7 +481,7 @@ func (c *Config) subPackages(
 	}
 	pkg := pkgs[0]
 
-	if currentDepth == 0 && len(pkg.GoFiles) == 0 {
+	if len(pkg.GoFiles) == 0 {
 		log.Error().
 			Err(ErrNoGoFilesFoundInRoot).
 			Str("documentation", logging.DocsURL("/notes/#error-no-go-files-found-in-root-search-path")).
@@ -493,7 +492,7 @@ func (c *Config) subPackages(
 	searchRoot := representativeFile.Parent()
 	packageRootName := pathlib.NewPath(pkg.PkgPath)
 	packageRootPath := searchRoot
-	subPackages := []string{}
+	var subPackages []string
 
 	walker, err := pathlib.NewWalk(
 		searchRoot,
@@ -507,7 +506,7 @@ func (c *Config) subPackages(
 	}
 
 	visitedDirs := map[string]any{}
-	subdirectoriesWithGoFiles := []*pathlib.Path{}
+	var subdirectoriesWithGoFiles []*pathlib.Path
 
 	// We consider the searchRoot to already be visited because
 	// we know it's already in the configuration.
@@ -555,8 +554,13 @@ func (c *Config) subPackages(
 			log.Err(err).Stringer("root", packageRootPath).Stringer("subRoot", d).Msg("failed to make subroot relative to root")
 			return nil, fmt.Errorf("failed to make subroot relative to root: %w", err)
 		}
-		absolutePackageName := packageRootName.Join(relativeFilesystemPath.Parts()...)
-		subPackages = append(subPackages, absolutePackageName.String())
+		partsToJoin := []string{packageRootName.String()}
+		partsToJoin = append(partsToJoin, relativeFilesystemPath.Parts()...)
+		// we use path.Join here because the package path is always /-separated
+		// regardless of os.PathSeparator (i.e. even on Windows)
+		absolutePackageName := path.Join(partsToJoin...)
+
+		subPackages = append(subPackages, absolutePackageName)
 	}
 
 	return subPackages, nil
@@ -587,7 +591,7 @@ func (c *Config) discoverRecursivePackages(ctx context.Context) error {
 		pkgLog := log.With().Str("package-path", pkgPath).Logger()
 		pkgCtx := pkgLog.WithContext(ctx)
 		pkgLog.Debug().Msg("discovering sub-packages")
-		subPkgs, err := c.subPackages(pkgCtx, pkgPath, conf, 0)
+		subPkgs, err := c.subPackages(pkgCtx, pkgPath)
 		if err != nil {
 			return fmt.Errorf("failed to get subpackages: %w", err)
 		}