fix: on Windows you must call filepath.Walkdir on the realpath and not the symlink path (#335)

deps.bzl

@@ -21,6 +21,14 @@ def go_dependencies():
         sum = "h1:e6P7q2lk1O+qJJb4BtCQXlK8vWEO8V1ZeuEdJNOqZyg=",
         version = "v0.5.8",
     )
+    go_repository(
+        name = "com_github_yookoala_realpath",
+        build_file_proto_mode = "disable_global",
+        importpath = "github.com/yookoala/realpath",
+        sum = "h1:7OA9pj4FZd+oZDsyvXWQvjn5oBdcHRTV44PpdMSuImQ=",
+        version = "v1.0.0",
+    )
+
     go_repository(
         name = "org_golang_x_exp",
         build_file_proto_mode = "disable_global",

go.mod

@@ -4,5 +4,6 @@ go 1.19
 
 require (
 	github.com/bmatcuk/doublestar/v4 v4.6.0
+	github.com/yookoala/realpath v1.0.0
 	golang.org/x/exp v0.0.0-20221230185412-738e83a70c30
 )

go.sum

@@ -1,4 +1,6 @@
 github.com/bmatcuk/doublestar/v4 v4.6.0 h1:HTuxyug8GyFbRkrffIpzNCSK4luc0TY3wzXvzIZhEXc=
 github.com/bmatcuk/doublestar/v4 v4.6.0/go.mod h1:xBQ8jztBU6kakFMg+8WGxn0c6z1fTSPVIjEY1Wr7jzc=
+github.com/yookoala/realpath v1.0.0 h1:7OA9pj4FZd+oZDsyvXWQvjn5oBdcHRTV44PpdMSuImQ=
+github.com/yookoala/realpath v1.0.0/go.mod h1:gJJMA9wuX7AcqLy1+ffPatSCySA1FQ2S8Ya9AIoYBpE=
 golang.org/x/exp v0.0.0-20221230185412-738e83a70c30 h1:m9O6OTJ627iFnN2JIWfdqlZCzneRO6EEBsHXI25P8ws=
 golang.org/x/exp v0.0.0-20221230185412-738e83a70c30/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=

tools/common/file.go

@@ -1,6 +1,8 @@
 package common
 
-import "path/filepath"
+import (
+	"path/filepath"
+)
 
 // Same as filepath.Rel except that it normalizes result to forward slashes
 // slashes since filepath.Rel will convert to system slashes

tools/copy_directory/BUILD.bazel

@@ -5,7 +5,10 @@ go_library(
     srcs = ["main.go"],
     importpath = "github.com/aspect-build/bazel-lib/tools/copy_directory",
     visibility = ["//visibility:public"],
-    deps = ["//tools/common"],
+    deps = [
+        "//tools/common",
+        "@com_github_yookoala_realpath//:go_default_library",
+    ],
 )
 
 go_binary(

tools/copy_directory/main.go

@@ -5,11 +5,11 @@ import (
 	"io/fs"
 	"log"
 	"os"
-	"path"
 	"path/filepath"
 	"sync"
 
 	"github.com/aspect-build/bazel-lib/tools/common"
+	"github.com/yookoala/realpath"
 )
 
 type pathSet map[string]bool
@@ -46,13 +46,10 @@ func copyDir(src string, dst string) error {
 
 		if info.Mode()&os.ModeSymlink == os.ModeSymlink {
 			// symlink to directories are intentionally never followed by filepath.Walk to avoid infinite recursion
-			linkPath, err := os.Readlink(p)
+			linkPath, err := realpath.Realpath(p)
 			if err != nil {
 				return err
 			}
-			if !path.IsAbs(linkPath) {
-				linkPath = path.Join(path.Dir(p), linkPath)
-			}
 			if srcPaths[linkPath] {
 				// recursive symlink; silently ignore
 				return nil

tools/copy_to_directory/BUILD.bazel

@@ -8,6 +8,7 @@ go_library(
     deps = [
         "//tools/common",
         "@com_github_bmatcuk_doublestar_v4//:doublestar",
+        "@com_github_yookoala_realpath//:go_default_library",
         "@org_golang_x_exp//maps",
     ],
 )

tools/copy_to_directory/main.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/aspect-build/bazel-lib/tools/common"
 	"github.com/bmatcuk/doublestar/v4"
+	"github.com/yookoala/realpath"
 	"golang.org/x/exp/maps"
 )
 
@@ -26,6 +27,7 @@ type fileInfo struct {
 	WorkspacePath string `json:"workspace_path"`
 	Hardlink      bool   `json:"hardlink"`
 
+	Realpath string
 	FileInfo fs.FileInfo
 }
 
@@ -124,7 +126,11 @@ func copyDir(cfg *config, srcPaths pathSet, file fileInfo) error {
 	srcPaths[file.Path] = true
 	// filepath.WalkDir walks the file tree rooted at root, calling fn for each file or directory in
 	// the tree, including root. See https://pkg.go.dev/path/filepath#WalkDir for more info.
-	return filepath.WalkDir(file.Path, func(p string, dirEntry fs.DirEntry, err error) error {
+	walkPath := file.Path
+	if file.Realpath != "" {
+		walkPath = file.Realpath
+	}
+	return filepath.WalkDir(walkPath, func(p string, dirEntry fs.DirEntry, err error) error {
 		if err != nil {
 			return err
 		}
@@ -142,20 +148,17 @@ func copyDir(cfg *config, srcPaths pathSet, file fileInfo) error {
 			return err
 		}
 
-		r, err := common.FileRel(file.Path, p)
+		r, err := common.FileRel(walkPath, p)
 		if err != nil {
 			return err
 		}
 
 		if info.Mode()&os.ModeSymlink == os.ModeSymlink {
 			// symlink to directories are intentionally never followed by filepath.Walk to avoid infinite recursion
-			linkPath, err := os.Readlink(p)
+			linkPath, err := realpath.Realpath(p)
 			if err != nil {
 				return err
 			}
-			if !path.IsAbs(linkPath) {
-				linkPath = path.Join(path.Dir(p), linkPath)
-			}
 			if srcPaths[linkPath] {
 				// recursive symlink; silently ignore
 				return nil
@@ -330,11 +333,28 @@ func copyPath(cfg *config, file fileInfo) error {
 
 func copyPaths(cfg *config) error {
 	for _, file := range cfg.Files {
-		stat, err := os.Stat(file.Path)
+		info, err := os.Lstat(file.Path)
 		if err != nil {
-			return fmt.Errorf("failed to stat file %s: %w", file.Path, err)
+			return fmt.Errorf("failed to lstat file %s: %w", file.Path, err)
 		}
-		file.FileInfo = stat
+
+		if info.Mode()&os.ModeSymlink == os.ModeSymlink {
+			// On Windows, filepath.WalkDir doesn't like directory symlinks so we must
+			// call filepath.WalkDir on the realpath
+			realpath, err := realpath.Realpath(file.Path)
+			if err != nil {
+				return err
+			}
+			stat, err := os.Stat(realpath)
+			if err != nil {
+				return fmt.Errorf("failed to stat file %s pointed to by symlink %s: %w", realpath, file.Path, err)
+			}
+			file.Realpath = realpath
+			file.FileInfo = stat
+		} else {
+			file.FileInfo = info
+		}
+
 		if file.FileInfo.IsDir() {
 			if err := copyDir(cfg, nil, file); err != nil {
 				return err