Try to fix failing tests on Windows

modules/caddyhttp/caddyhttp.go

@@ -227,9 +227,9 @@ func StatusCodeMatches(actual, configured int) bool {
 // be a trusted path, but reqPath is not; and the output will
 // never be outside of root. The resulting path can be used
 // with the local file system. If root is empty, the current
-// directory is assumed. If the cleaned request path is not
-// lexically local, it will be rejected as unsafe and only
-// the root will be returned.
+// directory is assumed. If the cleaned request path is deemed
+// not local according to lexical processing (i.e. ignoring links),
+// it will be rejected as unsafe and only the root will be returned.
 func SanitizedPathJoin(root, reqPath string) string {
 	if root == "" {
 		root = "."
@@ -241,7 +241,7 @@ func SanitizedPathJoin(root, reqPath string) string {
 		return root
 	}
 
-	path := filepath.Join(root, relPath)
+	path := filepath.Join(root, filepath.FromSlash(relPath))
 
 	// filepath.Join also cleans the path, and cleaning strips
 	// the trailing slash, so we need to re-add it afterwards.

modules/caddyhttp/caddyhttp_test.go

@@ -3,6 +3,7 @@ package caddyhttp
 import (
 	"net/url"
 	"path/filepath"
+	"runtime"
 	"testing"
 )
 
@@ -12,9 +13,10 @@ func TestSanitizedPathJoin(t *testing.T) {
 	// %2f = /
 	// %5c = \
 	for i, tc := range []struct {
-		inputRoot string
-		inputPath string
-		expect    string
+		inputRoot     string
+		inputPath     string
+		expect        string
+		expectWindows string
 	}{
 		{
 			inputPath: "",
@@ -81,9 +83,10 @@ func TestSanitizedPathJoin(t *testing.T) {
 			expect:    filepath.Join("C:\\www", "foo", "bar"),
 		},
 		{
-			inputRoot: "C:\\www",
-			inputPath: "/D:\\foo\\bar",
-			expect:    filepath.Join("C:\\www", "D:\\foo\\bar"),
+			inputRoot:     "C:\\www",
+			inputPath:     "/D:\\foo\\bar",
+			expect:        filepath.Join("C:\\www", "D:\\foo\\bar"),
+			expectWindows: filepath.Join("C:\\www"),
 		},
 		{
 			// https://github.com/golang/go/issues/56336#issuecomment-1416214885
@@ -102,6 +105,9 @@ func TestSanitizedPathJoin(t *testing.T) {
 			t.Fatalf("Test %d: invalid URL: %v", i, err)
 		}
 		actual := SanitizedPathJoin(tc.inputRoot, u.Path)
+		if runtime.GOOS == "windows" && tc.expectWindows != "" {
+			tc.expect = tc.expectWindows
+		}
 		if actual != tc.expect {
 			t.Errorf("Test %d: SanitizedPathJoin('%s', '%s') =>  '%s' (expected '%s')",
 				i, tc.inputRoot, tc.inputPath, actual, tc.expect)