v2: Make tests work on Windows (#2782)

* file_server: Make tests work on Windows

* caddyfile: Fix escaping when character is not escapable

We only escape certain characters depending on inside or outside of
quotes (mainly newlines and quotes). We don't want everyone to have to
escape Windows file paths like C:\\Windows\\... but we can't drop the
\ either if it's just C:\Windows\...

caddyconfig/caddyfile/lexer.go

@@ -153,6 +153,11 @@ func (l *lexer) next() bool {
 			}
 		}
 
+		if escaped {
+			val = append(val, '\\')
+			escaped = false
+		}
+
 		val = append(val, ch)
 	}
 }

caddyconfig/caddyfile/lexer_test.go

@@ -151,6 +151,12 @@ func TestLexer(t *testing.T) {
 				{Line: 1, Text: `don't\\escape`},
 			},
 		},
+		{
+			input: `un\escapable`,
+			expected: []Token{
+				{Line: 1, Text: `un\escapable`},
+			},
+		},
 		{
 			input: `A "quoted value with line
 					break inside" {

modules/caddyhttp/fileserver/staticfiles_test.go

@@ -16,14 +16,15 @@ package fileserver
 
 import (
 	"net/url"
+	"path/filepath"
 	"testing"
 )
 
 func TestSanitizedPathJoin(t *testing.T) {
 	// For easy reference:
-	// %2E = .
-	// %2F = /
-	// %5C = \
+	// %2e = .
+	// %2f = /
+	// %5c = \
 	for i, tc := range []struct {
 		inputRoot string
 		inputPath string
@@ -43,12 +44,12 @@ func TestSanitizedPathJoin(t *testing.T) {
 		},
 		{
 			inputPath: "/foo/bar",
-			expect:    "foo/bar",
+			expect:    filepath.Join("foo", "bar"),
 		},
 		{
 			inputRoot: "/a",
 			inputPath: "/foo/bar",
-			expect:    "/a/foo/bar",
+			expect:    filepath.Join("/", "a", "foo", "bar"),
 		},
 		{
 			inputPath: "/foo/../bar",
@@ -57,24 +58,29 @@ func TestSanitizedPathJoin(t *testing.T) {
 		{
 			inputRoot: "/a/b",
 			inputPath: "/foo/../bar",
-			expect:    "/a/b/bar",
+			expect:    filepath.Join("/", "a", "b", "bar"),
 		},
 		{
 			inputRoot: "/a/b",
 			inputPath: "/..%2fbar",
-			expect:    "/a/b/bar",
+			expect:    filepath.Join("/", "a", "b", "bar"),
 		},
 		{
 			inputRoot: "/a/b",
 			inputPath: "/%2e%2e%2fbar",
-			expect:    "/a/b/bar",
+			expect:    filepath.Join("/", "a", "b", "bar"),
 		},
 		{
 			inputRoot: "/a/b",
 			inputPath: "/%2e%2e%2f%2e%2e%2f",
-			expect:    "/a/b",
+			expect:    filepath.Join("/", "a", "b"),
 		},
-		// TODO: test windows paths... on windows... sigh.
+		{
+			inputRoot: "C:\\www",
+			inputPath: "/foo/bar",
+			expect:    filepath.Join("C:\\www", "foo", "bar"),
+		},
+		// TODO: test more windows paths... on windows... sigh.
 	} {
 		// we don't *need* to use an actual parsed URL, but it
 		// adds some authenticity to the tests since real-world