Parsing error due to incorrect slashes with embed on windows.

[sedyh]

Problem

Hello, I found a problem in the operation of one of the UnmarshalXML in Map.
This code will cause os.ErrNotExist on windows for data/world/surface-tileset.tmx even if the file is there:

//go:embed data
var fs embed.FS
...
// File surface.tmx has reference to surface-tileset.tmx in it.
tiled.LoadFile("data/world/surface.tmx", tiled.WithFileSystem(fs))

The library allows you to insert your own fs implementation to upload files:
https://github.com/lafriks/go-tiled/blob/main/tiled.go#L76

In the process, it loads additional files (for example, tileset) for which it builds a path as follows:
https://github.com/lafriks/go-tiled/blob/main/tmx_map.go#L173

Which will return the path with windows-like slashes data\world\surface-tileset.tmx. This path will not work with embed:
golang/go#44305

Despite the fact that these are details of the implementation of a specific fs, it is part of the standard library.
So it makes sense to take these details into account inside the lib.

Solution A

Add a wrapper that converts paths in special cases.

func WithFileSystem(fileSystem fs.FS) LoaderOption {
	return func(l *loader) {
		l.FileSystem = fileSystem
		if _, ok := l.FileSystem.(*embed.FS); ok {
			l.FileSystem = WithPathRelative(FileSystem)
		}
	}
}

type PathRelativeFS struct {
	fs fs.FS
}

func WithPathRelative(fs fs.FS) fs.FS {
	return &PathRelativeFS{fs}
}

func (p *PathRelativeFS) Open(name string) (fs.File, error) {
	name = strings.Replace(name, string(filepath.Separator), "/", -1)
	return p.fs.Open(name)
}

Solution B

Add the option to use path.Join instead of filepath.Join for special occasions.

func (m *Map) GetFileFullPath(fileName string) string {
	if _, ok := m.loader.FileSystem.(*embed.FS); ok {
		return path.Join(m.baseDir, fileName)
	}
	return filepath.Join(m.baseDir, fileName)
}

Looks like it the same as #63.

[lafriks]

Looks like duplicate for #63 closing this.

There is also provided better solution for this: tslocum@2d2dec4

imho it is not correct to use path.Join

[lafriks]

feel free to send PR for this

[sedyh]

Thats strange... no one has made a fix for the issue since last year. I'l try, if I have time.

[lafriks]

I have no windows to test on, so I not really want to implement something I'm not able to even test :]