Function UpdateAssetsSubpathInDir

server/channels/utils/subpath.go:49–96

UpdateAssetsSubpathInDir rewrites assets in the given directory to assume the application is hosted at the given subpath instead of at the root. No changes are written unless necessary.

(subpath, directory string)

// UpdateAssetsSubpathInDir rewrites assets in the given directory to assume the application is
// hosted at the given subpath instead of at the root. No changes are written unless necessary.
func UpdateAssetsSubpathInDir(subpath, directory string) error {
	if subpath == "" {
		subpath = "/"
	}

	// Resolve the static directory
	staticDir, found := fileutils.FindDir(directory)
	if !found {
		return errors.New("failed to find client dir")
	}
	staticDir, err := filepath.EvalSymlinks(staticDir)
	if err != nil {
		return errors.Wrapf(err, "failed to resolve symlinks to %s", staticDir)
	}

	// Read the old root.html file
	rootHTMLPath := filepath.Join(staticDir, "root.html")
	oldRootHTML, err := os.ReadFile(rootHTMLPath)
	if err != nil {
		return errors.Wrap(err, "failed to open root.html")
	}

	oldSubpath := "/"

	// Determine if a previous subpath had already been rewritten into the assets.
	reWebpackPublicPathScript := regexp.MustCompile("window.publicPath='([^']+/)static/'")
	alreadyRewritten := false
	if matches := reWebpackPublicPathScript.FindStringSubmatch(string(oldRootHTML)); matches != nil {
		oldSubpath = matches[1]
		alreadyRewritten = true
	}

	// Determine the old and new paths
	pathToReplace := path.Join(oldSubpath, "static") + "/"
	newPath := path.Join(subpath, "static") + "/"

	// Update the root.html file
	if err := updateRootFile(string(oldRootHTML), rootHTMLPath, alreadyRewritten, pathToReplace, newPath, subpath); err != nil {
		return fmt.Errorf("failed to update root.html: %w", err)
	}

	// Update the manifest.json and *.css files
	if err := updateManifestAndCSSFiles(staticDir, pathToReplace, newPath, subpath); err != nil {
		return fmt.Errorf("failed to update manifest.json and *.css files: %w", err)
	}

	return nil
}

func updateRootFile(oldRootHTML string, rootHTMLPath string, alreadyRewritten bool, pathToReplace, newPath, subpath string) error {
	newRootHTML := oldRootHTML