handle missing version and 'current' as version

.vuepress/enhanceApp.js

@@ -0,0 +1,41 @@
+export default ({
+  Vue, // the version of Vue being used in the VuePress app
+  options, // the options for the root Vue instance
+  router, // the router instance for the app
+  siteData, // site metadata
+  isServer // is this enhancement applied in server-rendering or client
+}) => {
+  findVersionedPaths(siteData.themeConfig.sidebar).forEach(vp => {
+    router.addRoutes(
+      router.options.routes.map(route => {
+        if (route.path.startsWith(vp.path + vp.currentVersion)) {
+          return [
+            {
+              path: route.path.replace(vp.currentVersion, "current"),
+              redirect: route.path
+            }, {
+              path: route.path.replace(vp.currentVersion + "/", ""),
+              redirect: route.path
+            }
+          ]
+        }
+        return undefined
+      }).filter(x => x).flat()
+    )
+  })
+}
+
+function findVersionedPaths(paths) {
+  return Object.entries(paths).map(([path, children]) => {
+    return children
+      .filter(child => Array.isArray(child.versions))
+      .map(child => ({ ...child, path: pathJoin(path, child.path) }))
+  }).flat()
+}
+
+// https://stackoverflow.com/a/29855282/4430124
+function pathJoin(...parts) {
+  var separator = '/';
+  var replace = new RegExp(separator + '{1,}', 'g');
+  return parts.join(separator).replace(replace, separator);
+}