Add --socket-fd CLI option (#7940)

src/node/app.ts

@@ -13,7 +13,8 @@ import { EditorSessionManager, makeEditorSessionManagerServer } from "./vscodeSo
 import { handleUpgrade } from "./wsRouter"
 
 type SocketOptions = { socket: string; "socket-mode"?: string }
-type ListenOptions = DefaultedArgs | SocketOptions
+type FdOptions = { "socket-fd": number }
+type ListenOptions = DefaultedArgs | SocketOptions | FdOptions
 
 export interface App extends Disposable {
   /** Handles regular HTTP requests. */
@@ -30,8 +31,12 @@ const isSocketOpts = (opts: ListenOptions): opts is SocketOptions => {
   return !!(opts as SocketOptions).socket || !(opts as DefaultedArgs).host
 }
 
+export const isFdOpts = (opts: ListenOptions): opts is FdOptions => {
+  return typeof (opts as FdOptions)["socket-fd"] === "number"
+}
+
 export const listen = async (server: http.Server, opts: ListenOptions) => {
-  if (isSocketOpts(opts)) {
+  if (!isFdOpts(opts) && isSocketOpts(opts)) {
     try {
       await fs.unlink(opts.socket)
     } catch (error: any) {
@@ -46,7 +51,9 @@ export const listen = async (server: http.Server, opts: ListenOptions) => {
       server.on("error", (err) => util.logError(logger, "http server error", err))
       resolve()
     }
-    if (isSocketOpts(opts)) {
+    if (isFdOpts(opts)) {
+      server.listen({ fd: opts["socket-fd"] }, onListen)
+    } else if (isSocketOpts(opts)) {
       server.listen(opts.socket, onListen)
     } else {
       // [] is the correct format when using :: but Node errors with them.
@@ -56,7 +63,7 @@ export const listen = async (server: http.Server, opts: ListenOptions) => {
 
   // NOTE@jsjoeio: we need to chmod after the server is finished
   // listening. Otherwise, the socket may not have been created yet.
-  if (isSocketOpts(opts)) {
+  if (!isFdOpts(opts) && isSocketOpts(opts)) {
     if (opts["socket-mode"]) {
       await fs.chmod(opts.socket, opts["socket-mode"])
     }

src/node/cli.ts

@@ -83,6 +83,7 @@ export interface UserProvidedArgs extends UserProvidedCodeArgs {
   open?: boolean
   "bind-addr"?: string
   socket?: string
+  "socket-fd"?: number
   "socket-mode"?: string
   "trusted-origins"?: string[]
   version?: boolean
@@ -236,6 +237,10 @@ export const options: Options<Required<UserProvidedArgs>> = {
   port: { type: "number", description: "" },
 
   socket: { type: "string", path: true, description: "Path to a socket (bind-addr will be ignored)." },
+  "socket-fd": {
+    type: "number",
+    description: "File descriptor of a pre-bound, listening socket to use (for systemd socket activation).",
+  },
   "socket-mode": { type: "string", description: "File mode of the socket." },
   "trusted-origins": {
     type: "string[]",