Move onMessage so it can be used in the wrappers

src/node/vscode.ts

@@ -1,4 +1,4 @@
-import { field, logger } from "@coder/logger"
+import { logger } from "@coder/logger"
 import * as cp from "child_process"
 import * as net from "net"
 import * as path from "path"
@@ -8,13 +8,12 @@ import { rootPath } from "./constants"
 import { settings } from "./settings"
 import { SocketProxyProvider } from "./socket"
 import { isFile } from "./util"
-import { wrapper } from "./wrapper"
+import { onMessage, wrapper } from "./wrapper"
 
 export class VscodeProvider {
   public readonly serverRootPath: string
   public readonly vsRootPath: string
   private _vscode?: Promise<cp.ChildProcess>
-  private timeoutInterval = 10000 // 10s, matches VS Code's timeouts.
   private readonly socketProvider = new SocketProxyProvider()
 
   public constructor() {
@@ -69,10 +68,13 @@ export class VscodeProvider {
       vscode,
     )
 
-    const message = await this.onMessage(vscode, (message): message is ipc.OptionsMessage => {
+    const message = await onMessage<ipc.VscodeMessage, ipc.OptionsMessage>(
+      vscode,
+      (message): message is ipc.OptionsMessage => {
         // There can be parallel initializations so wait for the right ID.
         return message.type === "options" && message.id === id
-    })
+      },
+    )
 
     return message.options
   }
@@ -104,61 +106,13 @@ export class VscodeProvider {
       dispose()
     })
 
-    this._vscode = this.onMessage(vscode, (message): message is ipc.ReadyMessage => {
+    this._vscode = onMessage<ipc.VscodeMessage, ipc.ReadyMessage>(vscode, (message): message is ipc.ReadyMessage => {
       return message.type === "ready"
     }).then(() => vscode)
 
     return this._vscode
   }
 
-  /**
-   * Listen to a single message from a process. Reject if the process errors,
-   * exits, or times out.
-   *
-   * `fn` is a function that determines whether the message is the one we're
-   * waiting for.
-   */
-  private onMessage<T extends ipc.VscodeMessage>(
-    proc: cp.ChildProcess,
-    fn: (message: ipc.VscodeMessage) => message is T,
-  ): Promise<T> {
-    return new Promise((resolve, reject) => {
-      const cleanup = () => {
-        proc.off("error", onError)
-        proc.off("exit", onExit)
-        proc.off("message", onMessage)
-        clearTimeout(timeout)
-      }
-
-      const timeout = setTimeout(() => {
-        cleanup()
-        reject(new Error("timed out"))
-      }, this.timeoutInterval)
-
-      const onError = (error: Error) => {
-        cleanup()
-        reject(error)
-      }
-
-      const onExit = (code: number | null) => {
-        cleanup()
-        reject(new Error(`VS Code exited unexpectedly with code ${code}`))
-      }
-
-      const onMessage = (message: ipc.VscodeMessage) => {
-        logger.trace("got message from vscode", field("message", message))
-        if (fn(message)) {
-          cleanup()
-          resolve(message)
-        }
-      }
-
-      proc.on("message", onMessage)
-      proc.on("error", onError)
-      proc.on("exit", onExit)
-    })
-  }
-
   /**
    * VS Code expects a raw socket. It will handle all the web socket frames.
    */

src/node/wrapper.ts

@@ -5,6 +5,59 @@ import * as rfs from "rotating-file-stream"
 import { Emitter } from "../common/emitter"
 import { paths } from "./util"
 
+const timeoutInterval = 10000 // 10s, matches VS Code's timeouts.
+
+/**
+ * Listen to a single message from a process. Reject if the process errors,
+ * exits, or times out.
+ *
+ * `fn` is a function that determines whether the message is the one we're
+ * waiting for.
+ */
+export function onMessage<M, T extends M>(
+  proc: cp.ChildProcess | NodeJS.Process,
+  fn: (message: M) => message is T,
+  customLogger?: Logger,
+): Promise<T> {
+  return new Promise((resolve, reject) => {
+    const cleanup = () => {
+      proc.off("error", onError)
+      proc.off("exit", onExit)
+      proc.off("message", onMessage)
+      clearTimeout(timeout)
+    }
+
+    const timeout = setTimeout(() => {
+      cleanup()
+      reject(new Error("timed out"))
+    }, timeoutInterval)
+
+    const onError = (error: Error) => {
+      cleanup()
+      reject(error)
+    }
+
+    const onExit = (code: number) => {
+      cleanup()
+      reject(new Error(`exited unexpectedly with code ${code}`))
+    }
+
+    const onMessage = (message: M) => {
+      ;(customLogger || logger).trace("got message", field("message", message))
+      if (fn(message)) {
+        cleanup()
+        resolve(message)
+      }
+    }
+
+    proc.on("message", onMessage)
+    // NodeJS.Process doesn't have `error` but binding anyway shouldn't break
+    // anything. It does have `exit` but the types aren't working.
+    ;(proc as cp.ChildProcess).on("error", onError)
+    ;(proc as cp.ChildProcess).on("exit", onExit)
+  })
+}
+
 interface HandshakeMessage {
   type: "handshake"
 }
@@ -111,19 +164,15 @@ class ChildProcess extends Process {
   /**
    * Initiate the handshake and wait for a response from the parent.
    */
-  public handshake(): Promise<void> {
+  public async handshake(): Promise<void> {
-    return new Promise((resolve) => {
-      const onMessage = (message: Message): void => {
-        logger.debug(`received message from ${this.parentPid}`, field("message", message))
-        if (message.type === "handshake") {
-          process.removeListener("message", onMessage)
-          resolve()
-        }
-      }
-      // Initiate the handshake and wait for the reply.
-      process.on("message", onMessage)
     this.send({ type: "handshake" })
-    })
+    await onMessage<Message, HandshakeMessage>(
+      process,
+      (message): message is HandshakeMessage => {
+        return message.type === "handshake"
+      },
+      this.logger,
+    )
   }
 
   /**
@@ -270,23 +319,15 @@ export class ParentProcess extends Process {
   /**
    * Wait for a handshake from the child then reply.
    */
-  private handshake(child: cp.ChildProcess): Promise<void> {
+  private async handshake(child: cp.ChildProcess): Promise<void> {
-    return new Promise((resolve, reject) => {
+    await onMessage<Message, HandshakeMessage>(
-      const onMessage = (message: Message): void => {
+      child,
-        logger.debug(`received message from ${child.pid}`, field("message", message))
+      (message): message is HandshakeMessage => {
-        if (message.type === "handshake") {
+        return message.type === "handshake"
-          child.removeListener("message", onMessage)
+      },
-          child.on("message", (msg) => this._onChildMessage.emit(msg))
+      this.logger,
+    )
     child.send({ type: "handshake" })
-          resolve()
-        }
-      }
-      child.on("message", onMessage)
-      child.once("error", reject)
-      child.once("exit", (code) => {
-        reject(new ProcessError(`Unexpected exit with code ${code}`, code !== null ? code : undefined))
-      })
-    })
   }
 }