Default the session socket to a named pipe on windows

src/node/cli.ts

@@ -1,4 +1,5 @@
 import { field, Level, logger } from "@coder/logger"
+import * as crypto from "crypto"
 import { promises as fs } from "fs"
 import { load } from "js-yaml"
 import * as path from "path"
@@ -561,7 +562,7 @@ export async function setDefaults(cliArgs: UserProvidedArgs, configArgs?: Config
   }
 
   if (!args["session-socket"]) {
-    args["session-socket"] = path.join(args["user-data-dir"], "code-server-ipc.sock")
+    args["session-socket"] = defaultSessionSocket(args["user-data-dir"])
   }
   process.env.CODE_SERVER_SESSION_SOCKET = args["session-socket"]
 
@@ -710,6 +711,25 @@ export async function setDefaults(cliArgs: UserProvidedArgs, configArgs?: Config
   } as DefaultedArgs // TODO: Technically no guarantee this is fulfilled.
 }
 
+/**
+ * The session socket to use when one was not given.
+ *
+ * Windows has no Unix sockets, so there it is a named pipe, which lives in its
+ * own namespace rather than on disk and so cannot be placed inside the user
+ * data directory. The name is derived from that directory anyway, so that two
+ * instances with separate data directories do not collide and a later
+ * invocation with the same one finds the first. Windows paths are compared
+ * without regard to case, so the name is folded before it is hashed; otherwise
+ * the same directory typed two ways would produce two pipes.
+ */
+export function defaultSessionSocket(userDataDir: string, platform: NodeJS.Platform = process.platform): string {
+  if (platform !== "win32") {
+    return path.join(userDataDir, "code-server-ipc.sock")
+  }
+  const name = crypto.createHash("sha256").update(path.resolve(userDataDir).toLowerCase()).digest("hex").slice(0, 16)
+  return String.raw`\\.\pipe\code-server-ipc-${name}`
+}
+
 export function getResolvedPathsFromArgs(args: UserProvidedArgs): string[] {
   return (args._ ?? []).map((p) => path.resolve(p))
 }

test/unit/node/cli.test.ts

@@ -5,6 +5,7 @@ import {
   UserProvidedArgs,
   bindAddrFromArgs,
   defaultConfigFile,
+  defaultSessionSocket,
   parse,
   parseConfigFile,
   setDefaults,
@@ -37,7 +38,7 @@ const defaults = {
   usingEnvHashedPassword: false,
   "extensions-dir": path.join(paths.data, "extensions"),
   "user-data-dir": paths.data,
-  "session-socket": path.join(paths.data, "code-server-ipc.sock"),
+  "session-socket": defaultSessionSocket(paths.data),
   "app-name": "code-server",
   _: [],
 }
@@ -977,6 +978,26 @@ describe("bindAddrFromArgs", () => {
   })
 })
 
+describe("defaultSessionSocket", () => {
+  const dataDir = path.join("/home/coder/.local/share", "code-server")
+
+  it("should put the socket in the user data directory", () => {
+    expect(defaultSessionSocket(dataDir, "linux")).toBe(path.join(dataDir, "code-server-ipc.sock"))
+  })
+
+  it("should use a named pipe on windows", () => {
+    expect(defaultSessionSocket(dataDir, "win32")).toMatch(/^\\\\\.\\pipe\\code-server-ipc-[0-9a-f]{16}$/)
+  })
+
+  it("should give separate data directories separate pipes", () => {
+    expect(defaultSessionSocket(dataDir, "win32")).not.toBe(defaultSessionSocket(dataDir + "-other", "win32"))
+  })
+
+  it("should give one data directory one pipe however it is spelled", () => {
+    expect(defaultSessionSocket(dataDir.toUpperCase(), "win32")).toBe(defaultSessionSocket(dataDir, "win32"))
+  })
+})
+
 describe("defaultConfigFile", () => {
   it("should return the default config file as a string", async () => {
     const password = await generatePassword()