Fix issues surrounding initial web server load. (#4509)

- Clean up watcher behaviors.

src/node/util.ts

@@ -3,14 +3,15 @@ import * as argon2 from "argon2"
 import * as cp from "child_process"
 import * as crypto from "crypto"
 import envPaths from "env-paths"
-import { promises as fs } from "fs"
+import { promises as fs, Stats } from "fs"
 import * as net from "net"
 import * as os from "os"
 import * as path from "path"
 import safeCompare from "safe-compare"
 import * as util from "util"
 import xdgBasedir from "xdg-basedir"
-import { vsRootPath } from "./constants"
+import { logError } from "../common/util"
+import { isDevMode, rootPath, vsRootPath } from "./constants"
 
 export interface Paths {
   data: string
@@ -25,10 +26,11 @@ const pattern = [
 ].join("|")
 const re = new RegExp(pattern, "g")
 
+export type OnLineCallback = (strippedLine: string, originalLine: string) => void
 /**
  * Split stdout on newlines and strip ANSI codes.
  */
-export const onLine = (proc: cp.ChildProcess, callback: (strippedLine: string, originalLine: string) => void): void => {
+export const onLine = (proc: cp.ChildProcess, callback: OnLineCallback): void => {
   let buffer = ""
   if (!proc.stdout) {
     throw new Error("no stdout")
@@ -521,3 +523,41 @@ export const loadAMDModule = async <T>(amdPath: string, exportName: string): Pro
 
   return module[exportName] as T
 }
+
+export const enum VSCodeCompileStatus {
+  Loading = "Loading",
+  Compiling = "Compiling",
+  Compiled = "Compiled",
+}
+
+export interface CompilationStats {
+  status: VSCodeCompileStatus
+  lastCompiledAt: Date
+}
+
+export const readCompilationStats = async (): Promise<null | CompilationStats> => {
+  if (!isDevMode) {
+    throw new Error("Compilation stats are only present in development")
+  }
+
+  const filePath = path.join(rootPath, "out/watcher.json")
+  let stat: Stats
+  try {
+    stat = await fs.stat(filePath)
+  } catch (error) {
+    return null
+  }
+
+  if (!stat.isFile()) {
+    return null
+  }
+
+  try {
+    const file = await fs.readFile(filePath)
+    return JSON.parse(file.toString("utf-8"))
+  } catch (error) {
+    logError(logger, "VS Code", error)
+  }
+
+  return null
+}