Use proxy-agent to support $HTTP_PROXY

Closes #124

This works by monkey patching the http and https modules's default agent
at runtime to the one given by the proxy-agent package.

src/node/entry.ts

@@ -20,6 +20,7 @@ import { commit, version } from "./constants"
 import { register } from "./routes"
 import { humanPath, isFile, open } from "./util"
 import { isChild, wrapper } from "./wrapper"
+import * as proxyAgent from "./proxy_agent"
 
 export const runVsCodeCli = (args: DefaultedArgs): void => {
   logger.debug("forking vs code cli...")
@@ -154,6 +155,8 @@ const main = async (args: DefaultedArgs): Promise<void> => {
 }
 
 async function entry(): Promise<void> {
+  proxyAgent.monkeyPatch(false)
+
   // There's no need to check flags like --help or to spawn in an existing
   // instance for the child process because these would have already happened in
   // the parent and the child wouldn't have been spawned. We also get the

src/node/proxy_agent.ts

@@ -0,0 +1,45 @@
+import { logger } from "@coder/logger"
+import * as proxyagent from "proxy-agent"
+import * as http from "http"
+
+/**
+ * This file does not have anything to do with the code-server proxy.
+ * It's for $HTTP_PROXY support!
+ * - https://github.com/cdr/code-server/issues/124
+ * - https://www.npmjs.com/package/proxy-agent
+ *
+ * This file exists in two locations:
+ * - src/node/proxy_agent.ts
+ * - lib/vscode/src/vs/base/node/proxy_agent.ts
+ * The second is a symlink to the first.
+ */
+
+/**
+ * monkeyPatch patches the node HTTP/HTTPS library to route all requests through our
+ * custom agent from the proxyAgent package.
+ */
+export function monkeyPatch(vscode: boolean): void {
+  if (!process.env.HTTP_PROXY) {
+    return
+  }
+
+  logger.debug(`using $HTTP_PROXY ${process.env.HTTP_PROXY}`)
+
+  let pa: http.Agent
+  // The reasoning for this split is that VS Code's build process does not have
+  // esModuleInterop enabled but the code-server one does. As a result depending on where
+  // we execute, we either have a default attribute or we don't.
+  //
+  // I can't enable esModuleInterop in VS Code's build process as it breaks and spits out
+  // a huge number of errors.
+  if (vscode) {
+    pa = new (proxyagent as any)(process.env.HTTP_PROXY)
+  } else {
+    pa = new (proxyagent as any).default(process.env.HTTP_PROXY)
+  }
+
+  const http = require("http")
+  const https = require("https")
+  http.globalAgent = pa
+  https.globalAgent = pa
+}