refactor(typescript): convert proxy to typescript (#4878)

lib/proxy.js → lib/proxy.ts

-const { createGlobalProxyAgent } = require('global-agent');
-
-module.exports = {
-  bootstrap,
-};
+import {
+  createGlobalProxyAgent,
+  ProxyAgentConfigurationType,
+} from 'global-agent';
 
 const envVars = ['HTTP_PROXY', 'HTTPS_PROXY', 'NO_PROXY'];
 
-function bootstrap() {
+export function bootstrap(): ProxyAgentConfigurationType {
   envVars.forEach(envVar => {
+    /* istanbul ignore if: env is case-insensitive on windows */
     if (
       typeof process.env[envVar] === 'undefined' &&
       typeof process.env[envVar.toLowerCase()] !== 'undefined'

lib/types/global-agent.d.ts

+declare module 'global-agent' {
+  export interface ProxyAgentConfigurationInputType {
+    environmentVariableNamespace?: string;
+    forceGlobalAgent?: boolean;
+    socketConnectionTimeout?: number;
+  }
+
+  export interface ProxyAgentConfigurationType {
+    readonly HTTP_PROXY: string;
+    readonly HTTPS_PROXY: string;
+    readonly NO_PROXY: string;
+  }
+
+  export function createGlobalProxyAgent(
+    opts: ProxyAgentConfigurationInputType
+  ): ProxyAgentConfigurationType;
+}

test/proxy.spec.ts

@@ -5,6 +5,13 @@ describe('proxy', () => {
   const httpsProxy = 'http://example.org/https-proxy';
   const noProxy = 'http://example.org/no-proxy';
 
+  beforeAll(() => {
+    delete process.env.HTTP_PROXY;
+    delete process.env.HTTPS_PROXY;
+    delete process.env.NO_PROXY;
+    delete process.env.no_proxy;
+  });
+
   it('respects HTTP_PROXY', () => {
     process.env.HTTP_PROXY = httpProxy;
     const result = bootstrap();
@@ -15,8 +22,8 @@ describe('proxy', () => {
     const result = bootstrap();
     expect(result.HTTPS_PROXY).toEqual(httpsProxy);
   });
-  it('respects NO_PROXY', () => {
-    process.env.NO_PROXY = noProxy;
+  it('respects no_proxy', () => {
+    process.env.no_proxy = noProxy;
     const result = bootstrap();
     expect(result.NO_PROXY).toEqual(noProxy);
   });