feat: adding no_proxy (and NO_PROXY) environment variable support (#28)

It is following the [convention of `curl`](curl/curl#1208 (comment))
 regarding no_proxy

Author: ArchangelX360

src/http.ts

@@ -236,7 +236,7 @@ export class HTTP<T> {
     this.options.protocol = u.protocol || this.options.protocol
     this.options.host = u.hostname || this.ctor.defaults.host || 'localhost'
     this.options.path = u.path || '/'
-    this.options.agent = this.options.agent || deps.proxy.agent(this.secure)
+    this.options.agent = this.options.agent || deps.proxy.agent(this.secure, this.options.host)
     this.options.port = u.port || this.options.port || (this.secure ? 443 : 80)
   }
   get headers(): http.IncomingMessage['headers'] {

src/proxy.test.ts

@@ -73,3 +73,81 @@ describe('with http proxy only', () => {
     })
   })
 })
+
+describe('with no_proxy', () => {
+  beforeEach(() => {
+    Proxy.env.HTTP_PROXY = 'http://user:[email protected]'
+    Proxy.env.NO_PROXY = 'some.com,test-domain.com'
+  })
+
+  test('is an exact match of no_proxy', () => {
+    expect(Proxy.agent(false, 'test-domain.com')).toBeUndefined()
+  })
+
+  test('is a subdomain of no_proxy', () => {
+    expect(Proxy.agent(false, 'something.prod.test-domain.com')).toBeUndefined()
+  })
+
+  test('should be proxied', () => {
+    expect(Proxy.agent(false, 'proxied-domain.com')).toMatchObject({
+      options: {
+        proxy: {
+          host: 'foo.com',
+          port: '8080',
+          proxyAuth: 'user:pass',
+        },
+      },
+      proxyOptions: {
+        host: 'foo.com',
+        port: '8080',
+        proxyAuth: 'user:pass',
+      },
+    })
+  })
+})
+
+describe('proxy dodging', () => {
+  test('not set should proxy', () => {
+    Proxy.env.NO_PROXY = ''
+    expect(Proxy.shouldDodgeProxy('test-domain.com')).toBe(false)
+    expect(Proxy.shouldDodgeProxy('other-domain.com')).toBe(false)
+  })
+
+  test('wildcard proxies any', () => {
+    Proxy.env.NO_PROXY = '*'
+    expect(Proxy.shouldDodgeProxy('test-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('anything.other-domain.com')).toBe(true)
+  })
+
+  test('exact domain should also match subdomains', () => {
+    Proxy.env.NO_PROXY = 'test-domain.com'
+    expect(Proxy.shouldDodgeProxy('test-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('anything.test-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('other-domain.com')).toBe(false)
+    expect(Proxy.shouldDodgeProxy('anything.other-domain.com')).toBe(false)
+  })
+
+  test('any sub domain should include the domain itself', () => {
+    Proxy.env.NO_PROXY = '.test-domain.com'
+    expect(Proxy.shouldDodgeProxy('test-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('anything.test-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('other-domain.com')).toBe(false)
+    expect(Proxy.shouldDodgeProxy('anything.other-domain.com')).toBe(false)
+  })
+
+  test('multiple domains', () => {
+    Proxy.env.NO_PROXY = '.test-domain.com, .other-domain.com'
+    expect(Proxy.shouldDodgeProxy('test-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('anything.test-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('other-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('anything.other-domain.com')).toBe(true)
+  })
+
+  test('match any subdomains', () => {
+    Proxy.env.NO_PROXY = '.test-domain.com, other-domain.com'
+    expect(Proxy.shouldDodgeProxy('test-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('something.something-else.anything.test-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('other-domain.com')).toBe(true)
+    expect(Proxy.shouldDodgeProxy('something.anything.other-domain.com')).toBe(true)
+  })
+})

src/proxy.ts

@@ -20,7 +20,22 @@ export default class ProxyUtil {
     return this.env.HTTPS_PROXY || this.env.https_proxy
   }
 
-  static get usingProxy(): boolean {
+  static get noProxy() {
+    return this.env.NO_PROXY || this.env.no_proxy
+  }
+
+  static shouldDodgeProxy(host: string): boolean {
+    if (!this.noProxy) return false
+    if (this.noProxy === '*') return true
+
+    return this.noProxy
+        .split(',')
+        .map(p => p.trim())
+        .some(p => (p[0] === '.' && host.endsWith(p.substr(1))) || host.endsWith(p))
+  }
+
+  static usingProxy(host?: string): boolean {
+    if (host && this.shouldDodgeProxy(host)) return false
     if (this.httpProxy || this.httpsProxy) return true
     return false
   }
@@ -45,8 +60,8 @@ export default class ProxyUtil {
     return filenames.map((filename): Buffer => fs.readFileSync(filename))
   }
 
-  static agent(https: boolean): any {
-    if (!this.usingProxy) return
+  static agent(https: boolean, host?: string): any {
+    if (!this.usingProxy(host)) return
     const u = https ? this.httpsProxy || this.httpProxy : this.httpProxy
     if (u) {
       let proxyParsed = uri.parse(u)