feat(webpack-dev-server): add WEBPACK_DEV_SERVER environment variable

bin/webpack-dev-server.js

@@ -92,6 +92,8 @@ yargs.options(options);
 
 const argv = yargs.argv;
 
+process.env.WEBPACK_DEV_SERVER = true;
+
 // [email protected] path : 'webpack-cli/bin/utils/convert-argv'
 let convertArgvPath;
 try {

lib/Server.js

@@ -90,6 +90,8 @@ class Server {
       throw new Error("'filename' option must be set in lazy mode.");
     }
 
+    process.env.WEBPACK_DEV_SERVER = true;
+
     // if the user enables http2, we can safely enable https
     if (options.http2 && !options.https) {
       options.https = true;

test/Server.test.js

@@ -8,6 +8,13 @@ const config = require('./fixtures/simple-config/webpack.config');
 const helper = require('./helper');
 
 describe('Server', () => {
+  it('process.env.WEBPACK_DEV_SERVER', () => {
+    const compiler = webpack(config);
+    // eslint-disable-next-line no-new
+    new Server(compiler);
+    expect(process.env.WEBPACK_DEV_SERVER).toBeTruthy();
+  });
+
   describe('addEntries', () => {
     it('add hot option', () => {
       return new Promise((res) => {

test/cli.test.js

@@ -17,6 +17,15 @@ const keyPath = path.join(httpsCertificateDirectory, 'server.key');
 const certPath = path.join(httpsCertificateDirectory, 'server.crt');
 
 describe('CLI', () => {
+  it('process.env.WEBPACK_DEV_SERVER', (done) => {
+    runDevServer()
+      .then(() => {
+        expect(process.env.WEBPACK_DEV_SERVER).toBeTruthy();
+        done();
+      })
+      .catch(done);
+  });
+
   it('--progress', (done) => {
     runDevServer('--progress')
       .then((output) => {