refactor: remove the features option (#2410)

BREAKING CHANGE: the `features` option was remove without alternatives

Author: evilebottnawi

lib/Server.js

@@ -557,7 +557,7 @@ class Server {
       runnableFeatures.push('after');
     }
 
-    (this.options.features || runnableFeatures).forEach((feature) => {
+    runnableFeatures.forEach((feature) => {
       features[feature]();
     });
   }

lib/options.json

@@ -68,12 +68,6 @@
     "disableHostCheck": {
       "type": "boolean"
     },
-    "features": {
-      "type": "array",
-      "items": {
-        "type": "string"
-      }
-    },
     "filename": {
       "anyOf": [
         {
@@ -424,7 +418,6 @@
       "compress": "should be {Boolean} (https://webpack.js.org/configuration/dev-server/#devservercompress)",
       "contentBase": "should be {Number|String|Array} (https://webpack.js.org/configuration/dev-server/#devservercontentbase)",
       "disableHostCheck": "should be {Boolean} (https://webpack.js.org/configuration/dev-server/#devserverdisablehostcheck)",
-      "features": "should be {Array}",
       "filename": "should be {String|RegExp|Function} (https://webpack.js.org/configuration/dev-server/#devserverfilename-)",
       "fs": "should be {Object} (https://github.com/webpack/webpack-dev-middleware#fs)",
       "headers": "should be {Object} (https://webpack.js.org/configuration/dev-server/#devserverheaders-)",

test/__snapshots__/validate-options.test.js.snap

@@ -82,12 +82,6 @@ exports[`options should throw an error on the "disableHostCheck" option with ""
  - options.disableHostCheck should be a boolean."
 `;
 
-exports[`options should throw an error on the "features" option with "false" value 1`] = `
-"Invalid options object. Dev Server has been initialized using an options object that does not match the API schema.
- - options.features should be an array:
-   [string, ...]"
-`;
-
 exports[`options should throw an error on the "filename" option with "false" value 1`] = `
 "Invalid options object. Dev Server has been initialized using an options object that does not match the API schema.
  - options.filename should be one of these:

test/validate-options.test.js

@@ -67,10 +67,6 @@ describe('options', () => {
       success: [true],
       failure: [''],
     },
-    features: {
-      success: [['before'], []],
-      failure: [false],
-    },
     filename: {
       success: ['', new RegExp(''), () => {}],
       failure: [false],