Accept undefined and null in plugins

declarations/WebpackOptions.d.ts

@@ -596,7 +596,7 @@ export type Performance = false | PerformanceOptions;
 /**
  * Add additional plugins to the compiler.
  */
-export type Plugins = (WebpackPluginInstance | WebpackPluginFunction)[];
+export type Plugins = (null | WebpackPluginInstance | WebpackPluginFunction)[];
 /**
  * Capture timing information for each module.
  */

lib/Compiler.js

@@ -1073,7 +1073,9 @@ ${other}`);
 		childCompiler.root = this.root;
 		if (Array.isArray(plugins)) {
 			for (const plugin of plugins) {
-				plugin.apply(childCompiler);
+				if ("apply" in plugin) {
+					plugin.apply(childCompiler);
+				}
 			}
 		}
 		for (const name in this.hooks) {

lib/rules/RuleSetCompiler.js

@@ -54,7 +54,9 @@ class RuleSetCompiler {
 		});
 		if (plugins) {
 			for (const plugin of plugins) {
-				plugin.apply(this);
+				if ("apply" in plugin) {
+					plugin.apply(this);
+				}
 			}
 		}
 	}

lib/webpack.js

@@ -69,7 +69,7 @@ const createCompiler = rawOptions => {
 		for (const plugin of options.plugins) {
 			if (typeof plugin === "function") {
 				plugin.call(compiler, compiler);
-			} else {
+			} else if ("apply" in plugin) {
 				plugin.apply(compiler);
 			}
 		}

schemas/WebpackOptions.json

@@ -3561,6 +3561,9 @@
       "items": {
         "description": "Plugin of type object or instanceof Function.",
         "anyOf": [
+          {
+            "type": "null"
+          },
           {
             "$ref": "#/definitions/WebpackPluginInstance"
           },

test/Validation.test.js

@@ -315,9 +315,10 @@ describe("Validation", () => {
 			expect(msg).toMatchInlineSnapshot(`
 			"Invalid configuration object. Webpack has been initialized using a configuration object that does not match the API schema.
 			 - configuration.plugins[0] should be one of these:
-			   object { apply, … } | function
+			   null | object { apply, … } | function
 			   -> Plugin of type object or instanceof Function.
 			   Details:
+			    * configuration.plugins[0] should be a null.
 			    * configuration.plugins[0] should be an object:
 			      object { apply, … }
 			      -> Plugin instance.
@@ -336,9 +337,10 @@ describe("Validation", () => {
 			expect(msg).toMatchInlineSnapshot(`
 			"Invalid configuration object. Webpack has been initialized using a configuration object that does not match the API schema.
 			 - configuration.plugins[0] should be one of these:
-			   object { apply, … } | function
+			   null | object { apply, … } | function
 			   -> Plugin of type object or instanceof Function.
 			   Details:
+			    * configuration.plugins[0] should be a null.
 			    * configuration.plugins[0] should be an object:
 			      object { apply, … }
 			      -> Plugin instance.
@@ -357,9 +359,10 @@ describe("Validation", () => {
 			expect(msg).toMatchInlineSnapshot(`
 			"Invalid configuration object. Webpack has been initialized using a configuration object that does not match the API schema.
 			 - configuration.plugins[0] should be one of these:
-			   object { apply, … } | function
+			   null | object { apply, … } | function
 			   -> Plugin of type object or instanceof Function.
 			   Details:
+			    * configuration.plugins[0] should be a null.
 			    * configuration.plugins[0] should be an object:
 			      object { apply, … }
 			      -> Plugin instance.
@@ -378,9 +381,10 @@ describe("Validation", () => {
 			expect(msg).toMatchInlineSnapshot(`
 			"Invalid configuration object. Webpack has been initialized using a configuration object that does not match the API schema.
 			 - configuration.plugins[0] should be one of these:
-			   object { apply, … } | function
+			   null | object { apply, … } | function
 			   -> Plugin of type object or instanceof Function.
 			   Details:
+			    * configuration.plugins[0] should be a null.
 			    * configuration.plugins[0] should be an object:
 			      object { apply, … }
 			      -> Plugin instance.

test/configCases/plugins/null-undefined/index.js

@@ -0,0 +1,3 @@
+it("should accept null and undefined as plugins and define TRUE", function() {
+	expect(TRUE).toBe(true);
+});

test/configCases/plugins/null-undefined/webpack.config.js

@@ -0,0 +1,12 @@
+var DefinePlugin = require("../../../../").DefinePlugin;
+
+/** @type {import("../../../../").Configuration[]} */
+module.exports = {
+	plugins: [
+		null,
+		undefined,
+		new DefinePlugin({
+			TRUE: true
+		})
+	]
+};

types.d.ts

@@ -2378,6 +2378,7 @@ declare interface Configuration {
 	 * Add additional plugins to the compiler.
 	 */
 	plugins?: (
+		| null
 		| ((this: Compiler, compiler: Compiler) => void)
 		| WebpackPluginInstance
 	)[];
@@ -13149,6 +13150,7 @@ declare interface WebpackOptionsNormalized {
 	 * Add additional plugins to the compiler.
 	 */
 	plugins: (
+		| null
 		| ((this: Compiler, compiler: Compiler) => void)
 		| WebpackPluginInstance
 	)[];