fix: promise support in config

packages/webpack-cli/lib/groups/ConfigGroup.js

@@ -86,7 +86,7 @@ class ConfigGroup extends GroupHelper {
         };
     }
 
-    finalize(moduleObj) {
+    async finalize(moduleObj) {
         const newOptionsObject = {
             outputOptions: {},
             options: {},
@@ -100,7 +100,8 @@ class ConfigGroup extends GroupHelper {
         if (typeof configOptions === 'function') {
             // when config is a function, pass the env from args to the config function
             const newOptions = configOptions(this.args.env);
-            newOptionsObject['options'] = newOptions;
+            // When config function returns a promise, resolve it, if not it's resolved by default
+            newOptionsObject['options'] = await Promise.resolve(newOptions);
         } else {
             if (Array.isArray(configOptions) && !configOptions.length) {
                 newOptionsObject['options'] = {};
@@ -124,7 +125,7 @@ class ConfigGroup extends GroupHelper {
         return newOptionsObject;
     }
 
-    resolveConfigFiles() {
+    async resolveConfigFiles() {
         const { config, mode } = this.args;
 
         if (config) {
@@ -139,7 +140,7 @@ class ConfigGroup extends GroupHelper {
             }
             const foundConfig = configFiles[0];
             const resolvedConfig = this.requireConfig(foundConfig);
-            this.opts = this.finalize(resolvedConfig);
+            this.opts = await this.finalize(resolvedConfig);
             return;
         }
 
@@ -152,16 +153,16 @@ class ConfigGroup extends GroupHelper {
         if (configFiles.length) {
             const defaultConfig = configFiles.find((p) => p.path.includes(mode) || p.path.includes(modeAlias[mode]));
             if (defaultConfig) {
-                this.opts = this.finalize(defaultConfig);
+                this.opts = await this.finalize(defaultConfig);
                 return;
             }
             const foundConfig = configFiles.pop();
-            this.opts = this.finalize(foundConfig);
+            this.opts = await this.finalize(foundConfig);
             return;
         }
     }
 
-    resolveConfigMerging() {
+    async resolveConfigMerging() {
         // eslint-disable-next-line no-prototype-builtins
         if (Object.keys(this.args).some((arg) => arg === 'merge')) {
             const { merge } = this.args;
@@ -178,16 +179,16 @@ class ConfigGroup extends GroupHelper {
                 }
                 const foundConfig = configFiles[0];
                 const resolvedConfig = this.requireConfig(foundConfig);
-                const newConfigurationsObject = this.finalize(resolvedConfig);
+                const newConfigurationsObject = await this.finalize(resolvedConfig);
                 const webpackMerge = require('webpack-merge');
                 this.opts['options'] = webpackMerge(this.opts['options'], newConfigurationsObject.options);
             }
         }
     }
 
-    run() {
-        this.resolveConfigFiles();
-        this.resolveConfigMerging();
+    async run() {
+        await this.resolveConfigFiles();
+        await this.resolveConfigMerging();
         return this.opts;
     }
 }

packages/webpack-cli/lib/webpack-cli.js

@@ -185,9 +185,9 @@ class WebpackCLI extends GroupHelper {
      * @private
      * @returns {void}
      */
-    _handleGroupHelper(groupHelper) {
+    async _handleGroupHelper(groupHelper) {
         if (groupHelper) {
-            const result = groupHelper.run();
+            const result = await groupHelper.run();
             this._mergeOptionsToConfiguration(result.options, groupHelper.strategy);
             this._mergeOptionsToOutputConfiguration(result.outputOptions);
             this._mergeProcessingMessageBuffer(result.processingMessageBuffer);

test/config/type/promise/promise-config.test.js

@@ -1,18 +1,13 @@
 'use strict';
 const { stat } = require('fs');
-const { resolve, sep } = require('path');
-const { run, extractSummary } = require('../../../utils/test-utils');
+const { resolve } = require('path');
+const { run } = require('../../../utils/test-utils');
 
 describe('promise configuration', () => {
-    it.skip('is able to understand a configuration file as a promise', (done) => {
-        const { stdout } = run(__dirname, ['-c', resolve(__dirname, 'webpack.config.js')], false);
-        const summary = extractSummary(stdout);
-        const outputDir = 'type/promise/binary';
-        const outDirectoryFromCompiler = summary['Output Directory'].split(sep);
-        const outDirToMatch = outDirectoryFromCompiler
-            .slice(outDirectoryFromCompiler.length - 3, outDirectoryFromCompiler.length)
-            .join('/');
-        expect(outDirToMatch).toContain(outputDir);
+    it('is able to understand a configuration file as a promise', (done) => {
+        const { stdout, stderr } = run(__dirname, ['-c', './webpack.config.js'], false);
+        expect(stdout).toBeTruthy();
+        expect(stderr).toBeFalsy();
         stat(resolve(__dirname, './binary/promise.js'), (err, stats) => {
             expect(err).toBe(null);
             expect(stats.isFile()).toBe(true);