fix: improve error message

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

@@ -940,8 +940,15 @@ class WebpackCLI {
                     const command = findCommandByName(name);
 
                     if (!command) {
-                        this.logger.error(`Can't find and load command '${name}'`);
-                        this.logger.error("Run 'webpack --help' to see available commands and options");
+                        const builtInCommandUsed = externalBuiltInCommandsInfo.find(
+                            (command) => command.name.includes(name) || name === command.alias,
+                        );
+                        if (typeof builtInCommandUsed !== 'undefined') {
+                            this.logger.error(`For using '${name}' command you need to install '${builtInCommandUsed.pkg}' package`);
+                        } else {
+                            this.logger.error(`Can't find and load command '${name}'`);
+                            this.logger.error("Run 'webpack --help' to see available commands and options");
+                        }
                         process.exit(2);
                     }
 

smoketests/index.js

@@ -1,5 +1,9 @@
 /* eslint-disable node/no-unpublished-require */
-const tests = [require('./missing-packages/webpack-dev-server.test.js'), require('./missing-packages/webpack.test.js')];
+const tests = [
+    require('./missing-packages/webpack-dev-server.test.js'),
+    require('./missing-packages/webpack.test.js'),
+    require('./missing-command-help/generator.test.js'),
+];
 
 (async () => {
     let isAllPassed = true;

smoketests/missing-command-help/generator.test.js

@@ -0,0 +1,77 @@
+'use strict';
+
+const path = require('path');
+const execa = require('execa');
+const { renameSync } = require('fs');
+const stripAnsi = require('strip-ansi');
+
+const ROOT = process.env.GITHUB_WORKSPACE ? process.env.GITHUB_WORKSPACE : path.resolve(__dirname, '../../');
+const CLI_ENTRY_PATH = path.resolve(ROOT, './packages/webpack-cli/bin/cli.js');
+
+const getPkgPath = (pkg) => {
+    return path.resolve(ROOT, `./node_modules/@webpack-cli/${pkg}`);
+};
+
+const swapPkgName = (current, next) => {
+    console.log(`  swapping ${current} with ${next}`);
+    renameSync(getPkgPath(current), getPkgPath(next));
+};
+
+const runTest = () => {
+    // Simulate package missing
+    swapPkgName('generators', '.generators');
+
+    const proc = execa(CLI_ENTRY_PATH, ['help', 'init'], {
+        cwd: __dirname,
+    });
+
+    proc.stdin.setDefaultEncoding('utf-8');
+
+    proc.stdout.on('data', (chunk) => {
+        console.log(`  stdout: ${chunk.toString()}`);
+    });
+
+    return new Promise((resolve) => {
+        setTimeout(() => {
+            proc.kill();
+        }, 30000);
+
+        const logMessage = "For using 'init' command you need to install '@webpack-cli/generators' package";
+        const undefinedLogMessage = "Can't find and load command";
+
+        let hasLogMessage = false,
+            hasUndefinedLogMessage = false,
+            hasPassed = false;
+
+        proc.stderr.on('data', (chunk) => {
+            let data = stripAnsi(chunk.toString());
+            console.log(`  stderr: ${data}`);
+
+            if (data.includes(logMessage)) {
+                hasLogMessage = true;
+            }
+
+            if (data.includes(undefinedLogMessage)) {
+                hasUndefinedLogMessage = true;
+            }
+
+            if (hasLogMessage || hasUndefinedLogMessage) {
+                hasPassed = true;
+                proc.kill();
+            }
+        });
+
+        proc.on('exit', () => {
+            swapPkgName('.generators', 'generators');
+            resolve(hasPassed);
+        });
+
+        proc.on('error', () => {
+            swapPkgName('.generators', 'generators');
+            resolve(false);
+        });
+    });
+};
+
+module.exports.run = runTest;
+module.exports.name = 'Missing @webpack-cli/generators';