feat: allow string value for '--hot' (#2444)

Author: snitin315

OPTIONS.md

@@ -10,7 +10,7 @@ Options:
   -m, --merge                                                                        Merge two or more configurations using 'webpack-merge'.
   --env <value...>                                                                   Environment passed to the configuration when it is a function.
   --node-env <value>                                                                 Sets process.env.NODE_ENV to the specified value.
-  -h, --hot                                                                          Enables Hot Module Replacement
+  -h, --hot [value]                                                                  Enables Hot Module Replacement
   --no-hot                                                                           Disables Hot Module Replacement.
   --analyze                                                                          It invokes webpack-bundle-analyzer plugin to get bundle information.
   --progress [value]                                                                 Print compilation progress during build.

packages/webpack-cli/README.md

@@ -91,7 +91,7 @@ npx webpack-cli --help verbose
   -d, --devtool <value>         Determine source maps to use.
   --no-devtool                  Do not generate source maps.
   --entry <value...>            The entry point(s) of your application e.g. ./src/main.js.
-  -h, --hot                     Enables Hot Module Replacement
+  -h, --hot [value]             Enables Hot Module Replacement
   --no-hot                      Disables Hot Module Replacement
   --mode <value>                Defines the mode to pass to webpack.
   --name <value>                Name of the configuration. Used when loading multiple configurations.

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

@@ -382,7 +382,7 @@ class WebpackCLI {
             {
                 name: 'hot',
                 alias: 'h',
-                type: Boolean,
+                type: [Boolean, String],
                 negative: true,
                 description: 'Enables Hot Module Replacement',
                 negatedDescription: 'Disables Hot Module Replacement.',
@@ -1456,6 +1456,11 @@ class WebpackCLI {
             process.exit(2);
         }
 
+        if (typeof options.hot === 'string' && options.hot !== 'only') {
+            this.logger.error(`'${options.hot}' is an invalid value for the --hot option. Use 'only' instead.`);
+            process.exit(2);
+        }
+
         const outputHints = (configOptions) => {
             if (
                 configOptions.watch &&

test/hot/hot-flag.test.js

@@ -13,6 +13,23 @@ describe('--hot flag', () => {
         expect(readFileSync(resolve(__dirname, './dist/main.js')).toString()).toContain('webpackHotUpdate');
     });
 
+    it('should be successful when --hot=only is passed', () => {
+        const { exitCode, stderr, stdout } = run(__dirname, ['--hot', 'only']);
+
+        expect(exitCode).toBe(0);
+        expect(stderr).toBeFalsy();
+        expect(stdout).toBeTruthy();
+        expect(readFileSync(resolve(__dirname, './dist/main.js')).toString()).toContain('webpackHotUpdate');
+    });
+
+    it('should throw an error for invalid value', () => {
+        const { exitCode, stderr, stdout } = run(__dirname, ['--hot', 'unknown']);
+
+        expect(exitCode).toBe(2);
+        expect(stderr).toContain(`[webpack-cli] 'unknown' is an invalid value for the --hot option. Use 'only' instead.`);
+        expect(stdout).toBeFalsy();
+    });
+
     it('should be successful when --no-hot is passed', () => {
         const { exitCode, stderr, stdout } = run(__dirname, ['--no-hot']);