feat: show possible values for option in help output

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

@@ -1363,10 +1363,31 @@ class WebpackCLI {
                     );
                 }
 
+                const flag = this.getBuiltInOptions().find(
+                    (flag) => option.long === `--${flag.name}`,
+                );
+
+                if (flag && flag.configs) {
+                    const possibleValues = flag.configs.reduce((accumulator, currentValue) => {
+                        if (currentValue.values) {
+                            return accumulator.concat(currentValue.values);
+                        } else {
+                            return accumulator;
+                        }
+                    }, []);
+
+                    if (possibleValues.length > 0) {
+                        this.logger.raw(
+                            `${bold("Possible values:")} ${JSON.stringify(
+                                possibleValues.join(" | "),
+                            )}`,
+                        );
+                    }
+                }
+
                 this.logger.raw("");
 
                 // TODO implement this after refactor cli arguments
-                // logger.raw('Possible values: foo | bar');
                 // logger.raw('Documentation: https://webpack.js.org/option/name/');
             } else {
                 outputIncorrectUsageOfHelp();

test/help/__snapshots__/help.test.js.snap.devServer3.webpack5

@@ -2540,6 +2540,20 @@ CLI documentation: https://webpack.js.org/api/cli/.
 Made with ♥ by the webpack team."
 `;
 
+exports[`help should show help information using the "help --cache-type" option: stderr 1`] = `""`;
+
+exports[`help should show help information using the "help --cache-type" option: stdout 1`] = `
+"Usage: webpack --cache-type <value>
+Description: In memory caching. Filesystem caching.
+Possible values: \\"memory | filesystem\\"
+
+To see list of all supported commands and options run 'webpack --help=verbose'.
+
+Webpack documentation: https://webpack.js.org/.
+CLI documentation: https://webpack.js.org/api/cli/.
+Made with ♥ by the webpack team."
+`;
+
 exports[`help should show help information using the "help --color" option: stderr 1`] = `""`;
 
 exports[`help should show help information using the "help --color" option: stdout 1`] = `
@@ -2560,6 +2574,7 @@ exports[`help should show help information using the "help --mode" option: stder
 exports[`help should show help information using the "help --mode" option: stdout 1`] = `
 "Usage: webpack --mode <value>
 Description: Defines the mode to pass to webpack.
+Possible values: \\"development | production | none\\"
 
 To see list of all supported commands and options run 'webpack --help=verbose'.
 
@@ -2571,6 +2586,7 @@ Made with ♥ by the webpack team."
 exports[`help should show help information using the "help --mode" option: stdout 2`] = `
 "Usage: webpack --mode <value>
 Description: Defines the mode to pass to webpack.
+Possible values: \\"development | production | none\\"
 
 To see list of all supported commands and options run 'webpack --help=verbose'.
 
@@ -2610,6 +2626,7 @@ exports[`help should show help information using the "help --stats" option: stde
 exports[`help should show help information using the "help --stats" option: stdout 1`] = `
 "Usage: webpack --stats [value]
 Description: It instructs webpack on how to treat the stats e.g. verbose.
+Possible values: \\"none | summary | errors-only | errors-warnings | minimal | normal | detailed | verbose\\"
 
 To see list of all supported commands and options run 'webpack --help=verbose'.
 
@@ -2624,6 +2641,7 @@ exports[`help should show help information using the "help --target" option: std
 "Usage: webpack --target <value...>
 Short: webpack -t <value...>
 Description: Sets the build target e.g. node.
+Possible values: \\"false\\"
 
 To see list of all supported commands and options run 'webpack --help=verbose'.
 
@@ -2678,6 +2696,7 @@ exports[`help should show help information using the "help serve --mode" option:
 exports[`help should show help information using the "help serve --mode" option: stdout 1`] = `
 "Usage: webpack serve --mode <value>
 Description: Defines the mode to pass to webpack.
+Possible values: \\"development | production | none\\"
 
 To see list of all supported commands and options run 'webpack --help=verbose'.
 

test/help/__snapshots__/help.test.js.snap.devServer4.webpack5

@@ -2670,6 +2670,20 @@ CLI documentation: https://webpack.js.org/api/cli/.
 Made with ♥ by the webpack team."
 `;
 
+exports[`help should show help information using the "help --cache-type" option: stderr 1`] = `""`;
+
+exports[`help should show help information using the "help --cache-type" option: stdout 1`] = `
+"Usage: webpack --cache-type <value>
+Description: In memory caching. Filesystem caching.
+Possible values: \\"memory | filesystem\\"
+
+To see list of all supported commands and options run 'webpack --help=verbose'.
+
+Webpack documentation: https://webpack.js.org/.
+CLI documentation: https://webpack.js.org/api/cli/.
+Made with ♥ by the webpack team."
+`;
+
 exports[`help should show help information using the "help --color" option: stderr 1`] = `""`;
 
 exports[`help should show help information using the "help --color" option: stdout 1`] = `
@@ -2690,6 +2704,7 @@ exports[`help should show help information using the "help --mode" option: stder
 exports[`help should show help information using the "help --mode" option: stdout 1`] = `
 "Usage: webpack --mode <value>
 Description: Defines the mode to pass to webpack.
+Possible values: \\"development | production | none\\"
 
 To see list of all supported commands and options run 'webpack --help=verbose'.
 
@@ -2701,6 +2716,7 @@ Made with ♥ by the webpack team."
 exports[`help should show help information using the "help --mode" option: stdout 2`] = `
 "Usage: webpack --mode <value>
 Description: Defines the mode to pass to webpack.
+Possible values: \\"development | production | none\\"
 
 To see list of all supported commands and options run 'webpack --help=verbose'.
 
@@ -2740,6 +2756,7 @@ exports[`help should show help information using the "help --stats" option: stde
 exports[`help should show help information using the "help --stats" option: stdout 1`] = `
 "Usage: webpack --stats [value]
 Description: It instructs webpack on how to treat the stats e.g. verbose.
+Possible values: \\"none | summary | errors-only | errors-warnings | minimal | normal | detailed | verbose\\"
 
 To see list of all supported commands and options run 'webpack --help=verbose'.
 
@@ -2754,6 +2771,7 @@ exports[`help should show help information using the "help --target" option: std
 "Usage: webpack --target <value...>
 Short: webpack -t <value...>
 Description: Sets the build target e.g. node.
+Possible values: \\"false\\"
 
 To see list of all supported commands and options run 'webpack --help=verbose'.
 
@@ -2808,6 +2826,7 @@ exports[`help should show help information using the "help serve --mode" option:
 exports[`help should show help information using the "help serve --mode" option: stdout 1`] = `
 "Usage: webpack serve --mode <value>
 Description: Defines the mode to pass to webpack.
+Possible values: \\"development | production | none\\"
 
 To see list of all supported commands and options run 'webpack --help=verbose'.
 

test/help/help.test.js

@@ -1,6 +1,6 @@
 "use strict";
 
-const { run, normalizeStderr, normalizeStdout } = require("../utils/test-utils");
+const { run, normalizeStderr, normalizeStdout, isWebpack5 } = require("../utils/test-utils");
 
 describe("help", () => {
     it('should show help information using the "--help" option', async () => {
@@ -242,6 +242,18 @@ describe("help", () => {
         expect(normalizeStdout(stdout)).toMatchSnapshot("stdout");
     });
 
+    it('should show help information using the "help --cache-type" option', async () => {
+        const { exitCode, stderr, stdout } = await run(__dirname, ["help", "--cache-type"]);
+
+        if (isWebpack5) {
+            expect(exitCode).toBe(0);
+            expect(normalizeStderr(stderr)).toMatchSnapshot("stderr");
+            expect(normalizeStdout(stdout)).toMatchSnapshot("stdout");
+        } else {
+            expect(exitCode).toBe(2);
+        }
+    });
+
     it('should show help information using the "help --no-stats" option', async () => {
         const { exitCode, stderr, stdout } = await run(__dirname, ["help", "--no-stats"]);