From 491a582620b64ed4acbccd04f687adc28a5e4cff Mon Sep 17 00:00:00 2001
From: James George <jamesgeorge998001@gmail.com>
Date: Mon, 2 Nov 2020 18:41:01 +0530
Subject: [PATCH] feat: suggest the closest match based on the Levenshtein
 distance algorithm (#2010)

* feat: suggest the closest match for an unknown flag

* tests: add test case for flag suggestion

* tests: assert for exit code
---
 packages/webpack-cli/lib/bootstrap.js | 6 ++++++
 packages/webpack-cli/package.json     | 1 +
 test/unknown/unknown.test.js          | 9 ++++++++-
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/packages/webpack-cli/lib/bootstrap.js b/packages/webpack-cli/lib/bootstrap.js
index 56996ec64c7..b6fc82879c6 100644
--- a/packages/webpack-cli/lib/bootstrap.js
+++ b/packages/webpack-cli/lib/bootstrap.js
@@ -3,6 +3,7 @@ const { core } = require('./utils/cli-flags');
 const logger = require('./utils/logger');
 const { isCommandUsed } = require('./utils/arg-utils');
 const argParser = require('./utils/arg-parser');
+const leven = require('leven');
 
 process.title = 'webpack-cli';
 
@@ -39,6 +40,11 @@ const runCLI = async (cliArgs) => {
         if (parsedArgs.unknownArgs.length > 0) {
             parsedArgs.unknownArgs.forEach(async (unknown) => {
                 logger.error(`Unknown argument: ${unknown}`);
+                const strippedFlag = unknown.substr(2);
+                const { name: suggestion } = core.find((flag) => leven(strippedFlag, flag.name) < 3);
+                if (suggestion) {
+                    logger.raw(`Did you mean --${suggestion}?`);
+                }
             });
 
             process.exit(2);
diff --git a/packages/webpack-cli/package.json b/packages/webpack-cli/package.json
index c6e0534cd41..67855ac6601 100644
--- a/packages/webpack-cli/package.json
+++ b/packages/webpack-cli/package.json
@@ -37,6 +37,7 @@
     "execa": "^4.1.0",
     "import-local": "^3.0.2",
     "interpret": "^2.2.0",
+    "leven": "^3.1.0",
     "rechoir": "^0.7.0",
     "v8-compile-cache": "^2.2.0",
     "webpack-merge": "^4.2.2"
diff --git a/test/unknown/unknown.test.js b/test/unknown/unknown.test.js
index 8352b345d6f..903122b2495 100644
--- a/test/unknown/unknown.test.js
+++ b/test/unknown/unknown.test.js
@@ -2,8 +2,15 @@ const { run } = require('../utils/test-utils');
 
 describe('unknown behaviour', () => {
     it('warns the user if an unknown flag is passed in', () => {
-        const { stderr } = run(__dirname, ['--unknown']);
+        const { stderr, exitCode } = run(__dirname, ['--unknown']);
         expect(stderr).toBeTruthy();
         expect(stderr).toContain('Unknown argument: --unknown');
+        expect(exitCode).toBe(2);
+    });
+    it('suggests the closest match to an unknown flag', () => {
+        const { stderr, stdout, exitCode } = run(__dirname, ['--entyr', './a.js']);
+        expect(stderr).toContain('Unknown argument: --entyr');
+        expect(stdout).toContain('Did you mean --entry?');
+        expect(exitCode).toBe(2);
     });
 });