From bb1483707f3af9bedae115fb51c6084888f0e950 Mon Sep 17 00:00:00 2001
From: Nitin Kumar <snitin315@gmail.com>
Date: Sun, 18 Apr 2021 07:31:00 +0530
Subject: [PATCH] fix: improve parsing of `--env` flag

---
 packages/webpack-cli/lib/webpack-cli.js               | 11 +++++++++--
 .../type/function-with-env/function-with-env.test.js  | 10 ++++++++++
 .../config/type/function-with-env/webpack.config.js   |  8 ++++++++
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/packages/webpack-cli/lib/webpack-cli.js b/packages/webpack-cli/lib/webpack-cli.js
index c5ba9ff9e15..b8b0db06b69 100644
--- a/packages/webpack-cli/lib/webpack-cli.js
+++ b/packages/webpack-cli/lib/webpack-cli.js
@@ -373,8 +373,11 @@ class WebpackCLI {
             {
                 name: 'env',
                 type: (value, previous = {}) => {
+                    // for https://github.com/webpack/webpack-cli/issues/2642
+                    const regExpForSplitting = (value.match(/=/g) || []).length === 1 ? /=/ : /=(.+)/;
+
                     // This ensures we're only splitting by the first `=`
-                    const [allKeys, val] = value.split(/=(.+)/, 2);
+                    const [allKeys, val] = value.split(regExpForSplitting, 2);
                     const splitKeys = allKeys.split(/\.(?!$)/);
 
                     let prevRef = previous;
@@ -389,7 +392,11 @@ class WebpackCLI {
                         }
 
                         if (index === splitKeys.length - 1) {
-                            prevRef[someKey] = val || true;
+                            if (typeof val === 'string') {
+                                prevRef[someKey] = val;
+                            } else {
+                                prevRef[someKey] = true;
+                            }
                         }
 
                         prevRef = prevRef[someKey];
diff --git a/test/build/config/type/function-with-env/function-with-env.test.js b/test/build/config/type/function-with-env/function-with-env.test.js
index b31b2e546ad..2c07fb01697 100644
--- a/test/build/config/type/function-with-env/function-with-env.test.js
+++ b/test/build/config/type/function-with-env/function-with-env.test.js
@@ -117,6 +117,16 @@ describe('function configuration', () => {
         expect(existsSync(resolve(__dirname, './dist/true.js'))).toBeTruthy();
     });
 
+    it('Supports empty string', async () => {
+        const { exitCode, stderr, stdout } = await run(__dirname, ['--env', `foo=''`]);
+
+        expect(exitCode).toBe(0);
+        expect(stderr).toBeFalsy();
+        expect(stdout).toBeTruthy();
+        // Should generate the appropriate files
+        expect(existsSync(resolve(__dirname, './dist/empty-string.js'))).toBeTruthy();
+    });
+
     it('is able to understand multiple env flags', async () => {
         const { exitCode, stderr, stdout } = await run(__dirname, ['--env', 'isDev', '--env', 'verboseStats', '--env', 'envMessage']);
 
diff --git a/test/build/config/type/function-with-env/webpack.config.js b/test/build/config/type/function-with-env/webpack.config.js
index 35efedbbb0d..8fe8deb18e8 100644
--- a/test/build/config/type/function-with-env/webpack.config.js
+++ b/test/build/config/type/function-with-env/webpack.config.js
@@ -9,6 +9,14 @@ module.exports = (env) => {
             },
         };
     }
+    if (env.foo === `''`) {
+        return {
+            entry: './a.js',
+            output: {
+                filename: 'empty-string.js',
+            },
+        };
+    }
     return {
         entry: './a.js',
         mode: 'development',