Add a warning if webpack was also added as a dependency by the user

Author: Lyrkan

index.js

@@ -17,6 +17,8 @@ const logger = require('./lib/logger');
 const parseRuntime = require('./lib/config/parse-runtime');
 const chalk = require('chalk');
 const levenshtein = require('fast-levenshtein');
+const fs = require('fs');
+const path = require('path');
 
 let webpackConfig = null;
 let runtimeConfig = require('./lib/context').runtimeConfig;
@@ -26,6 +28,26 @@ function initializeWebpackConfig() {
         logger.verbose();
     }
 
+    // Display a warning if webpack is listed as a [dev-]dependency
+    try {
+        const packageInfo = JSON.parse(
+            fs.readFileSync(path.resolve(runtimeConfig.context, 'package.json'))
+        );
+
+        if (packageInfo) {
+            const dependencies = new Set([
+                ...(packageInfo.dependencies ? Object.keys(packageInfo.dependencies) : []),
+                ...(packageInfo.devDependencies ? Object.keys(packageInfo.devDependencies) : []),
+            ]);
+
+            if (dependencies.has('webpack')) {
+                logger.warning('Webpack is already provided by Webpack Encore, also adding it to your package.json file may cause issues.');
+            }
+        }
+    } catch (e) {
+        logger.warning('Could not read package.json file.');
+    }
+
     webpackConfig = new WebpackConfig(runtimeConfig);
 }
 

test/bin/encore.js

@@ -25,6 +25,15 @@ describe('bin/encore.js', function() {
         testSetup.emptyTmpDir();
         const testDir = testSetup.createTestAppDir();
 
+        fs.writeFileSync(
+            path.join(testDir, 'package.json'),
+            `{
+                "devDependencies": {
+                    "@symfony/webpack-encore": "*"
+                }
+            }`
+        );
+
         fs.writeFileSync(
             path.join(testDir, 'webpack.config.js'),
             `
@@ -45,6 +54,8 @@ module.exports = Encore.getWebpackConfig();
                 throw new Error(`Error executing encore: ${err} ${stderr} ${stdout}`);
             }
 
+            expect(stdout).to.not.contain('Webpack is already provided by Webpack Encore');
+
             done();
         });
     });
@@ -142,4 +153,44 @@ module.exports = Encore.getWebpackConfig();
             done();
         });
     });
+
+    it('Display a warning message when webpack is also added to the package.json file', (done) => {
+        testSetup.emptyTmpDir();
+        const testDir = testSetup.createTestAppDir();
+
+        fs.writeFileSync(
+            path.join(testDir, 'package.json'),
+            `{
+                "devDependencies": {
+                    "@symfony/webpack-encore": "*",
+                    "webpack": "*"
+                }
+            }`
+        );
+
+        fs.writeFileSync(
+            path.join(testDir, 'webpack.config.js'),
+            `
+const Encore = require('../../index.js');
+Encore
+    .setOutputPath('build/')
+    .setPublicPath('/build')
+    .addEntry('main', './js/no_require')
+;
+
+module.exports = Encore.getWebpackConfig();
+            `
+        );
+
+        const binPath = path.resolve(__dirname, '../', '../', 'bin', 'encore.js');
+        exec(`node ${binPath} dev --context=${testDir}`, { cwd: testDir }, (err, stdout, stderr) => {
+            if (err) {
+                throw new Error(`Error executing encore: ${err} ${stderr} ${stdout}`);
+            }
+
+            expect(stdout).to.contain('Webpack is already provided by Webpack Encore');
+
+            done();
+        });
+    });
 });