fix(webpack): use webpack-merge v4 to support merge.smart and node 10

lib/build.spec.js

@@ -65,5 +65,29 @@ describe('build', () => {
         }),
       ).rejects.toThrow('Cannot find module');
     });
+
+    it('should merge webpack custom config', async () => {
+      const script = `module.exports = () => console.log("hello world")`;
+      setupFunction(script, 'index.js');
+
+      const webpackConfig = `module.exports = { resolve: { extensions: ['.custom'] } }`;
+      const customWebpackConfigDir = path.join(buildTemp, 'webpack');
+      const userWebpackConfig = path.join(customWebpackConfigDir, 'webpack.js');
+      fs.mkdirSync(customWebpackConfigDir, { recursive: true });
+      fs.writeFileSync(userWebpackConfig, webpackConfig);
+
+      const stats = await build.run(functions, {
+        userWebpackConfig,
+      });
+      expect(stats.compilation.errors).toHaveLength(0);
+      expect(stats.compilation.options.resolve.extensions).toEqual([
+        '.wasm',
+        '.mjs',
+        '.js',
+        '.json',
+        '.ts',
+        '.custom',
+      ]);
+    });
   });
 });

package.json

@@ -44,7 +44,7 @@
     "jwt-decode": "^2.2.0",
     "toml": "^3.0.0",
     "webpack": "^4.43.0",
-    "webpack-merge": "^5.0.9"
+    "webpack-merge": "^4.2.2"
   },
   "devDependencies": {
     "@commitlint/cli": "^9.0.0",