From cf032f0178ffdb014cce62d350ab1b27fc4f764d Mon Sep 17 00:00:00 2001
From: merceyz <merceyz@users.noreply.github.com>
Date: Tue, 13 Apr 2021 12:00:11 +0200
Subject: [PATCH] fix(core-server): resolve builder relative to config

---
 lib/core-server/src/utils/get-preview-builder.ts | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/lib/core-server/src/utils/get-preview-builder.ts b/lib/core-server/src/utils/get-preview-builder.ts
index 111a5694741c..506ba16edc3d 100644
--- a/lib/core-server/src/utils/get-preview-builder.ts
+++ b/lib/core-server/src/utils/get-preview-builder.ts
@@ -1,16 +1,17 @@
 import path from 'path';
 import { getInterpretedFile, serverRequire, Options } from '@storybook/core-common';
 
-const DEFAULT_WEBPACK = 'webpack4';
-
 export async function getPreviewBuilder(configDir: Options['configDir']) {
   const main = path.resolve(configDir, 'main');
   const mainFile = getInterpretedFile(main);
   const { core } = mainFile ? serverRequire(mainFile) : { core: null };
-  const builder = core?.builder || DEFAULT_WEBPACK;
-  const builderPackage = ['webpack4', 'webpack5'].includes(builder)
-    ? `@storybook/builder-${builder}`
-    : builder;
+  const builder = core?.builder;
+  const builderPackage = builder
+    ? require.resolve(
+        ['webpack4', 'webpack5'].includes(builder) ? `@storybook/builder-${builder}` : builder,
+        { paths: [main] }
+      )
+    : require.resolve('@storybook/builder-webpack4');
 
   const previewBuilder = await import(builderPackage);
   return previewBuilder;