fix: allow Flow syntax in stories

code/lib/csf-tools/src/babelParse.ts

@@ -1,24 +1,41 @@
-import * as parser from '@babel/parser';
+import * as babelParser from '@babel/parser';
 import * as recast from 'recast';
 import type { ParserOptions } from '@babel/parser';
 
+function parseWithFlowOrTypescript(source: string, parserOptions: babelParser.ParserOptions) {
+  const flowCommentPattern = /^\s*\/\/\s*@flow/;
+  const useFlowPlugin = flowCommentPattern.test(source);
+
+  const parserPlugins: babelParser.ParserOptions['plugins'] = useFlowPlugin
+    ? ['flow']
+    : ['typescript'];
+
+  // Merge the provided parserOptions with the custom parser plugins
+  const mergedParserOptions = {
+    ...parserOptions,
+    plugins: [...parserOptions.plugins, ...parserPlugins],
+  };
+
+  return babelParser.parse(source, mergedParserOptions);
+}
+
 export const parserOptions: ParserOptions = {
   sourceType: 'module',
   // FIXME: we should get this from the project config somehow?
-  plugins: ['jsx', 'typescript', 'decorators-legacy', 'classProperties'],
+  plugins: ['jsx', 'decorators-legacy', 'classProperties'],
   tokens: true,
 };
 
 export const babelParse = (code: string) => {
   return recast.parse(code, {
     parser: {
       parse(source: string) {
-        return parser.parse(source, parserOptions);
+        return parseWithFlowOrTypescript(source, parserOptions);
       },
     },
   });
 };
 
 export const babelParseExpression = (code: string) => {
-  return parser.parseExpression(code, parserOptions);
+  return babelParser.parseExpression(code, parserOptions);
 };