add opts.ecmaVersion

Author: substack

index.js

@@ -82,7 +82,7 @@ function createStream (opts) {
     let ast
     const string = transformAst(source, {
       locations: true,
-      ecmaVersion: 10,
+      ecmaVersion: opts.ecmaVersion !== undefined ? opts.ecmaVersion : 10,
       inputFilename: row.file
     }, (node) => {
       if (node.type === 'Program') ast = node

readme.md

@@ -95,6 +95,10 @@ Handler called when a module cannot be tree-shaked for some reason.
 Handler called when tree-shaking is skipped entirely, usually because there is a dynamic `require` call in the source.
 `reasons` is an array of reasons for skipping tree-shaking.
 
+### `ecmaVersion`
+
+Parse with this ecmaVersion as interpreted by acorn. (default: 10)
+
 ## License
 
 [MIT](./LICENSE)