javascript - Upgrade to Babel 7: Cannot read property 'bindings' of null

Question

I just upgraded to Babel 7 (from 6) by running these commands:

npm remove babel-cli
npm install --save-dev @babel/cli @babel/core @babel/preset-env

Here is my .babelrc file:

{ "presets": ["env"] }

Then I ran:

babel js/src --out-dir js/dist

And it results in:

TypeError: Cannot read property 'bindings' of null
    at Scope.moveBindingTo (/xyz/node_modules/@babel/traverse/lib/scope/index.js:867:13)
    at BlockScoping.updateScopeInfo (/xyz/node_modules/babel-plugin-transform-es2015-block-scoping/lib/index.js:364:17)
    at BlockScoping.run (/xyz/node_modules/babel-plugin-transform-es2015-block-scoping/lib/index.js:330:12)
    at PluginPass.BlockStatementSwitchStatementProgram (/xyz/node_modules/babel-plugin-transform-es2015-block-scoping/lib/index.js:70:24)
    at newFn (/xyz/node_modules/@babel/traverse/lib/visitors.js:193:21)
    at NodePath._call (/xyz/node_modules/@babel/traverse/lib/path/context.js:53:20)
    at NodePath.call (/xyz/node_modules/@babel/traverse/lib/path/context.js:40:17)
    at NodePath.visit (/xyz/node_modules/@babel/traverse/lib/path/context.js:88:12)
    at TraversalContext.visitQueue (/xyz/node_modules/@babel/traverse/lib/context.js:118:16)
    at TraversalContext.visitSingle (/xyz/node_modules/@babel/traverse/lib/context.js:90:19)

What did I do wrong?

Answer 1

In your .babelrc file, change

{ "presets": ["env"] } 

to

{ "presets": ["@babel/preset-env"] }

(and install that package if you haven't already).

In your .babelrc you are still referencing the package babel-preset-env (which is for 6.x), you want to reference @babel/preset-env instead (which is for 7.x).

https://github.com/babel/babel/issues/6186#issuecomment-366556833

Note: you should also make this change in webpack.config.js if it is there as well.

Here is the sample webpack config section where you should change the preset:

use: {
  loader: 'babel-loader',
  options: {
    // Here you should change 'env' to '@babel/preset-env'
    presets: ['@babel/preset-env'],
  },
},