Support ChainExpression type for optional chaining

[mjhenkes]

Feature request or bug?

babelParser@7.11.0 changed how optional chaining gets represented in an AST. Previously the optional chain was represented as an OptionalMemberExpression, now the optional chain is broken into two nodes a ChainExpression and a MemberExpression.

I asked babel if this was a breaking change and they clarified that this is an intentional change. See Babel issue #11908

I stumbled upon this while trying to use react-doc-gen against a component with optional chanining and the ast-types library that it uses fails when it tries to understand the 'ChainExpression' type. See react-doc-gen issue #463

I'm currently working around this issue by locking in the projects babel dependencies in the package.json

For example:

  "devDependencies": {
-    "@babel/core": "^7.5.0",
+    "@babel/core": "7.10.5",
+    "@babel/parser": "7.10.5",

However this isn't a good long term fix. I would be ideal if ast-types was updated to support the chainExpression type.

[jquense]

🙏 anything i can do to help with this?

[ethancrook99]

I made a PR for a possible fix here.

[mjhenkes]

Thank you @ethancrook99 and @benjamn ❤️