[Bug]: Inconsistently parsing between TypeScript and Babel for decorator auto accessors

[sosukesuzuki]

💻

• Would you like to work on a fix?

How are you using Babel?

Other (Next.js, Gatsby, vue-cli, ...)

Input code

class C {
  accessor
  property
}

Configuration file name

No response

Configuration

Use @babel/parser as a Node.js API.

Current and expected behavior

current:

@babel/parser with typescript plugin parses the input code to:

// pseudo AST
{
  type: class
  children: [
    property ( name = "accessor" ),
    property ( name = "foo" )
  ]
}

But TypeScript Compiler parses the input code to:

// pseudo AST
{
  type: class
  children: [
    accessor property ( name = "foo" )
  ]
}

expected:

Must match the decorator spec. I don't know which is correct.
If TypeScript Compiler behavior is wrong, we should report to microsoft/typescript repository.

Environment

Environment does not matter.

Possible solution

Fix parsing logic

Additional context

I noticed this while working on printing accessor property syntax for Prettier ( prettier/prettier#13919 )

[liuxingbaoyu]

This code is also legal in js and is parsed into two properties.
In addition, even if I set the language to JavaScript in the ts repl, it still produces output like ts.
So I'm guessing it's a ts bug.

[liuxingbaoyu]

https://www.typescriptlang.org/play?noImplicitAny=false&ts=4.9.3&filetype=js#code/MYGwhgzhAEDC0G8CwAoa0zGAUygewCdV0AHAvE7AgFwE9UBfIA

[JLHwung]

This is a TS bug. The spec draft:

FieldDefinition[Yield, Await] :
  accessor [no LineTerminator here] ClassElementName[?Yield, ?Await] Initializer[+In, ?Yield, ?Await]opt

disables line terminator after accessor in the accessor property.

[sosukesuzuki]

Thanks, I reported to TS repo microsoft/TypeScript#51707