[Bug]: TSLiteralType should accept UnaryExpression

[alexandre-bbx]

💻

• Would you like to work on a fix?

How are you using Babel?

Programmatic API (babel.transform, babel.parse)

Input code

See REPL: https://runkit.com/alexandre-cai/60a2ae9feaab4400130133c8

transform(`
  type Test = 1 | -1;
`, {
  parserOpts: {
    plugins: ["typescript"],
  },
  plugins: [
    ({ types: t }) => ({
      visitor: {
        TSLiteralType(path) {
          path.node = t.tsLiteralType(path.node.literal)
        }
      }
    }),
  ],
})

Configuration file name

No response

Configuration

No response

Current and expected behavior

Babel currently accepts UnaryExpression while parsing TSLiteralType, but can’t generate one. Output:

TypeError: unknown: Property literal of TSLiteralType expected node to be of a type 
["NumericLiteral","StringLiteral","BooleanLiteral","BigIntLiteral"] but instead got "UnaryExpression"

Environment

• @babel/core: 7.14.2

Possible solution

https://github.com/babel/babel/blob/main/packages/babel-types/src/definitions/typescript.ts#L342
Add UnaryExpression.

Additional context

No response

[babel-bot]

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[nicolo-ribaudo]

Thanks for the bug report!
The accepted type should be:

• one of "NumericLiteral","StringLiteral","BooleanLiteral","BigIntLiteral"
• or a UnaryExpression whose argument is one of "NumericLiteral","StringLiteral","BooleanLiteral","BigIntLiteral".

It can be implemented by replacing https://github.com/babel/babel/blob/main/packages/babel-types/src/definitions/typescript.ts#L342 with a custom validator, similarly to

babel/packages/babel-types/src/definitions/core.ts

Line 659 in 9d620c2

validate: (function () {

.

[alexandre-bbx]

I think UnaryExpression should only accept NumericLiteral and BigIntLiteral with an operand of -.

[Patil2099]

@nicolo-ribaudo I would love to help in fixing this issue. I am new to this project. Can you guide me a little more on closing this issue? Thanks!

[nicolo-ribaudo]

@Patil2099 You follow these steps: (you need to have make and yarn available on your machine)

1. Fork the repo
2. Run git clone https://github.com/<YOUR_USERNAME>/babel.git && cd babel
3. Run yarn && make bootstrap
4. Wait ⏳
5. Run make watch (or make build whenever you change a file)
6. Add one or more tests in https://github.com/babel/babel/tree/main/packages/babel-types/test/builders/typescript
7. Update the code!
8. yarn jest babel-types to run the tests
9. If it is working, run make test to run all the tests
10. Run git push and open a PR!

I'm assigning this issue to you; if you need more help feel free to ask!

[tony-go]

Hi 👋

Is this issue always available ?

Cc @nicolo-ribaudo @Patil2099

[nicolo-ribaudo]

@tony-go Let's give @Patil2099 a few more days to work on this. If @Patil2099 doesn't reply within Wednesday, you can work on this.

As an alternative, if you prefer I opened #13399.

[tony-go]

Hey @nicolo-ribaudo

Yeah for sure ! ✌🏼

[nicolo-ribaudo]

@Patil2099 Hi! Are you still working on this?

[lala7573]

Is this issue available? I'd like to try this one.