TypeScript incorrectly handles naughty strings in json

[Gabriel-Alves-Cunha]

Bug Report

🔎 Search Terms

bad naughty json string

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about bad strings in json

⏯ Playground Link

Playground link with relevant code

When you enter the playground, an alert message will appear:

Click at 'Cancel', otherwise, you'll not see the errors at the errors tab.

💻 Code

Code here will tell you nothing, you should see the playground above. Don't worry, it's not complicated at all.

🙁 Actual behavior

There are several errors reported by the compiler, you can see them in the image below:

🙂 Expected behavior

I believe the compiler should be able to correctly handle these potencial problematic strings.

[fatcerberus]

I mean it seems to me like the purpose of the warning is precisely because the compiler won’t be able to handle the file correctly otherwise…

[ferrybig]

Typescript expects JavaScript or TypeScript code, you are providing it json which is not a valid JavaScript or TypeScript input, as JSON allows raw characters that are not allowed in JavaScript and TypeScript.

If you do not want to encode your JSOn input into a valid JavaScript/TypeScript input, place it in a seperate .json file and import it

[Josh-Cena]

JSON allows raw characters that are not allowed in JavaScript and TypeScript.

Not the case anymore after https://github.com/tc39/proposal-json-superset—all JSON are now valid ES expressions, including unescaped LS and PS in string literals.

[RyanCavanaugh]

Can we use more technically-precise terminology than "bad" or "naughty" ? What is the nature of the strings that aren't handled correctly?

[Josh-Cena]

@RyanCavanaugh The buggy code reported here has exactly one problem:

const myjson = [
  "
test
",
] as const;

This string has a U+2029 Paragraph Separator character on both ends. After JSON-superset, this should be valid ES code, but seems the TS lexer is not updated yet. I assume the same error would occur with U+2028 Line Separator.