Feature request: new value for the preserveParens option

Would be good to have a mode in which ParenthesizedExpression nodes would be created only for parentheses used for JSDoc type assertions.

The syntax of JSDoc type assertions is simple: @type {...} JSDoc comment followed by a parenthesized expression. Anything else is not a type assertion. Reference: Closure Compiler, TypeScript.

[thorn0]

I am not sure if recursive type casting is possible

Yes, possible. Also they can be nested directly (people really use this):

/** @type MyType */ (/** @type any */ (x))

What’s the use case for this? And why do you want to turn off ParenthesizedExpression ? It’s in the spec

If you mean ESTree, ParenthesizedExpression is not there. It’s a non-standard extension. Overall, ESTree’s approach is to ignore insignificant parentheses. However, the JSDoc convention that uses such parentheses is widespread and important. So from the point of view of tools like formatters and linters, it makes sense to create these non-standard nodes only for JSDoc. In other cases, they only get in the way. E.g. Prettier doesn’t simply print the AST. It also does a lot of checks of the AST structure along the way to choose between different ways to print things. Taking ParenthesizedExpression nodes into account in all those checks would ridiculously complicate them, so actually what happens now in Prettier is an extra step that removes all ParenthesizedExpressions that aren’t JSDoc type assertions from the AST before passing it to printing.

Name it thorn

I sincerely believe something like PreserveJsdocParens would be a slightly better name. 😆

[3cp]

I see.