types/node: make util.inspect.custom a 'unique symbol', not only a 'symbol'?

[emmanueltouzery]

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In node, if we want custom rendering for custom objects in the REPL and in console.log, we used to have to override inspect(). In recent versions of node, we must instead override [util.inspect.custom], which is a symbol. See the documentation: https://nodejs.org/api/util.html#util_util_inspect_custom [update: better link]

The implementation of custom was changed recently as well: https://github.com/nodejs/node/commit/dadd6e16888baac8fd110432b81f3fd1237be3e1#diff-a43208147d795be6dd3517c53226e37dL402

I think that in the type definitions, the type of custom should not be symbol as it is now, but unique symbol. The reason being that we can't define class members with [util.inspect.custom] as it is, as the compiler says:

error TS1169: A computed property name in an interface must refer to an expression whose type is a literal type or a 'unique symbol' type.

My current workaround is to say...

import * as util from 'util';

// @ts-ignore
export const inspect: unique symbol = util.inspect.custom;

and later [inspect](): string. Even casting to any is not enough, I need @ts-ignore.

PS: I tried to make a PR and failed. It was https://github.com/DefinitelyTyped/DefinitelyTyped/pull/30237

[SimonSchick]

Not going to work given the fact that the node typings have to support a very old version of TS.

[emmanueltouzery]

it's really not rare that I wish that there was some #ifdef mechanism in typescript, with version constraints :-(

It's quite painful as it is now. One would wish to define the constant oneself, ignoring the one exported by node, but as you can see in the commit I pasted, they've been changing it through time.. Using the constant is the best way to be compatible with multiple node versions. Well, worst-case I guess the @ts-ignore solution works, but...

[ZaneHannanAU]

Ugh… At this point I think we should deprecate most old/unused/otherwise broken versions…

[TheAkio]

This seems to be fixed with newer node typings. I'm using @types/node with version 10.14.5 and I don't get this error anymore, but I got the error with some 10.12.X typings.

EDIT: Looked into the repository a bit. The updated definitions for TypeScript 3.1 originally (later they moved it to the 3.2 folder) were added on Febuary 7th:

https://github.com/DefinitelyTyped/DefinitelyTyped/blob/77a6c2a9706e17d83a3623f2b1686aafa383e27b/types/node/ts3.1/util.d.ts

[orta]

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