I have the following yaml file:

trainingPhrases:
- help me
- what to do
- how to play
- help

I readi it from disk using readFile from node and parse it using load from js-yaml:

import { load } from "js-yaml";
import { readFile } from "fs/promises";

const phrases = load(await readFile(filepath, "utf8")).trainingPhrases as string[];

I get the following eslint warning:

ESLint: Unsafe member access .trainingPhrases on an any value.(@typescript-eslint/no-unsafe-member-access)

Instead of suppressing the warning, I would like to map it into a concrete type for the YAML file (as it happens in axios for example: axios.get<MyResponseInterface>(...) - performs a GET and MyResponseInterface defines the structure of the HTTP response).

Is there a dedicated library for that?

I have the following yaml file:

trainingPhrases:
- help me
- what to do
- how to play
- help

I readi it from disk using readFile from node and parse it using load from js-yaml:

import { load } from "js-yaml";
import { readFile } from "fs/promises";

const phrases = load(await readFile(filepath, "utf8")).trainingPhrases as string[];

I get the following eslint warning:

ESLint: Unsafe member access .trainingPhrases on an any value.(@typescript-eslint/no-unsafe-member-access)

Instead of suppressing the warning, I would like to map it into a concrete type for the YAML file (as it happens in axios for example: axios.get<MyResponseInterface>(...) - performs a GET and MyResponseInterface defines the structure of the HTTP response).

Is there a dedicated library for that?

• javascript
• typescript
• types
• yaml

• What do you mean by "concrete type for the YAML file (as it happens in axios for example)."? – Yoshi Commented Jun 28, 2021 at 8:19
• @Yoshi that I define structure as interfaces in TS - in axios it looks like: axios.get<MyResponseInterface>(...) where MyResponseInterface is interface defined by me and it reflects structure of the response – pixel Commented Jun 28, 2021 at 9:06
• I'm not used to the node functions, so I can't say if say accept a type parameter. But you could simply declare phrases to be of the correct type. Have you tried that? E.g. const phrases: YourType = .... (At least I'm assuming it's node, otherwise, you'd need to explain where load and readFile are from). – Yoshi Commented Jun 28, 2021 at 9:07
• @yoshi I added imports – pixel Commented Jun 28, 2021 at 9:37

1 Answer 1

From what I can see when using @types/js-yaml is that load is not generic, meaning it does not accept a type parameter.

So the only way to get a type here is to use an assertion, for example:

const yaml = load(await readFile(filepath, "utf8")) as YourType;
const phrases = yaml.trainingPhrases;

Or in short:

const phrases = (load(await readFile(filepath, "utf8")) as YourType).trainingPhrases;

If you absolutely want a generic function, you can easily wrap the original, like:

import {load as original} from 'js-yaml';

export const load = <T = ReturnType<typeof original>>(...args: Parameters<typeof original>): T => load(...args);

And then you can use it as:

const phrases = load<YourType>('....').trainingPhrases;