Declare a type with a JSON file instead of an interface

[ORESoftware]

Search Terms

typescript json interface file

Suggestion

I have this question on SO:
https://stackoverflow.com/questions/50181254/static-typing-with-json-and-typescript?noredirect=1#comment87380729_50181254

Why can't we declare a TS type based on a .json file? Something like this:

export type MyInterface = typeof 'path/to/json/file.json'

it seems like a no-brainer to me, but maybe I am stupid.

Use Cases

Keep things DRY. Use JSON files as interfaces.

Examples

Done did.

Checklist

My suggestion meets these guidelines:
[x] This wouldn't be a breaking change in existing TypeScript / JavaScript code
[x] This wouldn't change the runtime behavior of existing JavaScript code
[x] This could be implemented without emitting different JS based on the types of the expressions
[x] This isn't a runtime feature (e.g. new expression-level syntax)

[mhegazy]

You are in luck! #22167 just got merged, and with --resolveJsonModule you can load the json object in your program and use its type..

with import types too you can capture that type in a type alias:

type schemaType = typeof import("./schema.json");

[ORESoftware]

nice that is cool, how do we know when the next tsc version will be published on NPM? is there some notification system?

[mhegazy]

It is published nightly around midnight PST

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.

[ORESoftware]

@mhegazy one potential improvement!

tsc can now use .json files for types - but can tsc use json-schema files to determine generic types?

for example, say I have this JSON file:

{
  "foo":"bar"
}

now, foo the interface for the above could be:

interface JSON {
  foo: "bar"
}

or it could be:

interface JSON {
  foo: string
}

which does tsc currently do? Could tsc be updated to handle json-schema from
http://json-schema.org/

?

[ORESoftware]

@mhegazy what about importing json files and getting type info? If I do:

import json = require('../../my.json')

and also use:

"resolveJsonModule": true,

in my tsconfig.json. My project no longer compiles correctly. Is this a known problem? Should I file a new ticket?

[mhegazy]

Should I file a new ticket?

yes please.

[ORESoftware]

@mhegazy thanks, I filed the issue here: #25216