inaccurate string type from json file while resolveJsonModule option on

[baivoom]

TypeScript Version: 3.1.1
VS Code Version: 1.28.1

Search Terms: resolveJsonModule

Code
./schema.json

{
    "type": "object"
}

./test.ts

import schema = require('./schema.json')
// give a restriction only the string value 'object' is acceptable
type Format = { type: 'object' } 
// here the vscode gives the following error
// ; Type { type: string } is not assignable to Format
// ;     Type 'string' is not assignable to  type ' "object" '
const data: Format  =  schema 

Expected behavior:
The imported string type from json file should be converted as:

From: { type: "object" }
To: type FromJson = { type: string & 'object' }

As a result, the code below should not be given warnings or errors:

// imported from json
type FromJson = { type: string & 'object' }
const json: FromJson = { type: 'object' }

// type restriction
type FromTs = { type: 'object' }

//  no error here
const ts: FromTs = json

// no side effect
type StringType = { type: string }
const acceptable: StringType = json

Actual behavior:
error on vscode, but pass the compilation

Others:
1
The typescript 3.03 does not give this error, but it is still not correct because it does not distinguish
{ type: 'object1' } from json and type { type: 'object'} from ts code.
2
just considering how to give the type from json file if the string value is very long
the type { type: string & 'this is a very very very very very very very very long'} seems ugly

Related Issues: Not found

[sheetalkamat]

Module type is always widened on import to that we aren't exposing private information in the json: eg. { name: "Some name", age: 55 } should be typed as { name: string, age: number }. This behavior is also same if for eg. you had js file instead of json with module.exports = { type: "object" }.

[baivoom]

I did not notice the design of "do not exposing private information". In this case, according to this design, the 'data-reflected' type exported whatever from the json or ts file will face the same problem, we can not give particular string values as type, for example, type Type = 'object'|'array'|'string', to restrict the input data . Does anyone have the alternative way to workaround?

[andykais]

came across this myself. I have many large json config files checked into a particular project, whos content is not sensitive. It is currently not possible to check those file's fields for string literals unless I check the files at runtime with ts-runtime. I want to be able to check the types of said files at compile time.

Perhaps a compiler flag like widenModuleTypes defaulted to true would be possible? If this is an intentional behavior it sounds like it is possible to change, just not desired as default behavior.

[typescript-bot]

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.