Convert json schema draft 06 const values to typescript const values

[djbeaumont]

Resolves #263

I'm a little unclear on the structure of the project so any feedback on the PR is gratefully received. This is a little exploratory and I have no idea if this can be said to implement the feature from json schema draft 06, but I think it covers enough for my needs.

[nicojs]

Awesome! Open source at it's finest 👍. I like the simplicity of the solution.

The simple example now works:

export interface Foo {
  bar: true;
}

However, it seems that falsy values don't work yet 😈.

{
  "title": "Foo",
  "required": ["bar", "baz", "qux", "quux"],
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "bar": {
      "const": false
    },
    "baz": {
      "const": ""
    },
    "qux": {
      "const": 0
    },
    "quux": {
      "const": null
    }
  }
}

This results in:

export interface Foo {
  bar: {
    [k: string]: any;
  };
  baz: {
    [k: string]: any;
  };
  qux: {
    [k: string]: any;
  };
  quux: {
    [k: string]: any;
  };
}

[nicojs]

I'll see your PR and I'll raise you another PR

The falsy value thingy should be fixed in djbeaumont#1

🤟

[djbeaumont]

ahh great catch, thank you!

[djbeaumont]

@bcherny what do you think of this? I suppose it would have to be a new major version as it will be a big change to the outputted types.

[nicojs]

@bcherny I don't want to be rude, but could you please take a look? I would like to actually use it at our company. Thanks!

[qzb]

@nicojs Unfortunately bcherny maintains this package pretty unfrequently, I guess he'll accept this PR, but it could take a while.

[djbeaumont]

@nicojs FWIW I'm using this workaround in my codebase:

/**
 * Workaround until this is merged:
 * https://github.com/bcherny/json-schema-to-typescript/pull/264
 * @param {string} definition
 * @returns {string} Same defined interface with event_type made constant.
 */
function fudgeEventTypeInDefinition(eventType, definition) {
  const toReplace = 'event_type: string;';
  const replaceWith = `event_type: '${eventType}';`;
  return definition.replace(toReplace, replaceWith);
}

It works because the constant property I want to set happens to be the same as the filename of the schema that I'm parsing. Clearly not a general solution.

[qzb]

@djbeaumont According to JSON Schema const is only a shorthand for enum with single element, so if you can modify original JSON Schema file, simply replace "const": "value" with "enum": [ "value" ]. Enums are handled correctly by json2ts, so it should workaround your issue.

[bcherny]

Hey there @djbeaumont! Thanks for the contribution, and sorry about the delay in reviewing it.

Since const is just sugar for a single-member enum, could we try to implement this as normalizer step instead that de-sugars const to enum?

[bcherny]

Requesting changes per my comment above^

[JonathanWilbur]

@djbeaumont I can't wait for this to make it in. Thank you so much for pursuing this! Do you expect to follow up soon with corrections so this can be merged in?

[jeffvandyke]

What's the status on this? I found myself wanting to use "const", and while single-member "enum" works, I'd be excited to see this make it in!

[L2jLiga]

Hi there? Any updates upcomming here?

[bcherny]

#290 is another shot at this, using the normalizer approach.