json-schema: v6 and v7 changed to better comply with the draft definitions.

[afinch7]

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• Add or edit tests to reflect the change. (Run with npm test.)
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• Avoid common mistakes.
• Run npm run lint package-name (or tsc if no tslint.json is present).

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If changing an existing definition:

• Provide a URL to documentation or source code which provides context for the suggested changes: https://json-schema.org/draft-06/schema#
  https://json-schema.org/draft-07/schema#

"type": ["object", "boolean"]

[typescript-bot]

@afinch7 Thank you for submitting this PR!

🔔 @bcherny @cyrilletuzi @LucianBuzzo @rolandjitsu - please review this PR in the next few days. Be sure to explicitly select Approve or Request Changes in the GitHub UI so I know what's going on.

If no reviewer appears after a week, a DefinitelyTyped maintainer will review the PR instead.

[cyrilletuzi]

@afinch7 What is the motivation of this PR? I don't see what it adds except refactoring, and I'm not confident in validating the changes, change from interface to type could have side effects.

[rolandjitsu]

@cyrilletuzi I second that. I cannot see how a schema object can be a boolean, at least not the root schema object.

[afinch7]

According to the draft 07 and 06 specs any field that can be a schema object can be a boolean as well.

Note this declaration in the 07 and 06 schemas. (see http://json-schema.org/draft-07/schema# and http://json-schema.org/draft-06/schema#)

"type": ["object", "boolean"]

This means that a schema like this

{
  "type": "object",
  "properties": {
    "aProp": false
  }
}

while mostly pointless is still valid, and more importantly

{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "aProp": false
  }
}

is valid.

I could have changed the definition of additionalProperties to be "boolean | JSONSchema6/7", but this doesn't correctly reflect the schema definition.

TL;DR;
The "additionalProperties" property was not functioning correctly before. Allowing for Schemas to be bools as well should better reflect the underlying spec, and fix this issue.

[afinch7]

@cyrilletuzi As for the interface to type change. I do see the potential for problems.
I.E.

class SomeClass implements JSONSchema7 

This will no longer compile.

I see there being two options to resolve this. Make this a breaking change or refactor this change to something like

type JSONSchemaSomething7 = JSONSchema7  | boolean;

interface JSONSchema7 {
  properties: JSONSchemaSomething7;
}

There may be a better way to refactor that not sure. What do you think?

[rolandjitsu]

@afinch7 I'm aware of that, but making the root schema a boolean makes no sense, especially when you're extending the interface or implementing it.

Your second suggestion would work though.

[afinch7]

Alright I created a test for the class implementation cases and
renamed my new type to JSONSchema6Definition and JSONSchema7Definition.
afinch7/DefinitelyTyped@0d7ab87

[rolandjitsu]

LGTM

[typescript-bot]

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