feat(input_schema): Allow nullable field default to null

[mfori]

Solves https://github.com/apify/apify-core/issues/20247

The default property should allow default: null if field has nullable: true

"test": {
    "title": "test",
    "description": "test",
    "type": "integer",
    "nullable": true, 
    "default": null
}

Thanks to unevaluatedProperties from draft 2019 it's quite easy now

[Copilot]

Pull Request Overview

This PR allows null values as defaults in input schema fields when the field has nullable: true. The implementation uses JSON Schema's unevaluatedProperties from draft 2019 to conditionally validate the default property type based on the nullable flag.

• Adds conditional validation that allows default: null when nullable: true
• Updates all property type definitions to use unevaluatedProperties instead of additionalProperties
• Adds comprehensive test coverage for nullable default behavior across all supported field types

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
test/input_schema.test.ts	Adds comprehensive test cases covering nullable default validation for all field types
packages/input_schema/src/schema.json	Updates JSON schema definitions to conditionally allow null defaults based on nullable property

[valekjo]

I'm surprised about the same thing as Copilot :D - that the if condition works even if the field is missing. I see the tests cover it and work though :)

[mfori]

I'm surprised about the same thing as Copilot :D - that the if condition works even if the field is missing. I see the tests cover it and work though :)

It's quite confusing but it must be like this, because the value fulfill the condition (schema)

"if": { "properties": { "nullable": { "const": false } } }

even if the nullable field is missing, because the field is not required. So the schema "properties": { "nullable": { "const": false } } say that the nullable field must be false if present, but doesn't have to be present.

On the other hand, if we would use the other one:

"if": { "properties": { "nullable": { "const": true } } }

This says that the nullable field is true or not present.

Working approach would be this:

  "if": {
    "properties": { "nullable": { "const": true } },
    "required": ["nullable"]
  },

but it works the same as current solution.