fix: reset json pointer in merged allOf schema

[ivan-tymoshenko]

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Fix #481
Fix fastify/fastify#4092

#480 sets merged schema as a location, but doesn't set json pointer to the root of this merged schema.

[climba03003]

Will it be problem of deeply nested schema?

[ivan-tymoshenko]

It should work with nested schemas. Can you provide an example of what you mean?

[climba03003]

I get my answer when I create the example.
Here comes one problem related to previous fix.

Recursive $ref will be a problem when using allOf.
It may not be a good usage.

{
  $id: 'base',
  anyOf: [
    {
      type: 'object',
      allOf: [
        {
          properties: {
            a: {
              anyOf: [
                { const: 'A1' },
                { const: 'A2' }
              ]
            }
          }
        },
        {
          properties: {
            b: { const: 'B' }
          }
        },
        {
          properties: {
            c: {
              oneOf: [
                { $ref: 'base' },
                { type: 'null' }
              ]
            }
          }
        }
      ]
    }
  ]
}

{
    $id: 'base',
    type: 'object',
    allOf: [
      {
        properties: {
          a: {
            anyOf: [
              { const: 'A1' },
              { const: 'A2' }
            ]
          }
        }
      },
      {
        properties: {
          b: { const: 'B' }
        }
      },
      {
        properties: {
          c: {
            oneOf: [
              { $ref: 'base' },
              { type: 'null' }
            ]
          }
        }
      }
    ]
  }

[ivan-tymoshenko]

I guess we can fix this. But there are some other problems with merging schemas that we should also. We can't use deepMerge for merging. I was trying to make it better #453, but it's not enough. We can check how json-schema-merge-allof works.

In general, we have some places where we have troubles (if/then, oneOf, anyOf, allOf, type array), bc json schema format designed for validation and described input types and we use json schema for serialization and ask people to describe output types.

[ivan-tymoshenko]

I don't know another good library that uses json schema for serialization. @climba03003 @Eomm @mcollina If you know, please share a link. It will help in the design process.

[climba03003]

I think it worth an issue for discussion.

[climba03003]

LGTM.

[mcollina]

lgtm