Exact JSON schema downgrading.

[samchon]

Found some JSON schema downgrade bugs.

Nested oneOf in the oneOf type

When oneOf type is referencing another oneOf type that is caplused in the components.schema as named schema, JSON schema downgraders had defined nested oneOf type under an oneOf type.

This PR fixes the bug, so that below test code works from now on.

export const test_llm_schema_union = (): void => {
  const components: OpenApi.IComponents = {
    schemas: {
      named: {
        oneOf: [
          {
            const: 4,
          },
          {
            const: 5,
          },
        ],
      },
    },
  };
  const schema: OpenApi.IJsonSchema = {
    oneOf: [
      {
        const: 3,
      },
      {
        $ref: "#/components/schemas/named",
      },
    ],
  };

  const llm: ILlmSchema | null = HttpLlm.schema({
    components,
    schema,
  });
  TestValidator.equals("union")(llm)({
    type: "number",
    enum: [3, 4, 5],
  });
};

Double nested $ref type is nullable case

When nullable type is nested in the $ref type, JSON schema downgrader could not detect it properly. This PR fixes the bug, so that makes below test function to be worked properly.

export const test_json_schema_downgrade_v30_nullable = (): void => {
  const original: OpenApi.IComponents = {
    schemas: {
      union: {
        oneOf: [
          {
            type: "null",
          },
          {
            type: "string",
          },
          {
            type: "number",
          },
        ],
      },
    },
  };
  const components: OpenApiV3.IComponents = {
    schemas: {},
  };
  const schema: OpenApiV3.IJsonSchema = OpenApiV3Downgrader.downgradeSchema({
    original,
    downgraded: components,
  })({
    oneOf: [
      {
        type: "boolean",
      },
      {
        $ref: "#/components/schemas/union",
      },
    ],
  } satisfies OpenApi.IJsonSchema);
  TestValidator.equals("nullable")({
    components,
    schema,
  })({
    components: {
      schemas: {
        "union.Nullable": {
          oneOf: [
            {
              type: "string",
              nullable: true,
            },
            {
              type: "number",
              nullable: true,
            },
          ],
        },
      },
    },
    schema: {
      oneOf: [
        {
          type: "boolean",
          nullable: true,
        },
        {
          $ref: "#/components/schemas/union.Nullable",
        },
      ],
    },
  });
};

[samchon]

OK, no problem may be.