Validation should not modify an object

[nrevutsky]

In case a schema has no validation item (anything is allowed), an object is modified after the validation

const schema ={
type: "object",
properties: {
name: { type: "string"}
value: {}
} 

obj = {name: "test", value: "v"}

after validation obj is
{name: "test", value: ["v"]}

[nrevutsky]

I created a test project https://codesandbox.io/p/devbox/j2t48z to show the cases when the parameter is modified inside the function. In case schema is used with middy validator request.event is modified before being processed by handler.

schema

{
  "type": "object",
  "additionalProperties": false,
  "required": [
    "body"
  ],
  "properties": {
    "body": {
      "type": "object",
      "additionalProperties": false,
      "required": [
        "filter"
      ],
      "properties": {
        "filter":{
          "type": "array",
          "minItems": 1,
          "uniqueItems": true,
          "items": {
            "oneOf": [
              {
                "type": "object",
                "additionalProperties": false,
                "required": [
                  "name", "condition", "value"
                ],
                "properties": {
                  "name": {
                    "type": "string"
                  },
                  "condition": {
                      "type": "string",
                      "enum": ["eq", "ne", "gt", "lt", "gte", "lte"]
                    },
                  "value": {}
                }
              },
              {
                "type": "object",
                "additionalProperties": false,
                "required": [
                  "name", "condition", "value"
                ],
                "properties": {
                  "name": {
                    "type": "string"
                  },
                  "condition": {
                      "type": "string",
                      "enum": ["in", "nin"]
                    },
                  "value": {
                    "type": "array",
                    "minItems": 1,
                    "uniqueItems": true,
                    "items": {}
                  }
                }
              }
            ]
          }
        }
      }
    }
  }
}

main

import eventSchema from './schemas/event.js'
import util from 'node:util';

util.inspect.defaultOptions.depth = null;

const testData = [
    {
        body: {
            filter: [{
                name: "aaa",
                condition: "eq",
                value: "Test 1"
            }]
        }
    },
    {
        body: {
            filter: [{
                name: "aaa",
                condition: "eq",
                value: 100
            }]
        }
    },
    {
        body: {
            filter: [{
                name: "aaa",
                condition: "eq",
                value: true
            }]
        }
    },
    {
        body: {
            filter: [{
                name: "aaa",
                condition: "in",
                value: ["test1", "test2"]
            }]
        }
    },
    {
        body: {
            filter: [{
                name: "aaa",
                condition: "in",
                value: ["test1"]
            }]
        }
    },
    {
        body: {
            filter: [{
                name: "aaa",
                condition: "in",
                value: [true]
            }]
        }
    },
    {
        body: {
            filter: [{
                name: "aaa",
                condition: "ne",
                value: null
            }]
        }
    },
]

const test = (data) => {
    const original = JSON.stringify(data, null, 2);
    const isValid = eventSchema(data);
    const after = JSON.stringify(data, null, 2);
    console.log({ isModified: original !== after, isValid, original: JSON.parse(original), after: JSON.parse(after), error: eventSchema.errors });
}

for (const data of testData) {
    test(data);
}

result

{
  isModified: true,
  isValid: true,
  original: {
    body: { filter: [ { name: 'aaa', condition: 'eq', value: 'Test 1' } ] }
  },
  after: {
    body: {
      filter: [ { name: 'aaa', condition: 'eq', value: [ 'Test 1' ] } ]
    }
  },
  error: null
}
{
  isModified: true,
  isValid: true,
  original: {
    body: { filter: [ { name: 'aaa', condition: 'eq', value: 100 } ] }
  },
  after: {
    body: {
      filter: [ { name: 'aaa', condition: 'eq', value: [ 100 ] } ]
    }
  },
  error: null
}
{
  isModified: true,
  isValid: true,
  original: {
    body: { filter: [ { name: 'aaa', condition: 'eq', value: true } ] }
  },
  after: {
    body: {
      filter: [ { name: 'aaa', condition: 'eq', value: [ true ] } ]
    }
  },
  error: null
}
{
  isModified: false,
  isValid: true,
  original: {
    body: {
      filter: [ { name: 'aaa', condition: 'in', value: [ 'test1', 'test2' ] } ]
    }
  },
  after: {
    body: {
      filter: [ { name: 'aaa', condition: 'in', value: [ 'test1', 'test2' ] } ]
    }
  },
  error: null
}
{
  isModified: false,
  isValid: true,
  original: {
    body: {
      filter: [ { name: 'aaa', condition: 'in', value: [ 'test1' ] } ]
    }
  },
  after: {
    body: {
      filter: [ { name: 'aaa', condition: 'in', value: [ 'test1' ] } ]
    }
  },
  error: null
}
{
  isModified: false,
  isValid: true,
  original: {
    body: {
      filter: [ { name: 'aaa', condition: 'in', value: [ true ] } ]
    }
  },
  after: {
    body: {
      filter: [ { name: 'aaa', condition: 'in', value: [ true ] } ]
    }
  },
  error: null
}
{
  isModified: true,
  isValid: true,
  original: {
    body: { filter: [ { name: 'aaa', condition: 'ne', value: null } ] }
  },
  after: {
    body: {
      filter: [ { name: 'aaa', condition: 'ne', value: [ null ] } ]
    }
  },
  error: null
}