fix: isObject returns true for functions but docs say it should be false

[mkraenz]

Description

lib version used:
"0.14.1"

Minimal code-snippet showcasing the problem

jest test case

import { IsObject, isObject, validate } from 'class-validator';

it('BUG: isObject validates functions', () => {
  const fn = () => 'i am a function';

  expect(typeof fn).toBe('function');
  expect(isObject(fn)).toBe(false); // <<< this fails
});

class TestClass {
  @IsObject()
  public prop: unknown;
}

it('BUG: IsObject validates functions', async () => {
  const fn = () => 'i am a function';
  const subject = new TestClass();
  subject.prop = fn;

  expect(typeof subject.prop).toBe('function');
  const errors = await validate(subject);
  expect(errors).toEqual([]); // <<< this should fail but doesnt
});

Docs for @IsObject() read

Checks if the object is valid Object (null, functions, arrays will return false).

I assume

Expected behavior

I personally would expect isObject(fn) to return false.

Actual behavior

$ jest
 FAIL  src/class-validator-bug.spec.ts
  ✕ BUG: isObject validates functions (3 ms)
  ✓ BUG: IsObject validates functions (2 ms)

  ● BUG: isObject validates functions

    expect(received).toBe(expected) // Object.is equality

    Expected: false
    Received: true

       5 |
       6 |   expect(typeof fn).toBe('function');
    >  7 |   expect(isObject(fn)).toBe(false); // <<< this fails
         |                        ^
       8 | });
       9 |
      10 | class TestClass {

      at Object.<anonymous> (class-validator-bug.spec.ts:7:24)

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 passed, 2 total
Snapshots:   0 total
Time:        1.508 s, estimated 2 s
Ran all test suites.
error Command failed with exit code 1.

Investigation

class-validator/src/decorator/typechecker/IsObject.ts

Line 11 in 63fe9c5

return value != null && (typeof value === 'object' || typeof value === 'function') && !Array.isArray(value);

is the culprit.