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Bug Description

TypeScript inferred types: findAll incorrectly fails type-checking when using null as the value for a nullable field in the where clause.

If we skip type-checking, the query runs fine and returns the expected result.

Reproducible Example

Here is the link to the SSCCE for this issue: sequelize/sequelize-sscce#278

This is a type-checking issue and I'm not sure how to write a unit test asserting that a term type-checks, so I expect the SSCCE to pass testing with Postgres.

What do you expect to happen?

Given a model with a nullable array attribute:

class Foo extends Model<InferAttributes<Foo>, InferCreationAttributes<Foo>> {
  // ...
  
  @Attribute(DataTypes.ARRAY(DataTypes.STRING))
  declare colors?: Array<string>
}

Then null should be included in that attribute's type for the where-clause of a query.

// Works fine, doesn't type-check
const result = Foo.findAll({
  where: {
    colors: null
  }
})

What is actually happening?

The findAll call returns the correct results, but fails type checking because the type of where.colors does not include null:

No overload matches this call.
  Overload 1 of 2, '(this: ModelStatic<Foo>, options: Omit<FindOptions<InferAttributes<Foo, { omit: never; }>>, "raw"> & { raw: true; }): Promise<...>', gave the following error.
    Type '{ colors: null; }' is not assignable to type 'WhereOptions<InferAttributes<Foo, { omit: never; }>>'.
      Types of property 'colors' are incompatible.
        Type 'null' is not assignable to type 'WhereAttributeHashValue<string[] | undefined>'.
  Overload 2 of 2, '(this: ModelStatic<Foo>, options?: FindOptions<InferAttributes<Foo, { omit: never; }>> | undefined): Promise<...>', gave the following error.
    Type '{ colors: null; }' is not assignable to type 'WhereOptions<InferAttributes<Foo, { omit: never; }>>'.
      Types of property 'colors' are incompatible.
        Type 'null' is not assignable to type 'WhereAttributeHashValue<string[] | undefined>'. ts(2769)
  model.d.ts(104, 3): The expected type comes from property 'where' which is declared here on type 'Omit<FindOptions<InferAttributes<Foo, { omit: never; }>>, "raw"> & { raw: true; }'

Environment

• Sequelize version: @sequelize/core 7.0.0-alpha.41
• Node.js version: v20.14.0
• If TypeScript related: TypeScript version: typescript 5.4.5
• Database & Version: PostgreSQL 16
• Connector library & Version: pg 8.12.0

Would you be willing to resolve this issue by submitting a Pull Request?

• Yes, I have the time and I know how to start.
• Yes, I have the time but I will need guidance. Mostly just a nudge in the right direction for how the WhereAttributeHashValue type is constructed.
• No, I don't have the time, but my company or I are supporting Sequelize through donations on OpenCollective.
• No, I don't have the time, and I understand that I will need to wait until someone from the community or maintainers is interested in resolving my issue.

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