DataTypeNotSupportedError when using "| null" type

Issue type:

[x] bug report

Database system/driver:

[x] mysql

TypeORM version:

[x] latest

Steps to reproduce or a small repository showing the problem:

When I set one of my entity fields with | null, ex:

@Column({ name: "code", nullable: true })
public code?: string | null;

I am told

DataTypeNotSupportedError: Data type "Object" in "User.code" is not supported by "mysql" database.
    at new DataTypeNotSupportedError (/project/node_modules/typeorm/error/DataTypeNotSupportedError.js:16:28)
    at /project/node_modules/typeorm/metadata-builder/EntityMetadataValidator.js:73:27
    at Array.forEach (<anonymous>)
    at EntityMetadataValidator.validate (/project/node_modules/typeorm/metadata-builder/EntityMetadataValidator.js:70:36)
    at /project/node_modules/typeorm/metadata-builder/EntityMetadataValidator.js:41:74
    at Array.forEach (<anonymous>)
    at EntityMetadataValidator.validateMany (/project/node_modules/typeorm/metadata-builder/EntityMetadataValidator.js:41:25)
    at Connection.buildMetadatas (/project/node_modules/typeorm/connection/Connection.js:515:33)
    at Connection.<anonymous> (/project/node_modules/typeorm/connection/Connection.js:162:30)
    at step (/project/node_modules/typeorm/connection/Connection.js:32:23)

This is a problem for me as I use strictNullChecks (so ? only allows undefined) and use the difference as:

• null === the field is null
• undefined === i dont know the value of this field

[pleerock]

You need provide a data type explicitly. By default typeorm reads typeorm from type definition, e.g. : string, and string is reflected into String. But string|null is reflected into Object and we cannot determine type. So, what you should do is to specify type explicitly:

@Column({ type: "string", name: "code", nullable: true })
public code?: string | null;

[feimosi]

"text" type worked for me

@Column({ type: 'text', nullable: true })
content!: string | null;