MariaDb VIRTUAL columns don't accept [NULL | NOT NULL]

[StrikeForceZero]

Issue type:

[ ] question
[x] bug report
[ ] feature request
[ ] documentation issue

Database system/driver:

[ ] cordova
[ ] mongodb
[ ] mssql
[x] mysql / mariadb
[ ] oracle
[ ] postgres
[ ] sqlite
[ ] sqljs
[ ] react-native
[ ] expo

TypeORM version:

[ ] latest
[ ] @next
[x] 0.2.7 (or put your version here)

Steps to reproduce or a small repository showing the problem:

import {
    Column,
    Entity,
    PrimaryColumn,
} from 'typeorm';

@Entity()
export class Foo {
    @PrimaryColumn()
    public id: number;

    @Column({
        name: 'ipv4_bin',
        type: 'varbinary',
        length: 16,
    })
    public ipv4_bin: string;

    @Column({
        name: 'ipv4_text',
        type: 'varbinary',
        length: 16,
        asExpression: 'INET_NTOA(ipv4_bin)',
        generatedType: 'VIRTUAL',
    })
    public readonly ipv4_text: string;
}

This more or less creates this schema:

CREATE TABLE `foo` (
  `id`        int                                            NOT NULL,
  `ipv4_bin`  varbinary(16)                                  NOT NULL,
  `ipv4_text` varbinary(16) AS (INET_NTOA(ipv4_bin)) VIRTUAL NOT NULL,
  PRIMARY KEY (`id`)
)

The issue is https://github.com/typeorm/typeorm/blob/master/src/driver/mysql/MysqlQueryRunner.ts#L1500-L1503
adds the [NULL | NOT NULL] on a virtual column, which is fine in MySQL 5.7, but apparently not in mariaDB... I can't find anything hinting this in their documentation. Only Errors and articles saying so.

https://mariadb.com/kb/en/library/generated-columns/

https://www.percona.com/blog/2016/03/04/virtual-columns-in-mysql-and-mariadb/

You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'NOT NULL, PRIMARY KEY (`id`)'

Adding a check to the lines I referred to above

if (!(isMariaDb && column.asExpression) && !column.isNullable)
            c += " NOT NULL";
if (!(isMariaDb && column.asExpression) && column.isNullable)
            c += " NULL";

seems to work fine.

While the handling of VIRTUAL [NULL | NOT NULL] should probably need to be confirmed by mariaDb and documented, its current iteration doesn't allow it.

[ceteras]

This issue affects creating geometry virtual columns. A spatial index cannot be created for them as it requires a geometry NOT NULL definition.