Issue type:

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

Database system/driver:

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

TypeORM version:

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

Local development against a default install of MySQL8 Community Edition.

@Entity("metadataversion")
export class metadataversion {

    @Column({
        primary: true,
        nullable: false,
        type: "varchar",
        length: 255,
        name: "MetaDataVersionOID",
        asExpression: "concat('MDV.',upper(replace(`Name`,' ','')))",
        generatedType: "STORED"
    })
    MetaDataVersionOID: string;

    @Column("varchar", {
        nullable: false,
        length: 45,
        name: "Name"
    })
    Name: string;
}

I have synchronize: true in my config.

When starting the server, typeorm will alter the MetaDataVersionOID column every time:

[0] query: ALTER TABLE metadataversion CHANGE MetaDataVersionOID MetaDataVersionOID varchar(255) AS (concat('MDV.',upper(replace(Name,' ','')))) STORED NOT NULL

To try and see why typeorm was thinking this column was different, I went into driver/mysql/MysqlDriver.js and uncommented out line 641:

console.log("asExpression:", tableColumn.asExpression, columnMetadata.asExpression);

When I run now, typeorm logs the following:

[0] asExpression: concat(_utf8mb3\'MDV.\',upper(replace(`Name`,_utf8mb3\' \',_utf8mb3\'\'))) concat('MDV.',upper(replace(`Name`,' ','')))

I tried modifying my expression to include the additional info to make them match like so:

    @Column({
        primary: true,
        nullable: false,
        type: "varchar",
        length: 255,
        name: "MetaDataVersionOID",
        asExpression: "concat(_utf8mb3\\'MDV.\\',upper(replace(`Name`,_utf8mb3\\' \\',_utf8mb3\\'\\')))",
        generatedType: "STORED"
    })
    MetaDataVersionOID: string;

This works when the table already exists; I no longer see any ALTER statement. However, when creating the table when it doesn't exist, it looks like typeorm adds more escapes and I end up with an expression like:

"concat(_utf8mb3\\\'MDV.\\\',upper(replace(`Name`,_utf8mb3\\\' \\\',_utf8mb3\\\'\\\')))"

Which MySQL fails on.

Not a huge issue as the alters don't result in any data loss and we will have synchronize: false set for production, but any ideas here? Thanks!