Issue type:

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

Database system/driver:

[ ] cordova
[ ] mongodb
[ ] mssql
[ ] mysql / mariadb
[ ] oracle
[ ] postgres
[ ] cockroachdb
[ ] sqlite
[ ] sqljs
[ ] react-native
[ ] expo
[x] all/not db specific
TypeORM version:

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

some times it's useful to have a common column settings object. It's good if you need some compatibility between different db's, or even just for plain readability.

const dbConf = {
  idColumn: {nullable: false, type: 'varchar', length: 36},
  json: {type: 'json', nullable: true},
  shortTextField: {type: 'varchar', length: 64},
  numeric: {type: 'int'}
}

//Entity1.ts
@Entity
export class Entity1 {
  @PrimaryColumn(dbConf.idColumn)
   id!: string;

  @Column(dbConf.shortTextField)
   someColumn: string;
}

//Entity2.ts
@Entity
export class Entity2 {
  @PrimaryColumn(dbConf.numeric)
   id: number;

  @Column(dbConf.idColumn)
   someIdColumn: string;
}

unfortunately, PrimaryColumn modifies the passed options, and now Entity2 will have a compound key, as dbConf.idColumn has changed to include primary: true.