the lb4 datasource can't create a database automatically in mongoDB

[Barnette-ao]

Describe the bug

Desciption of the bug

when I want create a datasource to connect with mongoDB database,then I read the document ,I enter the lb4 datasource in the CLI. when I finish the creation of the datasource, the .datasource.ts file as follows:

const config = {
  name: 'db',
  connector: 'mongodb',
  url: 'mongodb://localhost:27017/testdb',
  host: 'loaclhost',
  port: 27017,
  user: '',
  password: '',
  database: 'testdb',
  useNewUrlParser: true
};

Expect

I expect after I finish the creation of the datasource,the testdb will automatically created in the MongoDB.

Actual

when I exeute the mongod.exe, and open the CLI, then
input：

show dbs

the output is :

3dcmsT     0.000GB
admin      0.000GB
config     0.000GB
local      0.000GB
vote_rule  0.001GB

there is no testdb as I expected!!!

what should I do to use lb4 datasource to connect the MongoDB server?

when I using loopback 3 to enter lb datasource ,the loopback will create the database automatically ,and I check the mongoDB,I also can see the new database when I define in the config.

but when I use loopback 4 to do the same thing,it is not work?!

It there angthing additional I should know to get my expection done ?

Logs

No response

Additional information

No response

Reproduction

https://codesandbox.io/s/nifty-wilson-4u0mdy

[achrinza]

LoopBack 4 does not perform auto-migration on every startup. On most projects ,npm run migrate can be used to run auto-update. The --rebuild flag can be used to perform a full, destructive auto-migrate.

See https://loopback.io/doc/en/lb4/Database-migrations.html and the scaffold-ed src/migrate.ts for more details.

[Barnette-ao]

OK,and I check the document again,and find that the repository is the essential part of connetor of mongoDB,as for when I use lb4 datasource to create a connector configuration file ,then it will indeed not create an database automatically!

and after I create a controller of a test model ,then I post an data instance of it.

as a result, when I check the db list in mongoDB CLI,the new database shows in the list.

in conclusion, the database will not create before there is no data record in it.