Date format returned via REST API does not match model definition

[chris-greenlight]

Description/Steps to reproduce

Using Loopback 4. This is a simple model that uses a MySQL datasource.

The model field for the date is like this -- using string for date type, since MySQL will convert:

@property({ type: 'string', length: 100, id: false, required: true, }) thedate: string;

The create operation via REST API specified the date value like {"thedate": "2018-01-01"}

The value stored in the database (DATE type field) is exactly that, 2018-01-01

Later a GET for the same resource formats the date like Sun Jan 01 2018 20:00:00 GMT-0400 (Eastern Daylight Time)

Where is this conversion happening? How can I disable it?

The correct response is the same as the input: 2018-01-01

Additional information

node -e 'console.log(process.platform, process.arch, process.versions.node)'
darwin x64 10.10.0

npm ls --prod --depth 0 | grep loopback

├── @loopback/boot@1.0.1
├── @loopback/context@1.0.0
├── @loopback/core@1.0.0
├── @loopback/openapi-v3@1.0.1
├── @loopback/repository@1.0.1
├── @loopback/rest@1.0.1
├── @loopback/service-proxy@1.0.0
├── loopback-connector-mysql@5.3.1

Thank you

[marioestradarosa]

@property({
    type: 'date',
    default: () => new Date(),
  })
  thedate?: string;

will get "thedate": "2018-01-01T00:00:00.000Z", in RFC3339 see openAPI datatypes.

If you specify type: 'string' you will get the result in the format you specified above when opened the issue.

[bajtos]

TL;DR: I was able to reproduce the problem. The trick is to:

• use MySQL, not in-memory connector
• configure LoopBack property to have string type
• configure the database column to have DATE type

My conclusion is that we need to add support for DATE type to LoopBack4, which may require adding support for DATE type to loopback-datasource-juggler first.

The full story goes below.

---

Lets' investigate.

How does the in-memory connector work?

1. Added a thedate property as described above to our Todo example
2. Started the app, loaded API Explorer
3. Created a new Todo item with thedate: 2018-11-01. The response said thedate is 2018-11-01.
4. Fetched a list of all Todo items. The recently added item had thedate set to 2018-11-01.

All is good so far. Let's switch to MySQL.

1. npm install loopback-connector-mysql

2. Change datasources/db.datasource.json, set connector to mysql.

3. Edit datasources/db.datasource.js to overwrite the connector to require('loopback-connector-mysql') - this is a hack we already use elsewhere to overcome a known problem of the layout of dependencies in Lerna monorepos.

4. Implement a simple automigration script as described in Add the doc for datasource migration #1547.

   const {DbDataSource} = require('./dist/src/datasources/db.datasource.js');
   const {TodoRepository} = require('./dist/src/repositories/todo.repository.js');
   
   const db = new DbDataSource();
   const repo = new TodoRepository(db);
   
   db.automigrate(['Todo']).then(
     success => {
       console.log('database was succesfully updated');
       process.exit(0);
     },
     error => {
       console.error('cannot update the database', error);
       process.exit(1);
     }
   );

5. Run autoupdate with DEBUG=*. The output says that the following MYSQL query was executed:

   CREATE TABLE `Todo` (
     `id` INT(11) NOT NULL PRIMARY KEY,
     `title` VARCHAR(512) NOT NULL,
     `desc` VARCHAR(512) NULL,
     `isComplete` TINYINT(1) NULL,
     `remindAtAddress` VARCHAR(512) NULL,
     `remindAtGeo` VARCHAR(512) NULL,
     `thedate` VARCHAR(100) NOT NULL
   )

   Notice that thedate was created as VARCHAR(100)!

6. Start the app again and create a todo item with thedate set. Make sure to fill id too, because the database column id was not setup to be autogenerated! (This looks like a bug in loopback-connector-mysql's automigration.)

7. The property thedate is treated as a string in all responses (create, find all).

Let's try to change the MySQL column type from VARCHAR(100) to DATE.

1. Change the definition of thedate property as follows

   @property({
     type: 'string',
     id: false,
     required: true,
     mysql: {
       dataType: 'DATE',
     },
   })
   thedate: string;

2. Run automigration again. The column thedate is defined as follows:

   `thedate` DATE NOT NULL\n`
   

3. Create a new Todo item. The response contains thedate in the YYYY-MM-DD format (e.g. 2018-11-01).

4. List all Todo items via GET /todos. The response contains thedate formatted for humans: Thu Nov 01 2018 01:00:00 GMT+0100 (Central European Standard Time). 💥 💣 💥

[bajtos]

It looks like juggler does have some sort of support for DATE values via a DateString types, see loopbackio/loopback-datasource-juggler#1356, loopbackio/loopback-datasource-juggler#1365, the api docs and a possible bug loopbackio/loopback-datasource-juggler#1636.

I am not sure if DateString is a good solution for this problem to be honest, I was pretty skeptical about it from the beginning - see my comments in loopbackio/loopback-datasource-juggler#1356.

When I changed Todo example to define thedate property with type: 'DateString' and hacked repository-json-schema to understand this new type (map it to {type: 'string', format: 'date'}), I received the following value in the list of todos:

 "thedate": "2018-11-01T00:00:00.000Z"

Not what we wanted!

I think it will be best to define a new type to represent values values with a date part but no time part.

[bajtos]

Where is this conversion happening? How can I disable it?

AFAICT, the conversion is done by the mysql driver, see here: https://github.com/mysqljs/mysql/blob/ad014c82b2cbaf47acae1cc39e5533d3cb6eb882/lib/protocol/packets/RowDataPacket.js#L57-L87

Fortunately, this behavior can be disabled by setting the connector (LB dataSource) option dateStrings to true. Quoting from connector's README (see Connection Options):

dateStrings: Force date types (TIMESTAMP, DATETIME, DATE) to be returned as strings rather then inflated into JavaScript Date objects. Can be true/false or an array of type names to keep as strings. (Default:false)

I have verified that when I enable this option, the problem goes away. Just add the following line to your db.datasource.json and keep your thedate property defined as you have described at the top.

  "dateStrings": ["DATE"]

[bajtos]

I opened a new issue to keep track of implementing DATE as a new type in LoopBack - see #1966.

Let's keep this issue focused on helping @chris-greenlight to find a short-term workaround using what LB4 provides right now.

@chris-greenlight could you please enable dateStrings in your datasource config and confirm that it solves the problem?

[chris-greenlight]

Yes will try that and report back

…

On Fri, Nov 2, 2018 at 4:52 AM Miroslav Bajtoš ***@***.***> wrote: I opened a new issue to keep track of implementing DATE as a new type in LoopBack - see #1966 <#1966>. Let's keep this issue focused on helping @chris-greenlight <https://github.com/chris-greenlight> to find a short-term workaround using what LB4 provides right now. @chris-greenlight <https://github.com/chris-greenlight> could you please enable dateStrings in your datasource config and confirm that it solves the problem? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1948 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AmwxD-7I-_d26TQD-6a9UrwivTignmU0ks5urAfggaJpZM4YDBJR> .

[bajtos]

@chris-greenlight have you had a chance to try add dateStrings setting to your MySQL datasource config? Did it fix the issue?

[Riplar]

@bajtos do you know how to disable this behavior using a postgresql database? I wasn't able to find anything similiar to the "dateStrings" option in mysql for postgresql.

[bajtos]

@RipkensLar Our postgresql connector is using pg under the hood. I did a quick search and it looks like pg does not handle DATE values correctly - see the discussion in brianc/node-postgres#1844. I think that means you are out of luck :( Here are few more items that may be relevant: brianc/node-postgres#783, brianc/node-postgres#510 and other issues/pull-requests linked.

[stale]

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[stale]

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[pktippa]

Worked for me at Model property level Ex: person.model.ts

  @property({
    type: 'string',
    default: null,
    mysql: {
      dataType: 'DATE',
    },
  })
  date_of_birth: string;

In Datasource config

{
  name: 'db',
  connector: 'mysql',
  host: process.env.DB_HOSTIP ?? '127.0.0.1',
  port: 3306,
  user: process.env.DB_USER ?? 'root',
  password: process.env.DB_PASS ?? 'password',
  database: process.env.DB_NAME ?? 'db',
  dateStrings: ['DATE'], // added this as suggested by @bajtos 
}

[dansterrett]

This workaround worked for me: brianc/node-postgres#1844 (comment)

The solution is to override the parser for Date fields:

var types = require('pg').types
types.setTypeParser(types.builtins.DATE, (val) => val)