Loopback-next: Use \d in AJV pattern doesn't work

[dhmlau]

Steps to reproduce

When creating a model, I'd like to specify a pattern for my phoneNum property, so I have:

  @property({
    type: 'string',
    jsonSchema: {
      pattern: '\d{3}-\d{3}-\d{4}',
      // pattern: '^[0-9()\\-\\.\\s]+$'
    },
  })
  phoneNum?: string;

There are actually 2 problems:

Problem 1
If I have pattern: '\d{3}-\d{3}-\d{4}', and hit save, it turns into:

pattern: 'd{3}-d{3}-d{4}',

Notice the \ got removed. Not knowing a better solution, I disable prettier by adding *.ts in .prettierignore.

If it's within the quotes, should the string be treated as-is? (It's likely not a LB issue).

Problem 2
Given the pattern above, I was hoping it accepts 111-111-1111 as the phone number. But I got the following error in API Explorer:

{
  "error": {
    "statusCode": 422,
    "name": "UnprocessableEntityError",
    "message": "The request body is invalid. See error object `details` property for more info.",
    "code": "VALIDATION_FAILED",
    "details": [
      {
        "path": ".phoneNum",
        "code": "pattern",
        "message": "should match pattern \"d{3}-d{3}-d{4}$\"",
        "info": {
          "pattern": "d{3}-d{3}-d{4}$"
        }
      }
    ]
  }
}

Also noticed the removed \.

I can verify that the AJV pattern is taking effect, because if i change the pattern to something else (e.g. '^[0-9()\\-\\.\\s]+$', it works fine. The problem happened when there's \d.

[dhmlau]

@raymondfeng @jannyHou , you are more familiar with AJV, do you know what could be the issue? Thanks.

[bajtos]

pattern: 'd{3}-d{3}-d{4}',

IIUC, you are trying to create a regular string and use \d as an escape sequence similar to \n. I suspect that \d is not a valid sequence, therefore Prettier is converting it to d, because that's what the JavaScript runtime is going to do anyways. You can try this yourself:

$ node
> '\d{2}'
'd{2}'

I think you need to use double backslash as follows:

$ node
> new RegExp('\\d{2}')
/\d{2}/

Here is the fixed property definition:

  @property({
    type: 'string',
    jsonSchema: {
      pattern: '\\d{3}-\\d{3}-\\d{4}',
      // pattern: '^[0-9()\\-\\.\\s]+$'
    },
  })
  phoneNum?: string;

It would be nice if @property decorator supported regular expressions in jsonSchema.pattern field:

  @property({
    type: 'string',
    jsonSchema: {
      pattern: /\d{3}-\d{3}-\d{4}/,
    },
  })
  phoneNum?: string;

Until then, you can use .source property of regular expressions.

pattern: /\d{3}-\d{3}-\d{4}/.source,

[dhmlau]

Thanks @bajtos . Double backslash works for me. i.e.

jsonSchema: {
      pattern: '\\d{3}-\\d{3}-\\d{4}',
    },

[bajtos]

I created a new issue to improve UX around jsonSchema.pattern - see https://github.com/strongloop/loopback-next/issues/4228