autoValue in SimpleSchema for update does not set given value

Question

I am using below field in SimpleSchema,

  "fileNo": {
    type: String,
    label: "File No.",
    autoValue: function() {
      console.log('this', this);
      console.log('typeof this.value.length ', typeof this.value.length);
      console.log('this.value.length ', this.value.length, this.value.length === 0, this.value.length == 0);
      console.log('this.value ', this.value, typeof this.value);
      console.log('this.operator ', this.operator);
      console.log('this.isSet ', this.isSet);
            if ( this.isSet && 0 === this.value.length ) {
                console.log('if part ran.');
                return "-";
            } else {
              console.log('else part ran.');
            }
        },
    optional:true
  },

I am using autoform to update a field. The problem is when I am updating the field with empty string (ie keeping textbox empty) , the value - is not set as per field definition in SimpleSchema code above.

I get logs as below,

clients.js:79 this {isSet: true, value: "", operator: "$unset", unset: ƒ, field: ƒ, …}
clients.js:80 typeof this.value.length  number
clients.js:81 this.value.length  0 true true
clients.js:82 this.value   string
clients.js:83 this.operator  $unset
clients.js:84 this.isSet  true
clients.js:86 if part ran.
clients.js:79 this {isSet: true, value: "-", operator: "$unset", unset: ƒ, field: ƒ, …}
clients.js:80 typeof this.value.length  number
clients.js:81 this.value.length  1 false false
clients.js:82 this.value  - string
clients.js:83 this.operator  $unset
clients.js:84 this.isSet  true
clients.js:89 else part ran.    

and my collection document does not have field fileNo .

What am I missing? all I want is when value of fileNo is empty/undefined value must be set to - (hyphen) . In document it must look like fileNo : "-"

Answer 1

You should handle 2 situations:

1. Document insert with empty (undefined) value for fileNo .

2. Document update with empty value for fileNo .

In second case, validator will try to remove the field from the document if its value is empty string ( optional: true ). We can catch and prevent this.

  fileNo: {
    type: String,
    label: 'File No.',
    autoValue() {
      if (this.isInsert && (this.value == null || !this.value.length)) {
        return '-';
      }
      if (this.isUpdate && this.isSet && this.operator === '$unset') {
        return { $set: '-' };
      }
    },
    optional: true
  }

Added : documentation used to write this answer (code works as expected; tested locally):

• aldeed:meteor-collection2#autovalue

• aldeed:meteor-simple-schema#autovalue