exception thrown when pick schema

[veyronfei]

code 1. ASchema = new SimpleSchema([{
  a: {
    type: String,
    custom: function() {},
  }
}]);

code 2. BSchema = ASchema.pick(['a']);

Because I don't need custom in BSchema, so I add a line:

code 3. BSchema._schema.a.custom = undefined;

But the following code4 will throw exception

code 4. CSchema = BSchema.pick(['a']);

Error: Invalid definition for a field.

But if I put code 3 below code 4, everything works fine.

May I ask why it throws an exception? and what is the best way to do code 3?

[aldeed]

The Meteor SimpleSchema package is no longer maintained other than critical fixes to keep it running with each latest Meteor release. Closing non-critical issues in this repo. Anyone who cares about this may do one or more of the following:

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