Support serialized fields transforming

[kettanaito]

What

Add support to pre-format the serialized value of a field.

Why

This feature can be used in multiple scenarios:

1. Encrypt the entered password upon serialization (before sending/accessing the data).
2. Format date input value to match the desired date format.
3. General value normalization (casing, characters stripping)

How

• As a part of createField options (not preferable)
• Would be nice to have it as serialize method on the instance of a custom component wrapped in createField

Specification

General statements

1. Serialization formatting affects only the returned serialized value. It has no affect over the actual field's value, or field's state, in general.
2. It is possible to provide a custom serialization formatter in two ways:
   1. Upon the field's composition.
   2. As a dedicated prop to the field's instance.
3. When no custom formatter function is provided, a field's value is returned during the serialization (as it is now)

Syntax

type SerializeFunc<ValueType> = (value: ValueType) => ValueType

[kettanaito]

Draft

Specification

• Field's serialized value can be controlled using onSerialize prop of the respective field, or upon the field's construction via createField options.
• onSerialize prop accepts a function that returns the serialized field's value
• onSerialize function can return nothing, which makes the field skipped during the serialization

Usage

This:

export default createField({
  onSerialize({ value, fieldProps, fields, form }) {
    return value.replace(' ', '') // removes spaces
  }
})(Input)

This implies that all instances of Input field will have the provided serialized value transformer.

And this:

<Input
  name="fieldOne"
  value="some thing"
  onSerialize={({ value, fieldProps, fields, form }) => {
    return value.replace(' ', '') // removes spaces
  }} />

This implies that only this very Input field has the provided serialized value transformer.

Both declaration examples will be serialized into the following JSON:

{
  "fieldOne": "something"
}

[kettanaito]

• Need to adjust flattenDeep to properly handle plain objects. There is an issue with passing iterable instances, as it would iterate deeply through its private keys (i.e. __ID).

flattenDeep was removed. Used getLeavesWhich instead.