[core] support conditional storage

[wxhccc]

Sometimes we need to use a path to determine whether another path needs to be persisted, so I suggest to expanding the options.paths

type CheckStateProp = (store: PiniaPluginContext['store']) => boolean
type PropPath = string | [string, CheckStateProp]


...
// when use
paths: ['a', ['b', (store) => store.a === true]]

if a is true, b will persisted, otherwise not persisted b

[prazdevs]

Hi, i'm still considering adding per-path persistence config as suggested in #19 , could that be part of it, a per-path like this:

persist: [
{
  path: 'a'
},
{
  path: 'b',
  persist: (store) => store.a === true
}
]

or smth like that

This would be part of a V2, for advanced use

[wxhccc]

it's all right. but I don't think it is good way. for example:

persist: [
{
  path: 'a',
  beforeRestore: () => {},
  afterRestore: () => {},
  serializer: {
    serialize: JSON.stringify,
    deserialize: JSON.parse,
  }
},
{
  path: 'b',
  persist: (store) => store.a === true,
  beforeRestore: () => {},
  afterRestore: () => {},
  serializer: {
    serialize: JSON.stringify,
    deserialize: JSON.parse,
  }
}
]

i need to pass other properties in every item. zhuzhengshou want to to separate state values to localstorage and sessionstorage at the same time when state change.

[prazdevs]

hmm i see what you mean, i kinda saw a good opportunity as both feature ideas are linked to per-path config

[prazdevs]

ok i may have an exampls that could help you?

    persist: {
      serializer: {
        deserialize: JSON.parse,
        serialize: (state) => {
          const { a, b } = state
          const toStore = a ? { a, b } : { a }
          return JSON.stringify(toStore)
        }
      }
    },

You can use the serializer to define conditions for elements to be persisted or not. I think that's the best way to do it without adding "too much" to the plugin :)

Let me know if that helped

[wxhccc]

ok i may have an exampls that could help you?

    persist: {
      serializer: {
        deserialize: JSON.parse,
        serialize: (state) => {
          const { a, b } = state
          const toStore = a ? { a, b } : { a }
          return JSON.stringify(toStore)
        }
      }
    },

You can use the serializer to define conditions for elements to be persisted or not. I think that's the best way to do it without adding "too much" to the plugin :)

Let me know if that helped

yes, it works. but if i need to use custom serializer to do some complex questions, I prefer write a local pinia plugin to do this.

[prazdevs]

You can always define an external function that returns the state to store from the current state, and have concerns separated this way.

[prazdevs]

Closing this as it has a workaround, and probably won't see an implementation in the current situation. Feel free to propose new stuff :)