DataVersion: Type safe data migrations

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Versions [RSS] 0.1.0.0, 0.1.0.1
Change log ChangeLog.md
Dependencies base (>=4.7 && <5), generic-lens, microlens [details]
License MIT
Copyright 2019 Sandy Maguire, James King
Author Sandy Maguire, James King
Maintainer james@agentultra.com
Category Data
Home page https://github.com/agentultra/DataVersion#readme
Bug tracker https://github.com/agentultra/DataVersion/issues
Source repo head: git clone https://github.com/agentultra/DataVersion
Uploaded by agentultra at 2022-11-30T21:04:20Z
Distributions NixOS:0.1.0.1
Downloads 604 total (8 in the last 30 days)
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Status Docs available [build log]
Last success reported on 2022-11-30 [all 1 reports]

Readme for DataVersion-0.1.0.1

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DataMigration

Hackage

Type safe data migrations.

All you need to do is create a type family to index your record and provide an instance of Transform to migrate your data between versions.

Migrations are type-safe and the library uses generics to remove as much boiler-plate as possible.

Examples

data family Foo (version :: Nat)

newtype MyString = MyString { unMyString :: String }
   deriving (IsString, Show, Eq)

data instance Foo 0
  = FooV0
    { _fooId :: Int
    , _fooName :: String
    }
  deriving (Generic, Show, Eq)

data instance Foo 1
  = FooV1
  { _fooId        :: Int
  , _fooName      :: MyString
  , _fooHonorific :: String
  }
  deriving (Generic, Show, Eq)

instance Transform Foo 0 where
  up   v = genericUp   v (const "esquire") (const MyString)
  down v = genericDown v (const unMyString)


spjV0 :: Foo 0
spjV0 = FooV0 1 "Simon PJ"


spjV1 :: Foo 1
spjV1 = up spjV0

-- spjV1 = FooV1 1 (MyString "Simon PJ") "esquire"

Future Considerations

In the future this library will provide a high-level DSL to enable better ergonomics around type errors so that you can see which fields require specification in the migration.