https://github.com/jonathanjouty/aeson-possible

Three-valued types for use with aeson. Useful for use in PATCH endpoints.
https://github.com/jonathanjouty/aeson-possible

aeson

Last synced: over 1 year ago
JSON representation

Three-valued types for use with aeson. Useful for use in PATCH endpoints.

• Host: GitHub
• URL: https://github.com/jonathanjouty/aeson-possible
• Owner: jonathanjouty
• License: bsd-3-clause
• Created: 2023-12-19T19:30:52.000Z (over 2 years ago)
• Default Branch: main
• Last Pushed: 2024-01-23T13:40:14.000Z (over 2 years ago)
• Last Synced: 2024-04-25T23:02:21.070Z (about 2 years ago)
• Topics: aeson
• Language: Haskell
• Homepage:
• Size: 19.5 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

Awesome Lists containing this project

README

          
# aeson-possible

[![Build & Test](https://github.com/jonathanjouty/aeson-possible/actions/workflows/ci-haskell.yml/badge.svg)](https://github.com/jonathanjouty/aeson-possible/actions/workflows/ci-haskell.yml)

Three-valued possible types for use with `aeson`.

Useful for use in PATCH endpoints: use in records which have `ToJSON` and

`FromJSON` instances.

Inspired by the [`possible`](https://hackage.haskell.org/package/possible)

package, but additionally provides To/FromJSON instances using `aeson >= 2.2`'s

`omitField` and `omittedField` machinery.

## Usage

Use `Possible a` in your records

```hs

data MyRecord = MyRecord

    { myBool :: Possible Bool

    , myInt  :: Possible Int

    , myStr  :: Possible Text

    }

    deriving (Generic)

```

and then make sure to use the correct options if you are generically deriving

your To/FromJSON instances:

```hs

instance ToJSON MyRecord where

    toJSON = genericToJSON $ defaultOptions{omitNothingFields = True}

instance FromJSON MyRecord where

    parseJSON = genericParseJSON $ defaultOptions{allowOmittedFields = True}

```

Note that `omitNothingFields` affects `ToJSON`, and `allowOmittedFields`

affects `FromJSON`. You can, of course, also set both to `True`.

If you are creating instances any other way, see `aeson`'s documentation for

how to make use of `omitField` and `omittedField`.

_Caveat:_ if you are using `Possible` outside a record, even a `Missing` value

will likely be encoded as `null` (_e.g._ if you have a list of `Possible`

values).