autodocodec/README.md
2021-11-17 14:39:36 +01:00

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# Autodocodec
Autodocodec is short for "self(auto)- documenting encoder and decoder".
In short:
You write a single instance, of the 'Codec' type-class, for your type, and you get:
* [A 'ToJSON' instance from 'aeson' with both a `toJSON` and `toEncoding` implementation](https://hackage.haskell.org/package/aeson-2.0.1.0/docs/Data-Aeson-Types.html#t:ToJSON)
* [A 'FromJSON' instance from 'aeson'](https://hackage.haskell.org/package/aeson-2.0.1.0/docs/Data-Aeson-Types.html#t:FromJSON)
* [A 'ToYaml` instance from 'yaml'](https://hackage.haskell.org/package/yaml-0.11.7.0/docs/Data-Yaml-Builder.html#t:ToYaml)
* [A json schema](http://json-schema.org/)
* [A nicely-coloured human-readable yaml schema](./autodocodec-yaml)
* [A Swagger schema](https://swagger.io/specification/v2/)
* [An Openapi schema](https://swagger.io/specification/)
See [the golden test directory](./autodocodec-api-usage/test_resources) directory for example outputs.
## Features
* ✓ Correct-by-construction encoding and decoding, without generating code.
* ✓ Generate automatically-correct documentation from code.
* ✓ Support for recursive types.
## State of this project
This project is ready to try out!
## Fully featured example
``` haskell
data Example = Example
{ exampleTextField :: !Text,
exampleIntField :: !Int
}
deriving stock (Show, Eq, Generic)
deriving
( FromJSON, -- <- FromJSON instance for free.
ToJSON, -- <- ToJSON instance for free.
Swagger.ToSchema, -- <- Swagger schema for free.
OpenAPI.ToSchema -- <- OpenAPI schema for free.
)
via (Autodocodec Example)
instance HasCodec Example where
codec =
object "Example" $
Example
<$> requiredField "text" "documentation for the text field" .= exampleTextField
<*> requiredField "int" "documentation for the int field" .= exampleIntField
```
## Tests
While we don't provide any actual guarantees, we do have tests for the following properties that we would like to maintain:
* [Encoding and decoding roundtrips through JSON.](./autodocodec-api-usage/test/Autodocodec/AesonSpec.hs)
* [For standard types, encoding behaves in the same way that `aeson` does.](./autodocodec-api-usage/test/Autodocodec/AesonSpec.hs)
* [Error messages for decoding are still good.](./autodocodec-api-usage/test/Autodocodec/AesonSpec.hs)
* [Generated Human-readible documentation looks good.](./autodocodec-api-usage/test/Autodocodec/Yaml/DocumentSpec.hs)
* [Generated JSON schemas look good.](./autodocodec-api-usage/test/Autodocodec/Aeson/SchemaSpec.hs)
* [Generated Swagger schemas look good.](./autodocodec-api-usage/test/Autodocodec/SwaggerSpec.hs)
* [Generated OpenAPI schemas look good.](./autodocodec-api-usage/test/Autodocodec/OpenAPISpec.hs)
* [Generated values are accepted by the corresponding generated JSON schemas.](./autodocodec-api-usage/test/Autodocodec/Aeson/SchemaSpec.hs)
* [Generated values are accepted by the corresponding generated Swagger schemas.](./autodocodec-api-usage/test/Autodocodec/SwaggerSpec.hs)
* [Generated values are accepted by the corresponding generated OpenAPI schemas.](./autodocodec-api-usage/test/Autodocodec/OpenAPISpec.hs)
* [Encoding and decoding roundtrips through YAML.](./autodocodec-api-usage/test/Autodocodec/YamlSpec.hs)
* [We try to make sure that backward compatibility is maintained.](./autodocodec-api-usage/src/Autodocodec/Usage.hs)
* [Codecs are more or less inspectable.](./autodocodec-api-usage/test/Autodocodec/ShowSpec.hs)
* [Encoding and decoding is still fast](./autodocodec-api-usage/bench/Main.hs)