Json.Field

The JSON field options and the string escaping both JSON derivers share.

Programs write the options as #[Json.Key …], #[Json.Skip], and #[Json.Default …] through Json, which re-exports FieldOption. The rest of this module serves derivers and decoders that must match what the encoder writes.

FieldOption

type FieldOption    = Key String    | Skip    | Default CodeSource

An option on a record field, read by the JSON derivers. Each may occur once per field, emitted keys must be unique, and options anywhere but on a record field are rejected. Violations fail at compile time, at the attribute.

Constructors

Key

Key : String -> FieldOptionSource

Use this wire key instead of the field name.

Skip

Skip : FieldOptionSource

Omit the field when encoding and ignore it when decoding. It requires Default and cannot combine with Key.

Default

Default : Code -> FieldOptionSource

The value to use when decoding finds no key. The code is checked against the field’s type, keeps the scope it was written in, and runs only when the fallback is needed.

FieldSettings

type FieldSettings =    { key : String    , skip : Bool    , fallback : Maybe Code    , keySite : Maybe Site    , skipSite : Maybe Site    , defaultSite : Maybe Site    }Source

One field’s options, collected and checked.

Fields

key

key : StringSource

The wire key: the field name unless Key renames it.

skip

skip : BoolSource

Whether Skip applies.

fallback

fallback : Maybe CodeSource

The Default code, if any.

keySite

keySite : Maybe SiteSource

Where Key was written, for diagnostics.

skipSite

skipSite : Maybe SiteSource

Where Skip was written.

defaultSite

defaultSite : Maybe SiteSource

Where Default was written.

escapeChar

escapeChar : Char -> StringSource

The JSON escape for a character that cannot appear plainly in a string.

import Char
import Json.Field

Json.Field.escapeChar '"' == "\\\""
Json.Field.escapeChar '\n' == "\\n"
Json.Field.escapeChar (Maybe.withDefault 'x' (Char.fromCode 1)) == "\\u0001"

fieldSettings

fieldSettings : String -> Attributes -> FieldSettingsSource

The settings of the field name with these attributes, failing at compile time on a repeated option or an invalid combination.

plainChar

plainChar : Char -> BoolSource

Whether a character appears unescaped in a JSON string.

quote

quote : String -> StringSource

A JSON string literal, quotes included.

import Json.Field

Json.Field.quote "a\"b" == "\"a\\\"b\""

validateJSONSchema

validateJSONSchema : TypeInfo -> ()Source

Checks every JSON option on a type: unique keys among emitted record fields, and no options anywhere but on record fields.