open Reified
open Reified.Refinements
open Reified.Result
open Reified.Schema.Json

What Data represents

Data represents structured values with six cases. The model maps directly to JSON and also works for fixtures, configuration, command-line input, form values, events, and other tree-shaped data.

type Data =
    | Null
    | Text of string
    | Number of token: string
    | Bool of bool
    | List of Data list
    | Object of (string * Data) list

Data.Null

Null is a present value with no scalar content. In JSON it renders as null.

Data.render Data.Null
// => "null"

A null field is different from an absent field. In literal syntax, "value" => nil includes a null field, while "value" ?=> None omits the field.

Data.Text

Text stores a .NET string and renders it as a JSON string with the required escaping.

Data.render (Data.Text "Ada\nLovelace")
// => "\"Ada\\nLovelace\""

A null .NET string converts to Data.Null; it does not become Data.Text null.

Data.Number

Number stores the number as a token rather than converting every number to one CLR numeric type. This retains large integers, decimal precision, trailing zeros, and exponent notation.

Data.Number "1.2300e+4"

The token is visible to exact comparison: 1, 1.0, and 1e0 are different. Use the num function rather than the union case when accepting text, because num checks that the token is a valid JSON number.

See Numbers for conversion rules and examples.

Data.Bool

Bool stores true or false and renders it without quotes.

Data.render (Data.Bool true)
// => "true"

Data.List

List stores ordered Data values. Order and repeated values are preserved.

Data.render (Data.List [ Data.Text "author"; Data.Text "admin" ])
// => "[\"author\", \"admin\"]"

Exact comparison checks every item and its position. Matching can instead check an ordered subsequence, an unordered subset, every item, or at least one item.

Data.Object

Object stores an ordered list of name/value pairs. It preserves declaration order and duplicate field names.

let value =
    Data.Object [
        "name", Data.Text "Ada"
        "name", Data.Text "Grace"
    ]

Data.render value
// => "{ name: \"Ada\", name: \"Grace\" }"

Path lookup and edits select the last field when a name is repeated. Exact comparison observes every field, including duplicates and order. Partial object matching consumes matching duplicate fields one occurrence at a time.

Paths

DataPath identifies nested fields and zero-based list indexes. String paths use dots for ordinary field names, brackets for indexes, and quoted brackets for names containing punctuation.

DataPath.parse "customer.roles[1]"
// => [ DataPathSegment.Name "customer"; DataPathSegment.Name "roles"; DataPathSegment.Index 1 ]

DataPath.parse "metadata[\"build.version\"]"
// => [ DataPathSegment.Name "metadata"; DataPathSegment.Name "build.version" ]

The empty path "" addresses the root value.