JSON and selections

Any view also loads as serde_json::Value objects, whole or a selection of its fields. A selection is written like a GraphQL selection set; only its columns are selected and only its child queries run (MPA-JSON-3).

use mabat::Selection;

let selection = Selection::parse("name assignee { name } children { name }")?;
let tasks = mabat::load::<TaskView>().select(selection).json(&mut conn).await?;
// [{ "name": "Release", "assignee": { "name": "Ada" }, "children": [{ "name": "Write docs" }] }]

The JSON

• Columns use their Rust type’s Serialize; a type without it fails only when loaded as JSON (MPA-JSON-1, MPA-JSON-2).
• #[view(json)] columns are written as the JSON they hold.
• Collections are arrays, maps are objects, references are objects or null.
• Enums are objects whose __typename names the variant; tuple fields are _0, _1, …

Selections

• A collection or reference selected by name alone loads its view’s columns and embedded values, not its own collections or references, so every selection has a finite depth (MPA-JSON-4).
• Recursive and graph views load as trees as deep as the selection asks (MPA-JSON-5).
• Overrides apply to selections; typed terminals refuse them (MPA-JSON-6).
• Selections combine with filters, paging and nested arguments.