@metaobjectsdev/metadata

The metamodel loader, typed views, and constants for the MetaObjects standard. This is the foundation package every other @metaobjectsdev/* package builds on — it parses metaobjects/*.json files into a typed object model, resolves extends and overlay merging, and exposes the 11-type vocabulary as named constants.

Install

pnpm add @metaobjectsdev/metadata

Usage

import { MetaDataLoader, InMemoryStringSource } from "@metaobjectsdev/metadata";

const json = `{ "metadata.root": { "package": "demo", "children": [] } }`;
const result = await new MetaDataLoader().load([new InMemoryStringSource(json)]);

The public loader API is MetaDataLoader + InMemoryStringSource. A MetaDataLoader instance is single-use; construct a new one per load.

Loader errors (FR5a)

Every loader error conforms to the cross-port LoaderError envelope (ADR-0009):

interface LoaderError {
  code: string;            // ERR_UNKNOWN_TYPE, ERR_BAD_ATTR_VALUE, ...
  message: string;
  source: ErrorSource;     // always populated
}

type ErrorSource =
  | { format: "json"; files: [string]; jsonPath: string }
  | { format: "yaml"; files: [string]; jsonPath: string; yamlPosition?: { line: number; col: number } }
  | { format: "merged"; files: string[]; jsonPath: string; contributors: Contributor[] }
  | { format: "resolved"; files: string[]; jsonPath?: string; referrer?: string; target?: string }
  | { format: "database"; dbLocation: { table: string; id: string }; jsonPath?: string }
  | { format: "code"; caller?: string };

Every MetaData node also carries a populated source field, so post-load consumers (drift detection, MCP, debug tools) can answer "where did this node come from?" without an extra lookup table.

LoadResult.warnings is a parallel LoaderWarning[] channel — same envelope shape, WARN_* prefixed codes. Pre-FR5a string warnings are wrapped at the loader boundary as WARN_LEGACY envelopes; FR5c will retire the legacy code by routing each emit site through a proper envelope-shaped helper.

The package re-exports the envelope types and the codeSource() helper for consumers that catch + repackage ParseErrors or build synthetic envelopes for programmatic-construction tests:

import type {
  ErrorSource,
  LoaderError,
  LoaderWarning,
  NodeContext,
  Contributor,
} from "@metaobjectsdev/metadata";
import { codeSource } from "@metaobjectsdev/metadata";

See ADR-0009 for the full schema and the FR5 family for the per-error-class rollout plan (5a JSON shape, 5b YAML positions, 5c multi-file merge attribution, 5d reference resolution, 5e database sources).

Links

• Spec
• Metamodel reference

License

Apache 2.0 — see LICENSE at the repo root.