`federation` — multi-plugin SDL merger

(no submodules)

Purpose

federation is the engine's facade over the canonical mergeSdl function from @suaveplan/api-graphql. Apollo doesn't see federated plugin contributions directly — the engine collects every plugin's SDL via the abstract GraphqlRegistry, federates them through this module, and feeds the merged SDL to buildSchema(). Collision detection, namespace wrapping, and strict-mode policy come for free because all three are owned by the abstract merger.

The module is intentionally a one-line passthrough; it exists so the package surface signals "yes, Apollo federates the same way Yoga does — GRAPHQL.SCHEMA_COLLISION is the canonical code on either engine".

Features

1:1 delegation to @suaveplan/api-graphql.mergeSdl — no shape change, no behaviour change.
Same collision semantics as Yoga — GRAPHQL.SCHEMA_COLLISION is raised, NOT a GRAPHQL_APOLLO.* code.
Strict-mode propagation — strictNamespace: true requires every plugin to declare a graphql.namespace.
Returns the canonical MergedSchema shape so engine internals stay assignable to the abstract contract.

Usage: Basic

import { federateForApollo } from "@suaveplan/api-graphql-apollo/federation";

const merged = federateForApollo([
    { plugin: "billing", typeDefs: ["type Query { invoice: String! }"] },
    { plugin: "users", typeDefs: ["extend type Query { me: String! }"] },
]);
console.log(merged.sdl);

Usage: Advanced

Enable strict-mode federation across all plugins to enforce a namespace contract before the host even compiles:

import { federateForApollo } from "@suaveplan/api-graphql-apollo/federation";

federateForApollo(contributions, { strictNamespace: true });
// → throws GRAPHQL.NAMESPACE_REQUIRED if any plugin omitted namespace

API Reference

federateForApollo(contributions, options?): MergedSchema
- delegates to @suaveplan/api-graphql.mergeSdl.

Implementation Notes

The function exists primarily so the package's TypeScript exports expose a federateForApollo symbol that mirrors the sibling federateForYoga (when the Yoga adapter lands). The behavioural contract is owned by the abstract mergeSdl. Tests verify that GRAPHQL.SCHEMA_COLLISION and GRAPHQL.NAMESPACE_REQUIRED are raised through this wrapper — concrete proof that Apollo and Yoga agree on the federation contract.

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federation — multi-plugin SDL merger