feature: add federation-link-util library

packages/libraries/federation-link-utils/README.md

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+# GraphQL Hive - federation-link-utils
+
+[Hive](https://the-guild.dev/graphql/hive) is a fully open-source schema registry, analytics,
+metrics and gateway for [GraphQL federation](https://the-guild.dev/graphql/hive/federation) and
+other GraphQL APIs.
+
+---
+
+This library can be used to make a custom features for GraphQL schemas backed by Federation's
+[`@link`](https://www.apollographql.com/docs/graphos/reference/federation/directives#the-link-directive)
+directive.
+
+## Features
+
+- Link version support.
+- Import `as`/namespacing support that follows the [link spec](https://specs.apollo.dev/link/v1.0/).
+- Only `graphql` as a dependency.
+
+## Usage
+
+This library is for power users who want to develop their own Federation 2 `@link` feature(s). It
+enables you to define and support multiple versions of the feature and to easily reference the named
+imports. This includes official federation features if you choose to implement them yourself.
+
+```graphql
+# schema.graphql
+
+directive @example(eg: String!) on FIELD
+extend schema @link(url: "https://specs.graphql-hive.com/example/v0.1", import: ["@example"])
+type Query {
+  user: User @example(eg: "query { user { id name } }")
+}
+
+type User {
+  id: ID!
+  name: String
+}
+```
+
+```typescript
+// specs.ts
+import {
+  detectLinkedImplementations,
+  FEDERATION_V1,
+  LinkableSpec
+} from '@graphql-hive/federation-link-utils'
+
+const exampleSpec = new LinkableSpec('https://specs.graphql-hive.com/example', {
+  [FEDERATION_V1]: resolveImportName => (typeDefs: DocumentNode) => {
+    // option to support federation 1 schemas. Be extremely cautious here because versioning
+    // cannot be done safely.
+  },
+  'v0.1': resolveImportName => (typeDefs: DocumentNode) => {
+    const examples: Record<string, string> = {}
+    const exampleName = resolveImportName('@example')
+    visit(typeDefs, {
+      FieldDefinition: node => {
+        const example = node.directives?.find(d => d.name.value === exampleName)
+        if (example) {
+          examples[node.name.value] = (
+            example.arguments?.find(a => a.name.value === 'eg')?.value as
+              | StringValueNode
+              | undefined
+          )?.value
+        }
+      }
+    })
+    return examples
+  }
+})
+const typeDefs = parse(sdl)
+const linkedSpecs = detectLinkedImplementations(typeDefs, [exampleSpec])
+const result = linkedSpecs.map(apply => apply(typeDefs))
+
+// result[0] ==> { user: "query { user { id name } }"}
+```
+
+The LinkableSpec is unopinionated on how the spec is implemented. However, it's recommended to keep
+this consistent between all LinkedSpecs. I.e. always return a yoga plugin.

packages/libraries/federation-link-utils/package.json

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+{
+  "name": "@graphql-hive/federation-link-utils",
+  "version": "0.0.1",
+  "type": "module",
+  "repository": {
+    "type": "git",
+    "url": "graphql-hive/platform",
+    "directory": "packages/libraries/federation-link-utils"
+  },
+  "homepage": "https://the-guild.dev/graphql/hive",
+  "author": {
+    "email": "[email protected]",
+    "name": "The Guild",
+    "url": "https://the-guild.dev"
+  },
+  "license": "MIT",
+  "private": true,
+  "engines": {
+    "node": ">=16.0.0"
+  },
+  "main": "dist/cjs/index.js",
+  "module": "dist/esm/index.js",
+  "exports": {
+    ".": {
+      "require": {
+        "types": "./dist/typings/index.d.cts",
+        "default": "./dist/cjs/index.js"
+      },
+      "import": {
+        "types": "./dist/typings/index.d.ts",
+        "default": "./dist/esm/index.js"
+      },
+      "default": {
+        "types": "./dist/typings/index.d.ts",
+        "default": "./dist/esm/index.js"
+      }
+    },
+    "./package.json": "./package.json"
+  },
+  "typings": "dist/typings/index.d.ts",
+  "scripts": {
+    "build": "node ../../../scripts/generate-version.mjs && bob build",
+    "check:build": "bob check"
+  },
+  "peerDependencies": {
+    "graphql": "^0.13.0 || ^14.0.0 || ^15.0.0 || ^16.0.0"
+  },
+  "devDependencies": {
+    "graphql": "16.9.0",
+    "tslib": "2.8.1",
+    "vitest": "2.0.5"
+  },
+  "publishConfig": {
+    "registry": "https://registry.npmjs.org",
+    "access": "public",
+    "directory": "dist"
+  },
+  "sideEffects": false,
+  "typescript": {
+    "definition": "dist/typings/index.d.ts"
+  }
+}

packages/libraries/federation-link-utils/src/__tests__/index.spec.ts

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+import { DocumentNode, parse, StringValueNode, visit } from 'graphql';
+import { detectLinkedImplementations, FEDERATION_V1, LinkableSpec } from '../index';
+
+const metaSpec = new LinkableSpec('https://specs.graphql-hive.com/metadata', {
+  [FEDERATION_V1]: _resolveImportName => (_typeDefs: DocumentNode) => {
+    return 'Missing federation 2 support';
+  },
+
+  // The return value could be used to map sdl, collect information, or create a graphql yoga plugin.
+  // In this test, it's used to collect metadata information from the schema.
+  'v0.1': resolveImportName => (typeDefs: DocumentNode) => {
+    const collectedMeta: Record<string, Record<string, string>> = {};
+    const metaName = resolveImportName('@meta');
+    const exampleName = resolveImportName('@example');
+    visit(typeDefs, {
+      FieldDefinition: node => {
+        let metaData: Record<string, string> = {};
+        const fieldName = node.name.value;
+        const meta = node.directives?.find(d => d.name.value === metaName);
+        if (meta) {
+          metaData['name'] =
+            (
+              meta.arguments?.find(a => a.name.value === 'name')?.value as
+                | StringValueNode
+                | undefined
+            )?.value ?? '??';
+          metaData['content'] =
+            (
+              meta.arguments?.find(a => a.name.value === 'content')?.value as
+                | StringValueNode
+                | undefined
+            )?.value ?? '??';
+        }
+
+        const example = node.directives?.find(d => d.name.value === exampleName);
+        if (example) {
+          metaData['eg'] =
+            (
+              example.arguments?.find(a => a.name.value === 'eg')?.value as
+                | StringValueNode
+                | undefined
+            )?.value ?? '??';
+        }
+        if (Object.keys(metaData).length) {
+          collectedMeta[fieldName] ??= {};
+          collectedMeta[fieldName] = Object.assign(collectedMeta[fieldName], metaData);
+        }
+        return;
+      },
+    });
+    // collect metadata
+    return `running on v0.1.\nFound metadata: ${JSON.stringify(collectedMeta)}}`;
+  },
+  'v0.2': _resolveImportName => (_typeDefs: DocumentNode) => {
+    // collect metadata
+    return `running on v0.2...`;
+  },
+});
+
+test('LinkableSpec and detectLinkedImplementations can be used to apply linked schema in Federation 2.x', () => {
+  const sdl = `
+    directive @meta(name: String!, content: String!) on SCHEMA | FIELD
+    directive @metadata__example(eg: String!) on FIELD
+    extend schema
+      @link(url: "https://specs.apollo.dev/federation/v2.3")
+      @link(url: "https://specs.graphql-hive.com/metadata/v0.1", import: ["@meta"])
+
+    type Query {
+      ping: String @meta(name: "owner", content: "hive-console-team")
+      pong: String @metadata__example(eg: "1...2...3... Pong")
+    }
+  `;
+  const typeDefs = parse(sdl);
+  const linked = detectLinkedImplementations(typeDefs, [metaSpec]);
+  expect(linked.map(link => link(typeDefs))).toMatchInlineSnapshot(`
+    [
+      running on v0.1.
+    Found metadata: {"ping":{"name":"owner","content":"hive-console-team"},"pong":{"eg":"1...2...3... Pong"}}},
+    ]
+  `);
+});
+
+test('LinkableSpec and detectLinkedImplementations can be used to apply linked schema in schemas that are missing the link directive', () => {
+  const sdl = `
+    directive @meta(name: String!, content: String!) on SCHEMA | FIELD
+
+    type Query {
+      ping: String @meta(name: "owner", content: "hive-console-team")
+    }
+  `;
+  const typeDefs = parse(sdl);
+  const linked = detectLinkedImplementations(typeDefs, [metaSpec]);
+  expect(linked.map(link => link(typeDefs))).toMatchInlineSnapshot(`
+    [
+      Missing federation 2 support,
+    ]
+  `);
+});

packages/libraries/federation-link-utils/src/__tests__/link-url.spec.ts

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+import { FederatedLinkUrl } from '../link-url';
+
+describe('FederatedLinkUrl', () => {
+  test.each([
+    [
+      'https://spec.example.com/a/b/mySchema/v1.0/',
+      'https://spec.example.com/a/b/mySchema',
+      'mySchema',
+      'v1.0',
+    ],
+    ['https://spec.example.com', 'https://spec.example.com', null, null],
+    [
+      'https://spec.example.com/mySchema/v0.1?q=v#frag',
+      'https://spec.example.com/mySchema',
+      'mySchema',
+      'v0.1',
+    ],
+    ['https://spec.example.com/v1.0', 'https://spec.example.com', null, 'v1.0'],
+    ['https://spec.example.com/vX', 'https://spec.example.com/vX', 'vX', null],
+  ])('fromUrl correctly parses the identity, name, and version', (url, identity, name, version) => {
+    const spec = FederatedLinkUrl.fromUrl(url);
+    expect(spec.identity).toBe(identity);
+    expect(spec.name).toBe(name);
+    expect(spec.version).toBe(version);
+  });
+
+  test.each([
+    ['https://spec.example.com/a/b/mySchema/v1.2/', 'https://spec.example.com/a/b/mySchema/v1.0/'],
+    ['https://spec.example.com', 'https://spec.example.com'],
+    ['https://spec.example.com/mySchema/v0.1?q=v#frag', 'https://spec.example.com/mySchema/v0.1'],
+    ['https://spec.example.com/v1.100', 'https://spec.example.com/v1.0'],
+    ['https://spec.example.com/vX', 'https://spec.example.com/vX'],
+  ])(
+    'supports returns true for specs with the same identity and compatible versions',
+    (url0, url1) => {
+      expect(FederatedLinkUrl.fromUrl(url0).supports(FederatedLinkUrl.fromUrl(url1))).toBe(true);
+    },
+  );
+
+  test.each([
+    ['https://spec.example.com/a/b/mySchema/v1.0/', 'https://spec.example.com/a/b/mySchema/v1.2/'],
+    ['https://spec.example.com/mySchema/v0.1?q=v#frag', 'https://spec.example.com/mySchema/v0.2'],
+    ['https://spec.example.com/v1.0', 'https://spec.example.com/v1.100'],
+  ])(
+    'supports returns false for specs with the same identity and incompatible versions',
+    (url0, url1) => {
+      expect(FederatedLinkUrl.fromUrl(url0).supports(FederatedLinkUrl.fromUrl(url1))).toBe(false);
+    },
+  );
+
+  test.each([
+    ['https://spec.example.com/a/b/mySchema/v1.0/', 'https://spec.example.com/a/b/mySchema/v1.0'],
+    ['https://spec.example.com', 'https://spec.example.com'],
+    ['https://spec.example.com/mySchema/v0.1?q=v#frag', 'https://spec.example.com/mySchema/v0.1'],
+    ['https://spec.example.com/v1.0', 'https://spec.example.com/v1.0'],
+    ['https://spec.example.com/vX', 'https://spec.example.com/vX'],
+  ])('toString returns the normalized url', (url, str) => {
+    expect(FederatedLinkUrl.fromUrl(url).toString()).toBe(str);
+  });
+});

packages/libraries/federation-link-utils/src/__tests__/link.spec.ts

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+import { parse } from 'graphql';
+import { FederatedLink } from '../link';
+
+function trimMultiline(str: string): string {
+  return str
+    .split('\n')
+    .map(s => s.trim())
+    .filter(l => !!l)
+    .join('\n');
+}
+
+describe('FederatedLink', () => {
+  test.each([
+    `
+      extend schema
+        @link(url: "https://specs.apollo.dev/link/v1.0")
+        @link(url: "https://specs.apollo.dev/federation/v2.0")
+    `,
+    `
+      extend schema
+        @link(url: "https://specs.apollo.dev/link/v1.0", as: "@linkz")
+        @link(url: "https://specs.apollo.dev/federation/v2.0", as: "fed", import: ["@key"])
+    `,
+    `
+      extend schema
+        @link(url: "https://specs.apollo.dev/link/v1.0")
+        @link(url: "https://specs.apollo.dev/federation/v2.0", import: [{ name: "@key", as: "@lookup" }])
+    `,
+  ])('fromTypedefs', (sdl: string) => {
+    // string manipulate to extract just the link trings
+    const firstLinkPos = sdl.indexOf('@link(');
+    const linksOnly = trimMultiline(sdl.substring(firstLinkPos));
+    // compare to parsed result
+    const typeDefs = parse(sdl);
+    const links = FederatedLink.fromTypedefs(typeDefs);
+    expect(links.join('\n')).toBe(linksOnly);
+  });
+
+  test('resolveImportName', () => {
+    const sdl = `
+      extend schema
+        @link(url: "https://specs.apollo.dev/link/v1.0")
+        @link(url: "https://specs.apollo.dev/federation/v2.0", import: [{ name: "@key", as: "@lookup" }, "@provides"])
+        @link(url: "https://unnamed.graphql-hive.com/v0.1", import: ["@meta"])
+        @link(url: "https://specs.graphql-hive.com/hive/v0.1", import: ["@group"], as: "hivelink")
+    `;
+    const links = FederatedLink.fromTypedefs(parse(sdl));
+    const federationLink = links.find(l => l.identity === 'https://specs.apollo.dev/federation');
+    expect(federationLink).toBeDefined();
+    // aliased
+    expect(federationLink?.resolveImportName('@key')).toBe('lookup');
+    // unimported
+    expect(federationLink?.resolveImportName('@external')).toBe('federation__external');
+    // imported by name only
+    expect(federationLink?.resolveImportName('@provides')).toBe('provides');
+
+    // default import
+    const linkLink = links.find(l => l.identity === 'https://specs.apollo.dev/link');
+    expect(linkLink?.resolveImportName('@link')).toBe('link');
+
+    // unnamespaced
+    const unnamedLink = links.find(l => l.identity === 'https://unnamed.graphql-hive.com');
+    expect(unnamedLink).toBeDefined();
+    expect(unnamedLink?.resolveImportName('@meta')).toBe('meta');
+    expect(unnamedLink?.resolveImportName('@unmentioned')).toBe('unmentioned');
+
+    // imported as
+    const hiveLink = links.find(l => l.identity === 'https://specs.graphql-hive.com/hive');
+    expect(hiveLink?.resolveImportName('@group')).toBe('group');
+    expect(hiveLink?.resolveImportName('@eg')).toBe('hivelink__eg');
+  });
+});

packages/libraries/federation-link-utils/src/__tests__/linkable-spec.spec.ts

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+import { parse } from 'graphql';
+import { FederatedLink } from '../link';
+import { LinkableSpec } from '../linkable-spec';
+
+describe('LinkableSpec', () => {
+  test('getSupportingVersion returned the most compatible version.', () => {
+    const spec = new LinkableSpec('https://specs.graphql-hive.com/example', {
+      'v2.0': _resolveImportName => 'Version 2.0 used.',
+      'v1.0': _resolveImportName => 'Version 1.0 used.',
+    });
+    const sdl = `
+      extend schema
+        @link(url: "https://specs.graphql-hive.com/example/v1.1")
+    `;
+
+    const links = FederatedLink.fromTypedefs(parse(sdl));
+    const specImpl = spec.detectImplementation(links);
+    expect(specImpl).toBe('Version 1.0 used.');
+  });
+});