created a new precomposition rule to detect fed2 schemas

federation-js/CHANGELOG.md

@@ -6,7 +6,7 @@ This CHANGELOG pertains only to Apollo Federation packages in the `0.x` range. T
 
 > The changes noted within this `vNEXT` section have not been released yet.  New PRs and commits which introduce changes should include an entry in this `vNEXT` section as part of their development.  When a release is being prepared, a new header will be (manually) created below and the appropriate changes within that release will be moved into the new section.
 
-- _Nothing yet! Stay tuned._
+- Composition will detect and error if it finds fed2 subgraphs [PR #1723](https://github.com/apollographql/federation/pull/1723).
 
 ## v0.36.0
 - Support for Node 17 [PR #1648](https://github.com/apollographql/federation/pull/1648).

federation-js/src/composition/validate/preComposition/__tests__/noFed2Subgraphs.test.ts

@@ -0,0 +1,105 @@
+import { noFed2Subgraphs as validateNoFed2Subgraphs } from '../';
+import {
+  gql,
+  graphqlErrorSerializer,
+} from 'apollo-federation-integration-testsuite';
+
+expect.addSnapshotSerializer(graphqlErrorSerializer);
+
+describe('noFed2Subgraphs', () => {
+  it('does not compose when fed2 semantics are detected. fed2.0', () => {
+    const serviceA = {
+      typeDefs: gql`
+        extend schema
+          @link(
+            url: "https://specs.apollo.dev/federation/v2.0",
+            import: [ "@key" ]
+          )
+        type Product @key(fields: "color { id value }") {
+          sku: String!
+          upc: String!
+          color: Color!
+        }
+
+        type Color {
+          id: ID!
+          value: String!
+        }
+      `,
+      name: 'serviceA',
+    };
+
+    const errors = validateNoFed2Subgraphs(serviceA);
+    expect(errors).toMatchInlineSnapshot(`
+      Array [
+        Object {
+          "code": "NO_FED2_SUBGRAPHS",
+          "locations": Array [],
+          "message": "[serviceA] Schema contains a Federation 2 subgraph. Only federation 1 subgraphs can be composed with the fed1 composer.",
+        },
+      ]
+    `);
+  });
+
+  it('does not compose when fed2 semantics are detected. link 1.0', () => {
+    const serviceA = {
+      typeDefs: gql`
+        extend schema
+          @link(
+            url: "https://specs.apollo.dev/link/v1.0"
+          )
+        type Product @key(fields: "color { id value }") {
+          sku: String!
+          upc: String!
+          color: Color!
+        }
+
+        type Color {
+          id: ID!
+          value: String!
+        }
+      `,
+      name: 'serviceA',
+    };
+
+    const errors = validateNoFed2Subgraphs(serviceA);
+    expect(errors).toMatchInlineSnapshot(`
+      Array [
+        Object {
+          "code": "NO_FED2_SUBGRAPHS",
+          "locations": Array [],
+          "message": "[serviceA] Schema contains a Federation 2 subgraph. Only federation 1 subgraphs can be composed with the fed1 composer.",
+        },
+      ]
+    `);
+  });
+
+
+  it('composes just fine when versions are sufficiently old', () => {
+    const serviceA = {
+      typeDefs: gql`
+        extend schema
+          @link(
+            url: "https://specs.apollo.dev/link/v0.2"
+          )
+          @link(
+            url: "https://specs.apollo.dev/federation/v1.0"
+          )
+        type Product @key(fields: "color { id value }") {
+          sku: String!
+          upc: String!
+          color: Color!
+        }
+
+        type Color {
+          id: ID!
+          value: String!
+        }
+      `,
+      name: 'serviceA',
+    };
+
+    const errors = validateNoFed2Subgraphs(serviceA);
+    expect(errors).toEqual([]);
+  });
+});

federation-js/src/composition/validate/preComposition/index.ts

@@ -4,3 +4,4 @@ export { keyFieldsMissingExternal } from './keyFieldsMissingExternal';
 export { reservedFieldUsed } from './reservedFieldUsed';
 export { duplicateEnumOrScalar } from './duplicateEnumOrScalar';
 export { duplicateEnumValue } from './duplicateEnumValue';
+export { noFed2Subgraphs } from './noFed2Subgraphs';

federation-js/src/composition/validate/preComposition/noFed2Subgraphs.ts

@@ -0,0 +1,50 @@
+import { visit, GraphQLError, Kind } from 'graphql';
+import { ServiceDefinition } from '../../types';
+
+import { errorWithCode, findDirectivesOnNode } from '../../utils';
+
+/**
+ * - There are no subgraphs that @link to a version that is unsupported by 1.0 composition.
+ */
+export const noFed2Subgraphs = ({
+  name: serviceName,
+  typeDefs,
+}: ServiceDefinition) => {
+  const errors: GraphQLError[] = [];
+  visit(typeDefs, {
+    SchemaExtension(schemaExtensionNode) {
+      const directives = findDirectivesOnNode(schemaExtensionNode, 'link').filter(directive => {
+        if (directive.name.value === 'link') {
+          const argNode = directive.arguments?.find(
+            arg => arg.name.value === 'url',
+          );
+          if (argNode) {
+            if (argNode.value.kind === Kind.STRING) {
+              const url = argNode.value.value;
+              const [,spec, versionRaw] = url.match(
+                /(federation|link)\/v(\d*\.\d*)/,
+              )!;
+
+              const version = parseFloat(versionRaw);
+              return (
+                (spec === 'federation' && version >= 2.0) ||
+                (spec === 'link' && version >= 1.0)
+              );
+            }
+          }
+        }
+        return false;
+      });
+      if (directives.length > 0) {
+        errors.push(
+          errorWithCode(
+            'NO_FED2_SUBGRAPHS',
+            `[${serviceName}] Schema contains a Federation 2 subgraph. Only federation 1 subgraphs can be composed with the fed1 composer.`,
+          )
+        );
+      }
+    },
+  });
+
+  return errors;
+};