refactor: Introduce "cache-control" plugin and switch req. pipeline t…

…o it.

Similar to 6009d8a, which migrated the tracing package to the plugin
API, this commit introduces a `plugin` (named) export from the
`apollo-cache-control` module.  It similarly accomplishes that by
duplicating the behavior of the `CacheControlExtension` which leveraged the
soon-to-be-deprecated `graphql-extensions`.  The functionality, again, is
intended to be identical in spirit.

Since the delta of the commits was otherwise even _more_ confusing, I've
left the `CacheControlExtension` present and exported and will remove it in a
subsequent commit.

Briefly summarizing what the necessary changes were:

1. We no longer use a class instance to house the extension, which was
   necessitated by the `graphql-extensions` API.  This means that uses of
   `this` have been replaced with function scoped variables by the same name.
2. The logic which actually does the formatting (previously handled by the
   `format` method in `graphql-extension`, now takes place within the plugin
   API's `willSendResponse` method.
3. Rather than leaning on plugin-specific behavior from within the request
   pipeline, the `apollo-cache-control` plugin now makes a number of
   assertions throughout its various life-cycle methods to ensure that the
   `overallCachePolicy` is calculated.
4. Switch tests to use the new `pluginTestHarness` method for testing
   plugins which was introduced in eec87a6 (#3990).

packages/apollo-cache-control/package.json

@@ -12,7 +12,8 @@
   },
   "dependencies": {
     "apollo-server-env": "file:../apollo-server-env",
-    "graphql-extensions": "file:../graphql-extensions"
+    "graphql-extensions": "file:../graphql-extensions",
+    "apollo-server-plugin-base": "file:../apollo-server-plugin-base"
   },
   "peerDependencies": {
     "graphql": "^0.12.0 || ^0.13.0 || ^14.0.0 || ^15.0.0"

packages/apollo-cache-control/src/__tests__/cacheControlExtension.test.ts

@@ -1,59 +1,110 @@
 import { ResponsePath, GraphQLError } from 'graphql';
 import { GraphQLResponse } from 'graphql-extensions';
 import { Headers } from 'apollo-server-env';
-import { CacheControlExtension, CacheScope } from '../';
+import {
+  CacheScope,
+  CacheControlExtensionOptions,
+  CacheHint,
+  __testing__,
+  plugin,
+} from '../';
+const { addHint, computeOverallCachePolicy } = __testing__;
+import {
+  GraphQLRequestContextWillSendResponse,
+} from 'apollo-server-plugin-base';
+import pluginTestHarness from 'apollo-server-core/dist/utils/pluginTestHarness';
 
 describe('CacheControlExtension', () => {
-  let cacheControlExtension: CacheControlExtension;
-
-  beforeEach(() => {
-    cacheControlExtension = new CacheControlExtension();
-  });
-
   describe('willSendResponse', () => {
-    let graphqlResponse: GraphQLResponse;
+    function makePluginWithOptions({
+      pluginInitializationOptions,
+      overallCachePolicy,
+      errors = false,
+    }: {
+      pluginInitializationOptions?: CacheControlExtensionOptions;
+      overallCachePolicy?: Required<CacheHint>;
+      errors?: boolean;
+    } = Object.create(null)) {
+      const pluginInstance = plugin(pluginInitializationOptions);
+
+      return pluginTestHarness({
+        pluginInstance,
+        overallCachePolicy,
+        graphqlRequest: { query: 'does not matter' },
+        executor: () => {
+          const response: GraphQLResponse = {
+            http: {
+              headers: new Headers(),
+            },
+            data: { test: 'test' },
+          };
+
+          if (errors) {
+            response.errors = [new GraphQLError('Test Error')];
+          }
+
+          return response;
+        },
+      });
+    }
 
-    beforeEach(() => {
-      cacheControlExtension.options.calculateHttpHeaders = true;
-      cacheControlExtension.computeOverallCachePolicy = () => ({
+    describe('HTTP cache-control header', () => {
+      const overallCachePolicy: Required<CacheHint> = {
         maxAge: 300,
         scope: CacheScope.Public,
-      });
-      graphqlResponse = {
-        http: {
-          headers: new Headers(),
-        },
-        data: { test: 'test' },
       };
-    });
 
-    it('sets cache-control header', () => {
-      cacheControlExtension.willSendResponse &&
-        cacheControlExtension.willSendResponse({ graphqlResponse });
-      expect(graphqlResponse.http!.headers.get('Cache-Control')).toBe(
-        'max-age=300, public',
-      );
-    });
+      it('is set when calculateHttpHeaders is set to true', async () => {
+        const requestContext = await makePluginWithOptions({
+          pluginInitializationOptions: {
+            calculateHttpHeaders: true,
+          },
+          overallCachePolicy,
+        });
+        expect(requestContext.response.http!.headers.get('Cache-Control')).toBe(
+          'max-age=300, public',
+        );
+      });
 
-    const shouldNotSetCacheControlHeader = () => {
-      cacheControlExtension.willSendResponse &&
-        cacheControlExtension.willSendResponse({ graphqlResponse });
-      expect(graphqlResponse.http!.headers.get('Cache-Control')).toBeNull();
-    };
+      const shouldNotSetCacheControlHeader = (
+        requestContext: GraphQLRequestContextWillSendResponse<any>,
+      ) => {
+        expect(
+          requestContext.response.http!.headers.get('Cache-Control'),
+        ).toBeNull();
+      };
 
-    it('does not set cache-control header if calculateHttpHeaders is set to false', () => {
-      cacheControlExtension.options.calculateHttpHeaders = false;
-      shouldNotSetCacheControlHeader();
-    });
+      it('is not set when calculateHttpHeaders is set to false', async () => {
+        const requestContext = await makePluginWithOptions({
+          pluginInitializationOptions: {
+            calculateHttpHeaders: false,
+          },
+          overallCachePolicy,
+        });
+        shouldNotSetCacheControlHeader(requestContext);
+      });
 
-    it('does not set cache-control header if graphqlResponse has errors', () => {
-      graphqlResponse.errors = [new GraphQLError('Test Error')];
-      shouldNotSetCacheControlHeader();
-    });
+      it('is not set if response has errors', async () => {
+        const requestContext = await makePluginWithOptions({
+          pluginInitializationOptions: {
+            calculateHttpHeaders: false,
+          },
+          overallCachePolicy,
+          errors: true,
+        });
+        shouldNotSetCacheControlHeader(requestContext);
+      });
 
-    it('does not set cache-control header if there is no overall cache policy', () => {
-      cacheControlExtension.computeOverallCachePolicy = () => undefined;
-      shouldNotSetCacheControlHeader();
+      it('does not set cache-control header if there is no overall cache policy', async () => {
+        const requestContext = await makePluginWithOptions({
+          pluginInitializationOptions: {
+            calculateHttpHeaders: false,
+          },
+          overallCachePolicy: undefined,
+          errors: true,
+        });
+        shouldNotSetCacheControlHeader(requestContext);
+      });
     });
   });
 
@@ -71,46 +122,49 @@ describe('CacheControlExtension', () => {
       prev: responseSubPath,
     };
 
+    const hints = new Map();
+    afterEach(() => hints.clear());
+
     it('returns undefined without cache hints', () => {
-      const cachePolicy = cacheControlExtension.computeOverallCachePolicy();
+      const cachePolicy = computeOverallCachePolicy(hints);
       expect(cachePolicy).toBeUndefined();
     });
 
     it('returns lowest max age value', () => {
-      cacheControlExtension.addHint(responsePath, { maxAge: 10 });
-      cacheControlExtension.addHint(responseSubPath, { maxAge: 20 });
+      addHint(hints, responsePath, { maxAge: 10 });
+      addHint(hints, responseSubPath, { maxAge: 20 });
 
-      const cachePolicy = cacheControlExtension.computeOverallCachePolicy();
+      const cachePolicy = computeOverallCachePolicy(hints);
       expect(cachePolicy).toHaveProperty('maxAge', 10);
     });
 
     it('returns undefined if any cache hint has a maxAge of 0', () => {
-      cacheControlExtension.addHint(responsePath, { maxAge: 120 });
-      cacheControlExtension.addHint(responseSubPath, { maxAge: 0 });
-      cacheControlExtension.addHint(responseSubSubPath, { maxAge: 20 });
+      addHint(hints, responsePath, { maxAge: 120 });
+      addHint(hints, responseSubPath, { maxAge: 0 });
+      addHint(hints, responseSubSubPath, { maxAge: 20 });
 
-      const cachePolicy = cacheControlExtension.computeOverallCachePolicy();
+      const cachePolicy = computeOverallCachePolicy(hints);
       expect(cachePolicy).toBeUndefined();
     });
 
     it('returns PUBLIC scope by default', () => {
-      cacheControlExtension.addHint(responsePath, { maxAge: 10 });
+      addHint(hints, responsePath, { maxAge: 10 });
 
-      const cachePolicy = cacheControlExtension.computeOverallCachePolicy();
+      const cachePolicy = computeOverallCachePolicy(hints);
       expect(cachePolicy).toHaveProperty('scope', CacheScope.Public);
     });
 
     it('returns PRIVATE scope if any cache hint has PRIVATE scope', () => {
-      cacheControlExtension.addHint(responsePath, {
+      addHint(hints, responsePath, {
         maxAge: 10,
         scope: CacheScope.Public,
       });
-      cacheControlExtension.addHint(responseSubPath, {
+      addHint(hints, responseSubPath, {
         maxAge: 10,
         scope: CacheScope.Private,
       });
 
-      const cachePolicy = cacheControlExtension.computeOverallCachePolicy();
+      const cachePolicy = computeOverallCachePolicy(hints);
       expect(cachePolicy).toHaveProperty('scope', CacheScope.Private);
     });
   });

packages/apollo-cache-control/src/__tests__/collectCacheControlHints.ts

@@ -1,38 +1,41 @@
 import { GraphQLSchema, graphql } from 'graphql';
-
-import {
-  enableGraphQLExtensions,
-  GraphQLExtensionStack,
-} from 'graphql-extensions';
 import {
-  CacheControlExtension,
   CacheHint,
   CacheControlExtensionOptions,
+  plugin,
 } from '../';
+import pluginTestHarness from 'apollo-server-core/dist/utils/pluginTestHarness';
 
 export async function collectCacheControlHints(
   schema: GraphQLSchema,
   source: string,
   options?: CacheControlExtensionOptions,
 ): Promise<CacheHint[]> {
-  enableGraphQLExtensions(schema);
 
   // Because this test helper looks at the formatted extensions, we always want
-  // to include them.
-  const cacheControlExtension = new CacheControlExtension({
+  // to include them in the response rather than allow them to be stripped
+  // out.
+  const pluginInstance = plugin({
     ...options,
     stripFormattedExtensions: false,
   });
 
-  const response = await graphql({
+  const requestContext = await pluginTestHarness({
+    pluginInstance,
     schema,
-    source,
-    contextValue: {
-      _extensionStack: new GraphQLExtensionStack([cacheControlExtension]),
+    graphqlRequest: {
+      query: source,
     },
+    executor: async (requestContext) => {
+      return await graphql({
+        schema,
+        source: requestContext.request.query,
+        contextValue: requestContext.context,
+      });
+    }
   });
 
-  expect(response.errors).toBeUndefined();
+  expect(requestContext.response.errors).toBeUndefined();
 
-  return cacheControlExtension.format()[1].hints;
+  return requestContext.response.extensions!.cacheControl.hints;
 }