Fix cache policy calculation when a hint has maxAge 0 (#2197)

Fixes apollographql/apollo-cache-control#11.

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

@@ -0,0 +1,68 @@
+import { ResponsePath } from 'graphql';
+import { CacheControlExtension, CacheScope } from '../';
+
+describe('CacheControlExtension', () => {
+  let cacheControlExtension: CacheControlExtension;
+
+  beforeEach(() => {
+    cacheControlExtension = new CacheControlExtension();
+  });
+
+  describe('computeOverallCachePolicy', () => {
+    const responsePath: ResponsePath = {
+      key: 'test',
+      prev: undefined,
+    };
+    const responseSubPath: ResponsePath = {
+      key: 'subTest',
+      prev: responsePath,
+    };
+    const responseSubSubPath: ResponsePath = {
+      key: 'subSubTest',
+      prev: responseSubPath,
+    };
+
+    it('returns undefined without cache hints', () => {
+      const cachePolicy = cacheControlExtension.computeOverallCachePolicy();
+      expect(cachePolicy).toBeUndefined();
+    });
+
+    it('returns lowest max age value', () => {
+      cacheControlExtension.addHint(responsePath, { maxAge: 10 });
+      cacheControlExtension.addHint(responseSubPath, { maxAge: 20 });
+
+      const cachePolicy = cacheControlExtension.computeOverallCachePolicy();
+      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 });
+
+      const cachePolicy = cacheControlExtension.computeOverallCachePolicy();
+      expect(cachePolicy).toBeUndefined();
+    });
+
+    it('returns PUBLIC scope by default', () => {
+      cacheControlExtension.addHint(responsePath, { maxAge: 10 });
+
+      const cachePolicy = cacheControlExtension.computeOverallCachePolicy();
+      expect(cachePolicy).toHaveProperty('scope', CacheScope.Public);
+    });
+
+    it('returns PRIVATE scope if any cache hint has PRIVATE scope', () => {
+      cacheControlExtension.addHint(responsePath, {
+        maxAge: 10,
+        scope: CacheScope.Public,
+      });
+      cacheControlExtension.addHint(responseSubPath, {
+        maxAge: 10,
+        scope: CacheScope.Private,
+      });
+
+      const cachePolicy = cacheControlExtension.computeOverallCachePolicy();
+      expect(cachePolicy).toHaveProperty('scope', CacheScope.Private);
+    });
+  });
+});

packages/apollo-cache-control/src/index.ts

@@ -156,10 +156,11 @@ export class CacheControlExtension<TContext = any>
     let scope: CacheScope = CacheScope.Public;
 
     for (const hint of this.hints.values()) {
-      if (hint.maxAge) {
-        lowestMaxAge = lowestMaxAge
-          ? Math.min(lowestMaxAge, hint.maxAge)
-          : hint.maxAge;
+      if (hint.maxAge !== undefined) {
+        lowestMaxAge =
+          lowestMaxAge !== undefined
+            ? Math.min(lowestMaxAge, hint.maxAge)
+            : hint.maxAge;
       }
       if (hint.scope === CacheScope.Private) {
         scope = CacheScope.Private;