Test key: ["@directive"] field policies.

src/cache/inmemory/__tests__/policies.ts

@@ -1163,6 +1163,117 @@ describe("type policies", function () {
       });
     }));
 
+    // Use several different directives to prove we're not hard-coding support
+    // for the @connection directive.
+    ["connection",
+     "directive",
+     "misdirective",
+    ].forEach(directiveName => it(`can refer to directive @${
+      directiveName
+    } in field key shorthand array`, function () {
+      const cache = new InMemoryCache({
+        typePolicies: {
+          Query: {
+            fields: {
+              feed: {
+                key: ["@" + directiveName, ["key"], "arg"],
+              },
+            },
+          },
+        },
+      });
+
+      const helloTokens = [
+        { __typename: "Token", text: "Hello" },
+        { __typename: "Token", text: "World" },
+        { __typename: "Token", text: "!" },
+      ];
+
+      cache.writeQuery({
+        query: gql`
+          query FeedQuery($num: Int) {
+            feed(arg: $num) @${directiveName}(key: "asdf", ignored: "boo") {
+              text
+            }
+          }
+        `,
+        variables: {
+          num: 1234,
+        },
+        data: {
+          feed: helloTokens,
+        },
+      });
+
+      expect(cache.extract()).toEqual({
+        ROOT_QUERY: {
+          "__typename": "Query",
+          [`feed:{"@${directiveName}":{"key":"asdf"},"arg":1234}`]: helloTokens,
+        },
+      });
+
+      const farewellTokens = [
+        { __typename: "Token", text: "farewell" },
+        { __typename: "Token", text: "cruel" },
+        { __typename: "Token", text: "world" },
+      ];
+
+      cache.writeQuery({
+        query: gql`
+          query FeedQuery($num: Int) {
+            feed(arg: $num) {
+              text
+            }
+          }
+        `,
+        variables: {
+          num: 2345,
+        },
+        data: {
+          feed: farewellTokens,
+        },
+      });
+
+      expect(cache.extract()).toEqual({
+        ROOT_QUERY: {
+          "__typename": "Query",
+          [`feed:{"@${directiveName}":{"key":"asdf"},"arg":1234}`]: helloTokens,
+          'feed:{"arg":2345}': farewellTokens,
+        },
+      });
+
+      const directivesTokens = [
+        { __typename: "Token", text: "directives" },
+        { __typename: "Token", text: "consuming" },
+        { __typename: "Token", text: "variables" },
+      ];
+
+      cache.writeQuery({
+        query: gql`
+          query FeedQuery($num: Int) {
+            feed @${directiveName}(key: $num, ignored: "boo") {
+              text
+            }
+          }
+        `,
+        variables: {
+          num: 3456,
+        },
+        data: {
+          feed: directivesTokens,
+        },
+      });
+
+      expect(cache.extract()).toEqual({
+        ROOT_QUERY: {
+          "__typename": "Query",
+          [`feed:{"@${directiveName}":{"key":"asdf"},"arg":1234}`]: helloTokens,
+          'feed:{"arg":2345}': farewellTokens,
+          [`feed:{"@${directiveName}":{"key":3456}}`]: directivesTokens,
+        },
+      });
+    }));
+
     it("can use options.storage in read functions", function () {
       const storageSet = new Set<Record<string, any>>();