Allow writeFragment to infer ROOT_QUERY based on data.__typename.

#6495 (comment)
apollographql · Jun 26, 2020 · 6eb8d13 · 6eb8d13
1 parent 877c560
commit 6eb8d13
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diff --git a/src/cache/inmemory/__tests__/writeToStore.ts b/src/cache/inmemory/__tests__/writeToStore.ts
@@ -12,6 +12,7 @@ import gql from 'graphql-tag';
 import {
   storeKeyNameFromField,
   makeReference,
+  isReference,
 } from '../../../utilities/graphql/storeUtils';
 import { addTypenameToDocument } from '../../../utilities/graphql/transform';
 import { cloneDeep } from '../../../utilities/common/cloneDeep';
@@ -2302,4 +2303,26 @@ describe('writing to the store', () => {
       },
     });
   });
+
+  it("writeFragment should be able to infer ROOT_QUERY", () => {
+    const cache = new InMemoryCache;
+
+    const ref = cache.writeFragment({
+      fragment: gql`fragment RootField on Query { field }`,
+      data: {
+        __typename: "Query",
+        field: "value",
+      },
+    });
+
+    expect(isReference(ref)).toBe(true);
+    expect(ref!.__ref).toBe("ROOT_QUERY");
+
+    expect(cache.extract()).toEqual({
+      ROOT_QUERY: {
+        __typename: "Query",
+        field: "value",
+      },
+    });
+  });
 });
diff --git a/src/cache/inmemory/policies.ts b/src/cache/inmemory/policies.ts
@@ -275,6 +275,11 @@ export class Policies {
       ? getTypenameFromResult(object, selectionSet, fragmentMap)
       : object.__typename;
 
+    if (typename) {
+      const rootId = this.rootIdsByTypename[typename];
+      if ("string" === typeof rootId) return [rootId];
+    }
+
     const context: KeyFieldsContext = {
       typename,
       selectionSet,