Merge pull request #8643 from apollographql/issue-8639-nested-keyFiel…

…ds-problem

Fix error thrown by nested `keyFields: ["a", ["b", "c"], "d"]` syntax when some of the fields are aliased

CHANGELOG.md

@@ -1,3 +1,10 @@
+## Apollo Client 3.4.8 (not yet released)
+
+### Bug Fixes
+
+- Fix error thrown by nested `keyFields: ["a", ["b", "c"], "d"]` type policies when writing results into the cache where any of the key fields (`.a`, `.a.b`, `.a.c`, or `.d`) have been renamed by query field alias syntax. <br/>
+  [@benjamn](https://github.com/benjamn) in [#8643](https://github.com/apollographql/apollo-client/pull/8643)
+
 ## Apollo Client 3.4.7
 
 ### Bug Fixes

src/cache/inmemory/__tests__/policies.ts

@@ -129,6 +129,63 @@ describe("type policies", function () {
     checkAuthorName(cache);
   });
 
+  it("can specify nested keyFields with alias", function () {
+    const cache = new InMemoryCache({
+      typePolicies: {
+        Book: {
+          keyFields: ["title", "author", ["name"]],
+        },
+      },
+    });
+
+    const aliasQuery = gql`
+      query {
+        book {
+          title
+          writer: author {
+            alias: name
+          }
+        }
+      }
+    `;
+
+    const { author, ...rest } = theInformationBookData;
+    const aliasBookData = {
+      ...rest,
+      writer: {
+        alias: author.name,
+      },
+    };
+
+    cache.writeQuery({
+      query: aliasQuery,
+      data: {
+        book: aliasBookData,
+      },
+    });
+
+    expect(cache.extract(true)).toEqual({
+      ROOT_QUERY: {
+        __typename: "Query",
+        book: {
+          __ref: 'Book:{"title":"The Information","author":{"name":"James Gleick"}}',
+        },
+      },
+      'Book:{"title":"The Information","author":{"name":"James Gleick"}}': {
+        __typename: "Book",
+        title: "The Information",
+        // Note that "author" and "name" are stored internally, since they are
+        // the true names of their fields (according to the schema), despite the
+        // writer:author and alias:name aliases.
+        author: {
+          name: "James Gleick"
+        },
+      },
+    });
+
+    checkAuthorName(cache);
+  });
+
   it("keeps keyFields in specified order", function () {
     const cache = new InMemoryCache({
       typePolicies: {

src/cache/inmemory/policies.ts

@@ -1067,22 +1067,30 @@ function computeKeyObject(
   // so we are careful to build keyObj in the order of keys given in
   // specifier.
   const keyObj = Object.create(null);
-  let prevKey: string | undefined;
+
+  // The lastResponseKey variable tracks keys as seen in actual GraphQL response
+  // objects, potentially affected by aliasing. The lastActualKey variable
+  // tracks the corresponding key after removing aliases.
+  let lastResponseKey: string | undefined;
+  let lastActualKey: string | undefined;
+
   specifier.forEach(s => {
     if (Array.isArray(s)) {
-      if (typeof prevKey === "string") {
+      if (typeof lastActualKey === "string" &&
+          typeof lastResponseKey === "string") {
         const subsets = aliasMap && aliasMap.subsets;
-        const subset = subsets && subsets[prevKey];
-        keyObj[prevKey] = computeKeyObject(response[prevKey], s, strict, subset);
+        const subset = subsets && subsets[lastActualKey];
+        keyObj[lastActualKey] =
+          computeKeyObject(response[lastResponseKey], s, strict, subset);
       }
     } else {
       const aliases = aliasMap && aliasMap.aliases;
       const responseName = aliases && aliases[s] || s;
       if (hasOwn.call(response, responseName)) {
-        keyObj[prevKey = s] = response[responseName];
+        keyObj[lastActualKey = s] = response[lastResponseKey = responseName];
       } else {
         invariant(!strict, `Missing field '${responseName}' while computing key fields`);
-        prevKey = void 0;
+        lastResponseKey = lastActualKey = void 0;
       }
     }
   });