Fix relayStylePagination to better support existing and incoming without edges property

src/cache/inmemory/__tests__/__snapshots__/policies.ts.snap

@@ -824,7 +824,6 @@ Object {
         "__typename": "PageInfo",
         "endCursor": "YXJyYXljb25uZWN0aW9uOjI=",
         "hasNextPage": true,
-        "hasPreviousPage": false,
         "startCursor": "YXJyYXljb25uZWN0aW9uOjI=",
       },
       "totalCount": 1292,
@@ -861,7 +860,6 @@ Object {
         "__typename": "PageInfo",
         "endCursor": "YXJyYXljb25uZWN0aW9uOjI=",
         "hasNextPage": true,
-        "hasPreviousPage": false,
         "startCursor": "YXJyYXljb25uZWN0aW9uOjI=",
       },
       "totalCount": 1293,

src/cache/inmemory/__tests__/policies.ts

@@ -3220,13 +3220,6 @@ describe("type policies", function () {
           ROOT_QUERY: {
             __typename: "Query",
             todos: {
-              edges: [],
-              pageInfo: {
-                "endCursor": "",
-                "hasNextPage": true,
-                "hasPreviousPage": false,
-                "startCursor": "",
-               },
                totalCount: 1292
              },
           }

src/utilities/policies/__tests__/relayStylePagination.test.ts

@@ -109,8 +109,21 @@ describe('relayStylePagination', () => {
         hasNextPage: true,
       });
     });
+
+    it("should not return empty edges if none existing", () => {
+      const resultWithTotalCount = policy.read!({
+        totalCount: 10
+      }, fakeReadOptions);
+
+      expect(
+        resultWithTotalCount,
+      ).toEqual({
+        totalCount: 10,
+      });
+    });
   });
 
+
   describe('merge', () => {
     const merge = policy.merge;
     // The merge function should exist, make TS aware
@@ -143,7 +156,6 @@ describe('relayStylePagination', () => {
       };
       const result = merge(undefined, incoming, options);
       expect(result).toEqual({
-        edges: [],
         pageInfo: {
           hasPreviousPage: false,
           hasNextPage: true,
@@ -236,6 +248,92 @@ describe('relayStylePagination', () => {
       expect(result).toEqual(fakeExisting);
     })
 
+    describe('when incoming has no edges', () => {
+      it('should not replace existing null with empty edges', () => {
+        const fakeExisting = null;
+
+        const fakeIncoming = {
+          totalCount: 10
+        };
+
+        const fakeOptions = {
+          ...options,
+        };
+
+        const result = merge(
+          fakeExisting,
+          fakeIncoming,
+          fakeOptions,
+        );
+
+        expect(result).toEqual({
+          totalCount: 10
+        });
+      })
+
+      it('should not merge existing with empty edges', () => {
+        const fakeExisting = {
+          totalCount: 10
+        };
+
+        const fakeIncoming = {
+          totalCount: 11
+        };
+
+        const fakeOptions = {
+          ...options,
+          args: {
+            after: 'alpha',
+          },
+        };
+
+        const result = merge(
+          fakeExisting,
+          fakeIncoming,
+          fakeOptions,
+        );
+
+        expect(result).toEqual({
+          totalCount: 11
+        });
+      })
+    })
+
+    describe('when existing has no edges', () => {
+      it('should add incoming edges', () => {
+        const fakeExisting = {
+          totalCount: 10
+        };
+
+        const incomingEdges = [
+          { cursor: 'alpha', node: makeReference("fakeAlpha") },
+        ];
+        const incoming = {
+          edges: incomingEdges,
+          pageInfo: {
+            hasPreviousPage: false,
+            hasNextPage: true,
+            startCursor: 'alpha',
+            endCursor: 'alpha'
+          },
+        };
+        const fakeOptions = {
+          ...options,
+        };
+
+        const result = merge(
+          fakeExisting,
+          incoming,
+          fakeOptions,
+        );
+
+        expect(result).toEqual({
+          ...incoming,
+          totalCount: 10
+        });
+      })
+    })
+
     it('should replace existing null with incoming', () => {
       const incomingEdges = [
         { cursor: 'alpha', node: makeReference("fakeAlpha") },