Set result.partial only if true in getCurrentResult.

If result.partial is logically false, letting it remain undefined (and
thus falsy) is also allowed by the ?:boolean type of the field. We should
be consistent about omitting the partial field when it's falsy, unless we
want to be consistent about making it always either true or false, which
would likely be a more disruptive change.

src/core/ObservableQuery.ts

@@ -141,7 +141,9 @@ export class ObservableQuery<
     const { fetchPolicy = 'cache-first' } = this.options;
     if (fetchPolicy === 'no-cache' ||
         fetchPolicy === 'network-only') {
-      result.partial = false;
+      // Similar to setting result.partial to false, but taking advantage
+      // of the falsiness of missing fields.
+      delete result.partial;
     } else if (
       !result.data ||
       // If this.options.query has @client(always: true) fields, we cannot
@@ -154,20 +156,23 @@ export class ObservableQuery<
       !this.queryManager.transform(this.options.query).hasForcedResolvers
     ) {
       const diff = this.queryInfo.getDiff();
-      result.partial = !diff.complete;
       result.data = (
         diff.complete ||
         this.options.returnPartialData
       ) ? diff.result : void 0;
-      // If the cache diff is complete, and we're using a FetchPolicy that
-      // terminates after a complete cache read, we can assume the next
-      // result we receive will have NetworkStatus.ready and !loading.
-      if (diff.complete &&
-          result.networkStatus === NetworkStatus.loading &&
-          (fetchPolicy === 'cache-first' ||
-           fetchPolicy === 'cache-only')) {
-        result.networkStatus = NetworkStatus.ready;
-        result.loading = false;
+      if (diff.complete) {
+        // If the diff is complete, and we're using a FetchPolicy that
+        // terminates after a complete cache read, we can assume the next
+        // result we receive will have NetworkStatus.ready and !loading.
+        if (result.networkStatus === NetworkStatus.loading &&
+            (fetchPolicy === 'cache-first' ||
+             fetchPolicy === 'cache-only')) {
+          result.networkStatus = NetworkStatus.ready;
+          result.loading = false;
+        }
+        delete result.partial;
+      } else {
+        result.partial = true;
       }
     }
 

src/core/__tests__/ObservableQuery.ts

@@ -1361,7 +1361,6 @@ describe('ObservableQuery', () => {
           data: dataOne,
           loading: false,
           networkStatus: 7,
-          partial: false,
         });
         resolve();
       });
@@ -1406,7 +1405,6 @@ describe('ObservableQuery', () => {
           data: dataOne,
           loading: false,
           networkStatus: NetworkStatus.ready,
-          partial: false,
         });
       }).then(resolve, reject);
     });
@@ -1502,7 +1500,7 @@ describe('ObservableQuery', () => {
       const queryManager = mockQueryManager(reject, {
         request: { query, variables },
         result: { data: dataOne, errors: [error] },
-      }, 
+      },
       // FIXME: We shouldn't need a second mock, there should only be one network request
       {
         request: { query, variables },
@@ -1651,15 +1649,13 @@ describe('ObservableQuery', () => {
           data: void 0,
           loading: true,
           networkStatus: 1,
-          partial: false,
         });
 
         subscribeAndCount(reject, observable, (handleCount, subResult) => {
           if (handleCount === 1) {
             expect(subResult).toEqual({
               loading: true,
               networkStatus: NetworkStatus.loading,
-              partial: false,
             });
           } else if (handleCount === 2) {
             expect(subResult).toEqual({
@@ -1696,7 +1692,6 @@ describe('ObservableQuery', () => {
           data: undefined,
           loading: true,
           networkStatus: 1,
-          partial: false,
         });
 
         subscribeAndCount(reject, observable, (handleCount, subResult) => {
@@ -1711,7 +1706,6 @@ describe('ObservableQuery', () => {
               data,
               loading,
               networkStatus,
-              partial: false,
             });
           } else if (handleCount === 2) {
             expect(stripSymbols(subResult)).toEqual({