Reuse observables in client.watchFragment as much as possible (#13026)

Author: jerelmiller

.api-reports/api-report-core.api.md

@@ -1160,7 +1160,7 @@ export type WatchQueryOptions<TVariables extends OperationVariables = OperationV
 
 // Warnings were encountered during analysis:
 //
-// src/core/ApolloClient.ts:370:5 - (ae-forgotten-export) The symbol "NextFetchPolicyContext" needs to be exported by the entry point index.d.ts
+// src/core/ApolloClient.ts:371:5 - (ae-forgotten-export) The symbol "NextFetchPolicyContext" needs to be exported by the entry point index.d.ts
 // src/core/ObservableQuery.ts:368:5 - (ae-forgotten-export) The symbol "QueryManager" needs to be exported by the entry point index.d.ts
 // src/core/QueryManager.ts:180:5 - (ae-forgotten-export) The symbol "MutationStoreValue" needs to be exported by the entry point index.d.ts
 

.api-reports/api-report.api.md

@@ -2782,13 +2782,13 @@ interface WriteContext extends ReadMergeModifyContext {
 
 // Warnings were encountered during analysis:
 //
-// src/cache/core/cache.ts:123:11 - (ae-forgotten-export) The symbol "MissingTree" needs to be exported by the entry point index.d.ts
+// src/cache/core/cache.ts:127:11 - (ae-forgotten-export) The symbol "MissingTree" needs to be exported by the entry point index.d.ts
 // src/cache/inmemory/policies.ts:98:3 - (ae-forgotten-export) The symbol "FragmentMap" needs to be exported by the entry point index.d.ts
 // src/cache/inmemory/policies.ts:167:3 - (ae-forgotten-export) The symbol "KeySpecifier" needs to be exported by the entry point index.d.ts
 // src/cache/inmemory/policies.ts:167:3 - (ae-forgotten-export) The symbol "KeyArgsFunction" needs to be exported by the entry point index.d.ts
 // src/cache/inmemory/types.ts:134:3 - (ae-forgotten-export) The symbol "KeyFieldsFunction" needs to be exported by the entry point index.d.ts
-// src/core/ApolloClient.ts:168:5 - (ae-forgotten-export) The symbol "IgnoreModifier" needs to be exported by the entry point index.d.ts
-// src/core/ApolloClient.ts:370:5 - (ae-forgotten-export) The symbol "NextFetchPolicyContext" needs to be exported by the entry point index.d.ts
+// src/core/ApolloClient.ts:169:5 - (ae-forgotten-export) The symbol "IgnoreModifier" needs to be exported by the entry point index.d.ts
+// src/core/ApolloClient.ts:371:5 - (ae-forgotten-export) The symbol "NextFetchPolicyContext" needs to be exported by the entry point index.d.ts
 // src/core/ObservableQuery.ts:368:5 - (ae-forgotten-export) The symbol "QueryManager" needs to be exported by the entry point index.d.ts
 // src/core/QueryManager.ts:180:5 - (ae-forgotten-export) The symbol "MutationStoreValue" needs to be exported by the entry point index.d.ts
 // src/local-state/LocalState.ts:149:5 - (ae-forgotten-export) The symbol "LocalState" needs to be exported by the entry point index.d.ts

.changeset/tiny-pumas-compete.md

@@ -0,0 +1,5 @@
+---
+"@apollo/client": patch
+---
+
+Reduce the number of observables created by `watchFragment` by reusing existing observables as much as possible. This should improve performance when watching the same item in the cache multiple times after a cache update occurs.

.size-limits.json

@@ -1,6 +1,6 @@
 {
-  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (CJS)": 45558,
-  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (production) (CJS)": 40136,
-  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\"": 34576,
-  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (production)": 28375
+  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (CJS)": 45655,
+  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (production) (CJS)": 40280,
+  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\"": 34667,
+  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (production)": 28498
 }