@apollo/client

To avoid retaining sensitive information from mutation root field arguments, Apollo Client v3.4 automatically clears any ROOT_MUTATION fields from the cache after each mutation finishes. If you need this information to remain in the cache, you can prevent the removal by passing the keepRootFields: true option to client.mutate. ROOT_MUTATION result data are also passed to the mutation update function, so we recommend obtaining the results that way, rather than using keepRootFields: true, if possible.

Internally, Apollo Client now controls the execution of development-only code using the __DEV__ global variable, rather than process.env.NODE_ENV. While this change should not cause any visible differences in behavior, it will increase your minified+gzip bundle size by more than 3.5kB, unless you configure your minifier to replace __DEV__ with a true or false constant, the same way you already replace process.env.NODE_ENV with a string literal like "development" or "production". For an example of configuring a Create React App project without ejecting, see this pull request for our React Apollo reproduction template.

Internally, Apollo Client now uses namespace syntax (e.g. import * as React from "react") for imports whose types are re-exported (and thus may appear in .d.ts files). This change should remove any need to configure esModuleInterop or allowSyntheticDefaultImports in tsconfig.json, but might require updating bundler configurations that specify named exports of the react and prop-types packages, to include exports like createContext and createElement (example).

Respect no-cache fetch policy (by not reading any data from the cache) for loading: true results triggered by notifyOnNetworkStatusChange: true.

The TypeScript return types of the getLastResult and getLastError methods of ObservableQuery now correctly include the possibility of returning undefined. If you happen to be calling either of these methods directly, you may need to adjust how the calling code handles the methods' possibly-undefined results.

Log non-fatal invariant.error message when fields are missing from result objects written into InMemoryCache, rather than throwing an exception. While this change relaxes an exception to be merely an error message, which is usually a backwards-compatible change, the error messages are logged in more cases now than the exception was previously thrown, and those new error messages may be worth investigating to discover potential problems in your application. The errors are not displayed for @client-only fields, so adding @client is one way to handle/hide the errors for local-only fields. Another general strategy is to use a more precise query to write specific subsets of data into the cache, rather than reusing a larger query that contains fields not present in the written data.

The nextFetchPolicy option for client.watchQuery and useQuery will no longer be removed from the options object after it has been applied, and instead will continue to be applied any time options.fetchPolicy is reset to another value, until/unless the options.nextFetchPolicy property is removed from options.

The fetchMore, subscribeToMore, and updateQuery functions returned from the useQuery hook may now return undefined in edge cases where the functions are called when the component is unmounted @noghartt in #7980.