Typescript error when compiling a module using apollo-client and apollo-cache-inmemory

Intended outcome:

Successful compilation of the project.

Actual outcome:

ERROR in [at-loader] ./node_modules/apollo-cache-inmemory/lib/inMemoryCache.d.ts:5:22
    TS2415: Class 'InMemoryCache' incorrectly extends base class 'ApolloCache<NormalizedCacheObject>'.
  Types of property 'read' are incompatible.
    Type '<T>(query: ReadOptions) => T | null' is not assignable to type '<T>(query: ReadOptions) => T'.
      Type 'T | null' is not assignable to type 'T'.
        Type 'null' is not assignable to type 'T'.

How to reproduce the issue: tsconfig.json

{
  "compilerOptions": {
    "sourceMap": true,
    "jsx": "preserve",
    "target": "es2015",
    "lib": ["es2017", "dom", "esnext.asynciterable"],
    "module": "es2015",
    "moduleResolution": "node",
    "noImplicitAny": true,
    "noImplicitThis": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "strictNullChecks": true,
    "allowSyntheticDefaultImports": false,
    "baseUrl": ".",
    "paths": {
    }
  },
  "include": [
    "src/**/*.ts",
    "src/**/*.tsx"
  ],
  "exclude": [
    "node_modules"
  ]
}

Sample module:

import { InMemoryCache } from "apollo-cache-inmemory";
import { ApolloClient, ApolloQueryResult } from "apollo-client";
import { HttpLink } from "apollo-link-http";
import gql from "graphql-tag";

const client = new ApolloClient({
  cache: new InMemoryCache() as any,
  link: new HttpLink({ uri: process.env.GRAPHQL_ENDPOINT })
});

Version

• apollo-client@2.0.2
• apollo-cache-inmemory@^1.1.0
• apollo-cache@^1.0.0

** Possible cause **

apollo-cache defines ApolloCache base class with read method which cannot miss:

abstract read<T>(query: Cache.ReadOptions): T

apollo-cache-inmemory actually has more realistic definition of the return value as T | null

[mbrochh]

Am I right to assume that this is still not fixed? I have this code:

    const client = new ApolloClient({
      cache: new InMemoryCache(),
      link: batchHttpLink,
      queryDeduplication: true,
      ssrMode: true,
    })

and am getting this TS error:

Type 'InMemoryCache' is not assignable to type 'ApolloCache<NormalizedCacheObject>'.
  Property 'data' is protected in type 'InMemoryCache' but public in type 'ApolloCache<NormalizedCacheObject>'. [2322]

[tackley]

Temporary, and unfortunate, workaround is to set "strictNullChecks": false 😞