AC3: Memory leak in mutation retains context object in memory on mutation failure

[kamilkisiela]

Intended outcome:
Object passed as context to mutate method should be released when Promise is settled, instead of being retrained in memory.

The MutationStore holds a reference to an Error forever, it never gets deleted and it's never accessed anywhere in Apollo Client, just in Dev Tools. So I think, if connectToDevTools are disabled (or NODE_ENV === 'production' or typeof window === 'undefined) then storing an Error in MutationStore` no longer makes sense.

Actual outcome:
context object is retained in memory by AC3.

How to reproduce the issue:
Use mutate with context set. Apollo keeps reference to that object even when mutation is done, and promise is settled (and all references has been destructed).

You can find a complete reproduction (as a Jest test) here:
https://github.com/dotansimha/apollo-very-pessimism/tree/mutation

Instruction:

yarn --force
yarn test

I also used patch-package that represents my PR with a fix, to enable it, please modify package.json

  "scripts": {
-    "disabled:postinstall": "patch-package",
+    "postinstall": "patch-package",

And run

yarn --force
yarn test

Versions

  System:
    OS: macOS 10.15.7
  Binaries:
    Node: 10.18.0 - ~/.nvm/versions/node/v10.18.0/bin/node
    Yarn: 1.22.4 - ~/.yarn/bin/yarn
    npm: 6.13.4 - ~/.nvm/versions/node/v10.18.0/bin/npm
  Browsers:
    Chrome: 86.0.4240.75
    Edge: 86.0.622.38
    Firefox: 79.0
    Safari: 14.0
  npmPackages:
    @apollo/client: 3.2.4 => 3.2.4 

[kamilkisiela]

Continuation of #7149 (comment)

[benjamn]

@kamilkisiela These changes have been published in @apollo/client@3.3.0-beta.13, fyi.

[hwillson]

Fixed in @apollo/client@3.3.0 - thanks!