fetchMore overrides the variables without respecting nested items

[ps173]

Issue Description

variables with nested items are overriden when fetchMore is performed. I am not sure whether this issue has already been reported or not but I couldn't find it anywhere in repo so far.

for example

  const { data, fetchMore } = useQuery(MY_QUERY, {
    variables: {
      parentVariable: {
        a: "some_value",
      },
    },
  });

  // in fetch more
  async function fetchMoreItems() {
    await fetchMore({
      variables: {
        parentVariable: {
          // here instead of `a` some other value is passed. 
          // so new value of parentVariable will be 
          // { b : "some_value" } rather than { a: "some_value", b: "some_value" }
          b: "some_value"
        }
      },

      // concat items, can be ignored
      updateQuery: (previousResult, { fetchMoreResult }) => {
        const newEdges = fetchMoreResult?.people ?? [];
        const oldEdges = previousResult?.people ?? [];

        return {
          people: [...oldEdges, ...newEdges],
        };
      },
    });
  }
}

Although the doc says merged but docs don't really say that nested objects will be overriden with new value.
This might be intended and does make sense but should be documented

Link to Reproduction

https://codesandbox.io/p/devbox/practical-wozniak-d6mxd4?workspaceId=b0cc520f-8431-4414-9657-24f9bb60a21b

Reproduction Steps

No response

@apollo/client version

3.5.6

[jerelmiller]

Hey @ps173 👋

Thats a good callout about the docs. The merge that happens is a shallow merge so what you're seeing is expected. I've opened #12080 to make it a bit clearer in the docs that variable merging is a shallow merge.

[github-actions]

Do you have any feedback for the maintainers? Please tell us by taking a one-minute survey. Your responses will help us understand Apollo Client usage and allow us to serve you better.

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.
For general questions, we recommend using StackOverflow or our discord server.