previousResult is undefined when using updateQuery in fetchMore

Intended outcome: The previousResult variable should contain the previous data.

Actual outcome: The previousResult is undefined

How to reproduce the issue: I followed the tutorial on this page using the Relay-style cursor pagination. After switching everything to the latest stable apollo version the previousResult variable contains the data.

fetchMore({
          variables: {
            cursor: comments.pageInfo.endCursor
          },
          updateQuery: (previousResult, { fetchMoreResult }) => {
            const newEdges = fetchMoreResult.comments.edges;
            const pageInfo = fetchMoreResult.comments.pageInfo;

            // Apollo v3 Beta
           // previousResult is undefined

           // Apollo latest stable version
           // previousResult contains the data

            return newEdges.length
              ? {
                  // Put the new comments at the end of the list and update `pageInfo`
                  // so we have the new `endCursor` and `hasNextPage` values
                  comments: {
                    __typename: previousResult.comments.__typename,
                    edges: [...previousResult.comments.edges, ...newEdges],
                    pageInfo
                  }
                }
              : previousResult;
          }
        })

Versions v3.0.0-beta.20

[toddtarsi]

@Thomazella - Did you add a console logger in the area I recommended above? It sucks to add a logger there, but it helped me track down some issues that weren’t escaping in an obvious way. If using npm to install it, you’ll have to add it to the transpiled code, but it isn’t so bad. Also, feel free to ignore this if not using the InMemoryCache.

[nikhedonia]

I’m experiencing the same issue in @apollo/client@3.2.2 when using useQuery. Any updates on this issue? I’ve noticed also the error is not deterministic and seems to be related to network latency.

@soltysaleksandr workaround works but it would be nice if it would work out of the box