TypePolicy is broken Or there is no clear documentation about it.

[ebsangam]

I am trying to merge paginated result into the cache but it very difficult to implement and eventually it does not work. I am facing following issue and don't know how to solve.

• TypePolicy are not type safe. Everything is dynamic hence makes it difficult to implement.
• After successfully adding TypePolicy, the merge function does not work as expected and it throws PartialDataException.

• After adding ReadPolicy it does solve PartialDataException but throws type error as internally ferry tries to type cast a List of object as String.

  I have this example to reproduce the issue. https://github.com/ebsangam/graphql_caching

[knaeckeKami]

The repro does have non-public dependencies, I can't run it. It's also very big and has a lot of files and architecture. It also does not seem to actually use any type policies. Could you reproduce a more minimal example?

Or just show, with what data does the merge function get called, how do you merge them, and how does the exception get triggered?

[ebsangam]

Thank you for quick response. I will provide you minimal example.

[ebsangam]

I have pushed a new branch without local dependency. https://github.com/ebsangam/graphql_caching/tree/minimal-example This still has uses injectable/get_it for DI. I should run on you machine. Let me know if I need to remove injectable/get_it too.

[knaeckeKami]

What are the steps to reproduce the issue?

[ebsangam]

I have just updated the branch and removed all dependencies to third party packages that was not needed to reproduce the issue. https://github.com/ebsangam/graphql_caching/tree/minimal-example To reproduce:

• open the app, it will load page 1
• press floating button, it will load page 2 It will throw PartialDataException.

[ebsangam]

Be sure to pull the latest changes.

[ebsangam]

@knaeckeKami also uncomment typePolicies in /ferry/client.dart. I missed to uncomment.

[knaeckeKami]

I can't seem to get it working. but I think you return a list of posts in your merge callback, when you should return a map that matches PostPage

[ebsangam]

Oh thanks. Solved. I am dumb to forget this when using dynamic types.

[ebsangam]

However we can make another ticket to make type policy type safe. It is too hard to work with dynamic types. What do you think?

[knaeckeKami]

you can create a ticket, but I don't see how fieldpolicies could be made typesafe.

[ebsangam]

Ok for now I am closing this issue. Thanks for your help.