So, I am working with my IPFS client library and I’ve run into dialyzer hell. The code is kinda working fine, but Dialyzer is not happy with me. Before I ignore it completely, I want to make sure I’m not guilty of an anti-pattern.

The IPFS API returns stuff like this:

{
  "BlocksReceived": "<uint64>",
  "BlocksSent": "<uint64>",
  "DataReceived": "<uint64>",
  "DataSent": "<uint64>",
  "DupBlksReceived": "<uint64>",
  "DupDataReceived": "<uint64>",
  "MessagesReceived": "<uint64>",
  "Peers": [
    "<string>"
  ],
  "ProvideBufLen": "<int>",
  "Wantlist": [
    {
      "/": "<cid-string>"
    }
  ]
}

I thought it would be nice to make structs for these types of return values, instead of just passing the JSON back to user. I have made structs to build these, where I have structs for wantlist and CIDs.
https://github.com/bahner/myspace-ipfs/blob/develop/lib/myspace_ipfs/structs/bitswap/wantlist.ex
https://github.com/bahner/myspace-ipfs/blob/develop/lib/myspace_ipfs/structs/common.ex

Then I use the structs as components for complex structs and so forth. I like the wantlist.keys notation that they give me when I structure the keys as (existing) atoms.

But when I take a result and pass it to Jason.decode, then dialyser becomes really unhappy. The error messages blow up in length, as I try to fix them. And, hence, I suspect I’m doing it wrong.

Please note. I can’t always use only use the Tesla.Middleware.Jason for this, as the API sometimes returns \n<\n when data is streamed, and there is no known end to the data, so it canæt generate lists, and hence not proper JSON.

Am I doing it wrong by trying to massage the data and should I just pass the JSON strings to the user? Or just let the middleware do its best and decode the lines as they come in.