What warnings? Where do they appear? I ask because I’ve seen plenty of very strange messages in-editor when elixir-ls gets confused, but those usually disappear after cleaning _build etc and don’t show up in mix dialyzer.

I personally have dialyzer disabled in my vscode-elixirls settings because I find the warnings very distracting for WIP code. When I am closer to a final version, I run it on the command line to check my assumptions and catch things I missed.

I took in the replies I got and learned that I was trying a bit too hard. So i loosened up trying to cram everything into a specific type in the api-module. Refactored the whole thing, in a way that means I have to do a little more work over each function, but have more control. Using the mix dialyzer allowed be to see the errors more clearly in the shell, than as small windows in VS Code.
The hint, that dialyser is usually right made me follow the advice to get a better picture of what iot wanted. And it worked. Thanks.

Fun thing about elixir_ls is that it doesn’t compile to ./_build, but to ./.elixir_ls (specifically ./elixir_ls/build/test). I don’t think I’m alone in occasionally zapping the .elixir_ls directory.

Another fun thing is that dialyzer is almost always correct although often cryptic. (When I say fun, I really mean infuriating.)

As @hlx says, I’d be inclined to also include dialyxir as a dependency (only: [:dev, :test], runtime: false) so you can run mix dialyzer from the terminal and fix the errors, eg with the capitalisation typo MySpaceIPFS instead of MyspaceIPFS, eg here

Also as @hlx alludes {:ok,MyspaceIpfs.RootCid}should probably be{:ok, :MyspaceIpfs.RootCid.t()}` (which I see you’ve defined in the struct).