I’m working with a team that are running (relatively) old versions of Elixir and Erlang. Last month I added dialyzer, via dialyxir (can never spell that) to their build. Today we are running into an issue:

:dialyzer.run error: Old PLT file /apps/[redacted]/priv/plts/application.plt

The build is on Azure. The PLTs are cached using Azure Pipeline caching (here if you want to know but I wouldn’t if I could avoid it).

Dialyxir config is

  defp dialyzer do
    [
      plt_add_apps: [:mix, :ex_insights],
      plt_file: {:no_warn, "priv/plts/application.plt"},
      ignore_warnings: "dialyzer.ignore_warnings"
    ]
  end

The plts are excluded from source control.

Versions:

elixir 1.14.2-otp-25
erlang 25.3.2.6

I know I can fix the issue by invalidating the cache but I would like to understand how it happened in the first place. The only thing I’ve been able to find is this somewhat cryptic Erlang mailing list q&a. Old PLT file? .

The checking is going on here which looks like there is some discrepancy between an internally held hash in the PLT and the file contents.

Thoughts?