iodata handling

[JonasGruenwald]

Hello! I noticed when trying to snapshot the body of an outgoing HTTP request, that mneme will crash with a kind of vague error when given iodata.

Reproduction case:

  test "iodata snapshot" do
    wibble = %{
      "wobble" => 1
    }
    |> Jason.encode_to_iodata!()
    auto_assert wibble
  end

Error:

1) test iodata snapshot (Backend.SomeTest)
   test/backend/some_test.exs:6
   ** (Mneme.InternalError) Mneme encountered an internal error. This is likely a bug in Mneme.

   Please consider reporting this error at https://github.com/zachallaun/mneme/issues. Thanks!

   ** (FunctionClauseError) no function clause matching in Enum."-map_reduce/3-lists^mapfoldl/2-0-"/3
       (elixir 1.17.3) lib/enum.ex:1829: Enum."-map_reduce/3-lists^mapfoldl/2-0-"(#Function<3.54260353/2 in Mneme.Assertion.PatternBuilder.enum_to_patterns/3>, [], "wobble")
       (elixir 1.17.3) lib/enum.ex:1829: Enum."-map_reduce/3-lists^mapfoldl/2-0-"/3
       (mneme 0.10.0) lib/mneme/assertion/pattern_builder.ex:281: Mneme.Assertion.PatternBuilder.enum_to_patterns/3
       (mneme 0.10.0) lib/mneme/assertion/pattern_builder.ex:78: Mneme.Assertion.PatternBuilder.do_to_patterns/3
       (mneme 0.10.0) lib/mneme/assertion/pattern_builder.ex:21: Mneme.Assertion.PatternBuilder.to_patterns/3
       (elixir 1.17.3) lib/enum.ex:1829: Enum."-map_reduce/3-lists^mapfoldl/2-0-"/3
       (elixir 1.17.3) lib/enum.ex:1829: Enum."-map_reduce/3-lists^mapfoldl/2-0-"/3
       (mneme 0.10.0) lib/mneme/assertion/pattern_builder.ex:281: Mneme.Assertion.PatternBuilder.enum_to_patterns/3
       (mneme 0.10.0) lib/mneme/assertion/pattern_builder.ex:78: Mneme.Assertion.PatternBuilder.do_to_patterns/3
       (mneme 0.10.0) lib/mneme/assertion/pattern_builder.ex:21: Mneme.Assertion.PatternBuilder.to_patterns/3
       (mneme 0.10.0) lib/mneme/assertion/pattern_builder.ex:16: Mneme.Assertion.PatternBuilder.to_patterns/2
       (mneme 0.10.0) lib/mneme/assertion.ex:360: Mneme.Assertion.build_and_select_pattern/2
       (mneme 0.10.0) lib/mneme/assertion.ex:301: Mneme.Assertion.generate_patterns/1
       (mneme 0.10.0) lib/mneme/patcher.ex:142: Mneme.Patcher.prepare_assertion/2
       (mneme 0.10.0) lib/mneme/patcher.ex:66: Mneme.Patcher.patch!/3
       (elixir 1.17.3) lib/task/supervised.ex:101: Task.Supervised.invoke_mfa/2
       (elixir 1.17.3) lib/task/supervised.ex:36: Task.Supervised.reply/4

   
   code: auto_assert wibble
   stacktrace:
     (mneme 0.10.0) lib/mneme/assertion.ex:242: Mneme.Assertion.handle_assertion/4
     (mneme 0.10.0) lib/mneme/assertion.ex:179: Mneme.Assertion.run!/3
     test/backend/some_test.exs:11: (test)

The error is also the same if the iodata is not passed directly to auto_assert but inside of a struct/map.

Would be great if mneme could automatically convert iodata to string like IO.inspect does and snapshot the string, or otherwise would be nice to have an error that's more clear about what's wrong with the given input data.

[zachallaun]

Thanks for the report! This is definitely a bug -- something in Mneme's pattern generation doesn't like this. If you're able to IO.inspect the iodata and share it here, that will be helpful to reproduce.

In the meantime, I'd recommend to_string to assert on it, but I'll get this fixed asap.

[zachallaun]

I'm silly, you have a simple example there already. Will get it fixed.

[zachallaun]

@JonasGruenwald Would you mind giving main a shot and making sure this is now working as expected?

{:mneme, github: "zachallaun/mneme", ref: "main"}

[JonasGruenwald]

Yeah that works, thanks for your quick work @zachallaun !

[zachallaun]

Great to hear! I'll cut a release shortly. (Edit: Included in v0.10.1)