Bug in compile.protocols

[alco]

I'm adding consolidation to escript.build, and sometimes it fails after compiling all beams. Rerunning the task finished successfully.

λ mix escript.build
==> jazz
Compiled lib/jazz.ex
Compiled lib/jazz/parser.ex
Compiled lib/jazz/decoder.ex
Compiled lib/jazz/encoder.ex
Generated jazz.app
==> miniweb
Compiled lib/miniweb/handlers.ex
Compiled lib/mix/tasks/uweb.ex
Compiled lib/miniweb/cli/serve_cmd.ex
Compiled lib/miniweb/cli/inspect_cmd.ex
Compiled lib/miniweb/cli/cli.ex
Generated miniweb.app
** (MatchError) no match of right hand side value: {:error, :no_beam_info}
    (mix) lib/mix/tasks/compile.protocols.ex:53: Mix.Tasks.Compile.Protocols."-consolidate/3-lc$^0/1-0-"/3
    (mix) lib/mix/tasks/compile.protocols.ex:50: Mix.Tasks.Compile.Protocols.consolidate/3
    (mix) lib/mix/tasks/compile.protocols.ex:38: Mix.Tasks.Compile.Protocols.run/1
    (mix) lib/mix/tasks/escript.build.ex:99: Mix.Tasks.Escript.Build.run/1
    (mix) lib/mix/cli.ex:60: Mix.CLI.run_task/2
    (elixir) src/elixir_lexical.erl:17: :elixir_lexical.run/3

λ mix escript.build
Consolidated Jazz.Decoder
Consolidated Jazz.Encoder
Consolidated Access
Consolidated Collectable
Consolidated Enumerable
Consolidated Inspect
Consolidated List.Chars
Consolidated Range.Iterator
Consolidated String.Chars
Consolidated protocols written to _build/dev/consolidated
Generated escript uweb with MIX_ENV=dev

[josevalim]

Simple app that reproduces the issue?

[ericmj]

I had this happen on heroku as well (for hex_web), rerunning the compilation solved it. Race condition?

[josevalim]

Without a way to reproduce... I can't have children.

[alco]

I haven't been able to come up with a minimal example, but I've found a way to reproduce this.

Clone miniweb, add {:jazz, "~> 0.2"} to the list of deps and run mix deps.get once.

Now, every time you run rm -rf _build/dev/lib/jazz; mix compile.protocols you will see the error.

I tried narrowing it down to a dummy project with jazz dependency, but it didn't reproduce there.