Compilation doesn't fail for warning: function/x is undefined(module is not available or is yet to be defined) with --warnings-as-errors as enabled

[bagarey]

Environment

• Elixir & Erlang/OTP versions (elixir --version):

Erlang/OTP 22 [erts-10.7.2.4] [source] [64-bit] [smp:48:48] [ds:48:48:10] [async-threads:1]
Interactive Elixir (1.10.4) - press Ctrl+C to exit (type h() ENTER for help)

• Operating system: Red Hat Enterprise Linux 7.5

Current behavior

• An umbrella application with app common and sim are created and compiled successfully
• Add calling of Sim.hello in Common.hello function
• Compiling from umbrella root

$ mix compile --warnings-as-errors
==> common
Compiling 1 file (.ex)
warning: Sim.hello/0 is undefined (module Sim is not available or is yet to be defined)
  lib/common.ex:17: Common.hello/0

Generated common app
==> sim
Compiling 1 file (.ex)
Generated sim app

$ echo $?
0

Compiling the app in standalone doesn't fail either

[common]$ mix compile --warnings-as-errors
Compiling 1 file (.ex)
warning: Sim.hello/0 is undefined (module Sim is not available or is yet to be defined)
  lib/common.ex:17: Common.hello/0

Generated common app

[common]$ echo $?
0

Expected behavior

The compiler should've failed similar to when an unused function is used.

$ mix compile --warnings-as-errors
==> common
Compiling 1 file (.ex)
warning: function foo/0 is unused
  lib/common.ex:20

warning: Sim.hello/0 is undefined (module Sim is not available or is yet to be defined)
  lib/common.ex:17: Common.hello/0

Compilation failed due to warnings while using the --warnings-as-errors option

$ echo $?
1

[josevalim]

I believe this is fixed in Elixir latest. I will double check when I am at the computer. :)

[josevalim]

Yup, fixed on more recent Elixir versions. :)

[bagarey]

@josevalim: Thank you for confirming this.