LS Crashes when loading formatter configuration

[lukaszsamson]

Environment

• Elixir & Erlang versions (elixir --version):
  Erlang/OTP 22 [erts-10.7.2.1] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe]
  Elixir 1.10.4 (compiled with Erlang/OTP 22)
• Operating system: macos
• Editor or IDE name (e.g. Emacs/VSCode): 0.5
• LSP Client name: vscode-elixir-ls
  When opening an umbrella apps I noticed some non deterministic crashes.

Started ElixirLS v0.5.0
Elixir version: "1.10.4 (compiled with Erlang/OTP 22)"
Erlang version: "22"
ElixirLS compiled with Elixir 1.10.4 and erlang 22
MIX_ENV: dev
MIX_TARGET: 

==> phoenix
Compiling 66 files (.ex)
Generated phoenix app

==> backoffice
Compiling 86 files (.ex)
Generated backoffice app
[Info  - 11:38:52 AM] Compile took 94721 milliseconds
[Info  - 11:38:52 AM] [ElixirLS WorkspaceSymbols] Indexing...
MIX_ENV: dev
MIX_TARGET: 


11:38:54.836 [error] GenServer ElixirLS.LanguageServer.Server terminating
** (Mix.Error) Unknown dependency :phoenix given to :import_deps in the formatter configuration. The dependency is not listed in your mix.exs for environment :dev
    (mix 1.10.4) lib/mix.ex:392: Mix.raise/1
    (mix 1.10.4) lib/mix/tasks/format.ex:246: anonymous fn/3 in Mix.Tasks.Format.eval_deps_opts/2
    (elixir 1.10.4) lib/enum.ex:2111: Enum."-reduce/3-lists^foldl/2-0-"/3
    (mix 1.10.4) lib/mix/tasks/format.ex:245: Mix.Tasks.Format.eval_deps_opts/2
    (mix 1.10.4) lib/mix/tasks/format.ex:201: anonymous fn/5 in Mix.Tasks.Format.eval_deps_and_subdirectories/4
    (mix 1.10.4) lib/mix/tasks/format.ex:276: anonymous fn/2 in Mix.Tasks.Format.eval_subs_opts/3
    (elixir 1.10.4) lib/enum.ex:1094: anonymous fn/3 in Enum.flat_map_reduce/3
    (elixir 1.10.4) lib/enum.ex:3686: Enumerable.List.reduce/3

Fallback message for "go to location"
vscode 1.47

11:38:52.927 [error] GenServer ElixirLS.LanguageServer.Server terminating
** (Mix.Error) Unknown dependency :phoenix given to :import_deps in the formatter configuration. The dependency is not listed in your mix.exs for environment :dev
    (mix 1.10.4) lib/mix.ex:392: Mix.raise/1
    (mix 1.10.4) lib/mix/tasks/format.ex:246: anonymous fn/3 in Mix.Tasks.Format.eval_deps_opts/2
    (elixir 1.10.4) lib/enum.ex:2111: Enum."-reduce/3-lists^foldl/2-0-"/3
    (mix 1.10.4) lib/mix/tasks/format.ex:245: Mix.Tasks.Format.eval_deps_opts/2
    (mix 1.10.4) lib/mix/tasks/format.ex:201: anonymous fn/5 in Mix.Tasks.Format.eval_deps_and_subdirectories/4
    (mix 1.10.4) lib/mix/tasks/format.ex:276: anonymous fn/2 in Mix.Tasks.Format.eval_subs_opts/3
    (elixir 1.10.4) lib/enum.ex:1094: anonymous fn/3 in Enum.flat_map_reduce/3
    (elixir 1.10.4) lib/enum.ex:3686: Enumerable.List.reduce/3
    (elixir 1.10.4) lib/enum.ex:1093: Enum.flat_map_reduce/3
    (mix 1.10.4) lib/mix/tasks/format.ex:200: anonymous fn/5 in Mix.Tasks.Format.eval_deps_and_subdirectories/4
    (mix 1.10.4) lib/mix/tasks/format.ex:160: Mix.Tasks.Format.formatter_opts_for_file/2
    (language_server 0.5.0) lib/language_server/server.ex:487: ElixirLS.LanguageServer.Server.handle_request/2
    (language_server 0.5.0) lib/language_server/server.ex:332: ElixirLS.LanguageServer.Server.handle_request_packet/3
    (language_server 0.5.0) lib/language_server/server.ex:126: ElixirLS.LanguageServer.Server.handle_cast/2
    (stdlib 3.12.1) gen_server.erl:637: :gen_server.try_dispatch/4
    (stdlib 3.12.1) gen_server.erl:711: :gen_server.handle_msg/6
    (stdlib 3.12.1) proc_lib.erl:249: :proc_lib.init_p_do_apply/3

16:09:41.897 [error] GenServer ElixirLS.LanguageServer.Server terminating
** (Mix.Error) Unknown dependency :ecto given to :import_deps in the formatter configuration. The dependency is not listed in your mix.exs for environment :dev
    (mix 1.10.4) lib/mix.ex:392: Mix.raise/1
    (mix 1.10.4) lib/mix/tasks/format.ex:246: anonymous fn/3 in Mix.Tasks.Format.eval_deps_opts/2
    (elixir 1.10.4) lib/enum.ex:2111: Enum."-reduce/3-lists^foldl/2-0-"/3
    (mix 1.10.4) lib/mix/tasks/format.ex:245: Mix.Tasks.Format.eval_deps_opts/2
    (mix 1.10.4) lib/mix/tasks/format.ex:201: anonymous fn/5 in Mix.Tasks.Format.eval_deps_and_subdirectories/4
    (mix 1.10.4) lib/mix/tasks/format.ex:210: Mix.Tasks.Format.maybe_cache_in_manifest/3
    (mix 1.10.4) lib/mix/tasks/format.ex:160: Mix.Tasks.Format.formatter_opts_for_file/2
    (language_server 0.5.0) lib/language_server/server.ex:487: ElixirLS.LanguageServer.Server.handle_request/2
    (language_server 0.5.0) lib/language_server/server.ex:332: ElixirLS.LanguageServer.Server.handle_request_packet/3
    (language_server 0.5.0) lib/language_server/server.ex:126: ElixirLS.LanguageServer.Server.handle_cast/2
    (stdlib 3.12.1) gen_server.erl:637: :gen_server.try_dispatch/4
    (stdlib 3.12.1) gen_server.erl:711: :gen_server.handle_msg/6
    (stdlib 3.12.1) proc_lib.erl:249: :proc_lib.init_p_do_apply/3

:phoenix and :ecto are definitely in the deps (of all the apps in the umbrella) and the deps are fetched. It seems that there is a race condition and under some circumstances the formatter config cannot be fetched.