From 2d1781f595672a49cb1c873906a68c40862e650b Mon Sep 17 00:00:00 2001
From: David <dlesl@users.noreply.github.com>
Date: Sun, 4 Jul 2021 17:51:25 +0200
Subject: [PATCH 1/2] rebar3Relx: allow `passthru` to be overridden

---
 pkgs/development/beam-modules/rebar3-release.nix | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pkgs/development/beam-modules/rebar3-release.nix b/pkgs/development/beam-modules/rebar3-release.nix
index 98d10cb87c4f..16344f2f194c 100644
--- a/pkgs/development/beam-modules/rebar3-release.nix
+++ b/pkgs/development/beam-modules/rebar3-release.nix
@@ -93,10 +93,10 @@ let
       inherit (erlang.meta) platforms;
     } // meta;
 
-    passthru = {
+    passthru = ({
       packageName = name;
       env = shell self;
-   };
+    } // (if attrs ? passthru then attrs.passthru else {}));
   } // customPhases);
 in
   fix pkg

From ed8502370fc251168eaab03e0a4522e28f364f80 Mon Sep 17 00:00:00 2001
From: David <dlesl@users.noreply.github.com>
Date: Sun, 4 Jul 2021 17:52:19 +0200
Subject: [PATCH 2/2] erlfmt: init at 1.0.0

---
 pkgs/development/beam-modules/default.nix     |  1 +
 .../beam-modules/erlfmt/default.nix           | 20 +++++++++++++++++++
 pkgs/top-level/all-packages.nix               |  2 +-
 3 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 pkgs/development/beam-modules/erlfmt/default.nix

diff --git a/pkgs/development/beam-modules/default.nix b/pkgs/development/beam-modules/default.nix
index 6c33298ff926..6cfa2721bfcd 100644
--- a/pkgs/development/beam-modules/default.nix
+++ b/pkgs/development/beam-modules/default.nix
@@ -38,6 +38,7 @@ let
       mixRelease = callPackage ./mix-release.nix { };
 
       erlang-ls = callPackage ./erlang-ls { };
+      erlfmt = callPackage ./erlfmt { };
 
       # BEAM-based languages.
       elixir = elixir_1_12;
diff --git a/pkgs/development/beam-modules/erlfmt/default.nix b/pkgs/development/beam-modules/erlfmt/default.nix
new file mode 100644
index 000000000000..c903906802e3
--- /dev/null
+++ b/pkgs/development/beam-modules/erlfmt/default.nix
@@ -0,0 +1,20 @@
+{ fetchFromGitHub, rebar3Relx, lib }:
+
+rebar3Relx rec {
+  name = "erlfmt";
+  version = "1.0.0";
+  releaseType = "escript";
+  src = fetchFromGitHub {
+    owner = "WhatsApp";
+    repo = "erlfmt";
+    sha256 = "19apbs9xr4j8qjb3sv9ilknqjw4a7bvp8jvwrjiwvwnxzzm2kjm6";
+    rev = "v${version}";
+  };
+  meta = with lib; {
+    homepage = "https://github.com/WhatsApp/erlfmt";
+    description = "An automated code formatter for Erlang";
+    platforms = platforms.unix;
+    license = licenses.asl20;
+    maintainers = with lib.maintainers; [ dlesl ];
+  };
+}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 18f860ffc514..1985fe852ea8 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -12317,7 +12317,7 @@ in
   erlang_nox = beam_nox.interpreters.erlang;
 
   inherit (beam.packages.erlang)
-    erlang-ls
+    erlang-ls erlfmt
     rebar rebar3 rebar3WithPlugins
     fetchHex beamPackages;