Add support for rebar3 plugins to buildHex.

Allow specifying pluginDeps for buildHex listing rebar3 plugins which
are required for given package to be built by rebar3.

pkgs/development/erlang-modules/build-hex.nix

@@ -2,7 +2,7 @@
 
 { name, version, sha256
 , hexPkg ? name
-, buildInputs ? [], erlangDeps ? []
+, buildInputs ? [], erlangDeps ? [], pluginDeps ? []
 , postPatch ? ""
 , compilePorts ? false
 , ... }@attrs:
@@ -39,14 +39,22 @@ stdenv.mkDerivation (attrs // {
     recursiveDeps = uniqList {
        inputList = flatten (map getDeps erlangDeps);
     };
+    recursivePluginsDeps = uniqList {
+       inputList = flatten (map getDeps pluginDeps);
+    };
   in ''
     runHook preConfigure
-    mkdir -p _build/default/lib/
+    mkdir -p _build/default/{lib,plugins}/
     ${concatMapStrings (dep: ''
       header "linking erlang dependency ${dep}"
       ln -s "${dep}" "_build/default/lib/${dep.packageName}"
       stopNest
     '') recursiveDeps}
+    ${concatMapStrings (dep: ''
+      header "linking rebar3 plugins ${dep}"
+      ln -s "${dep}" "_build/default/plugins/${dep.packageName}"
+      stopNest
+    '') recursivePluginsDeps}
     runHook postConfigure
   '';
 
@@ -55,7 +63,9 @@ stdenv.mkDerivation (attrs // {
   buildPhase = ''
     runHook preBuild
     HOME=. rebar3 do update, compile
+    ${if compilePorts then ''
     HOME=. rebar3 pc compile
+    '' else ''''}
     runHook postBuild
   '';
 

pkgs/development/erlang-modules/default.nix

@@ -7,6 +7,7 @@ let
     buildErlang = callPackage ./build-erlang.nix {};
     buildHex = callPackage ./build-hex.nix {};
 
+    rebar3-pc = callPackage ./hex/rebar3-pc.nix {};
     esqlite = callPackage ./hex/esqlite.nix {};
     goldrush = callPackage ./hex/goldrush.nix {};
     ibrowse = callPackage ./hex/ibrowse.nix {};

pkgs/development/erlang-modules/hex/esqlite.nix

@@ -1,8 +1,9 @@
-{ buildHex }:
+{ buildHex, rebar3-pc }:
 
 buildHex {
   name = "esqlite";
   version = "0.2.1";
   sha256 = "1296fn1lz4lz4zqzn4dwc3flgkh0i6n4sydg501faabfbv8d3wkr";
   compilePorts = true;
+  pluginDeps = [ rebar3-pc ];
 }

pkgs/development/erlang-modules/hex/rebar3-pc.nix

@@ -0,0 +1,7 @@
+{ buildHex, goldrush }:
+
+buildHex {
+  name = "pc";
+  version = "1.1.0";
+  sha256 = "1br5xfl4b2z70b6a2ccxppn64jvkqgpmy4y9v81kxzb91z0ss9ma";
+}