buildLuarocksPackage: Several improvements

Summary of main changes:
- Now makes use of luarocks dependency resolution (builds will fail if
  rockspec dependencies are unmet)
- Renamed argument `external_deps` -> `exernalDeps` and add
  functionality to handle external dependencies that are multiple-output
  derivations
- Added an `extraVariables` argument for appending to the contents of
  luarocks config `variables` table
- The `rockspecFilename` argument default is now actually used
- The `disabled` argument can now be overriden with a less-restrictive
  check, as it now just sets `meta.broken` instead of throwing an error
  during eval
- The `doCheck` argument is now actually honored if set to `true`

pkgs/development/interpreters/lua-5/build-lua-package.nix

@@ -28,12 +28,13 @@ name ? "${attrs.pname}-${attrs.version}"
 , propagatedNativeBuildInputs ? []
 
 # used to disable derivation, useful for specific lua versions
+# TODO move from this setting meta.broken to a 'disabled' attribute on the
+# package, then use that to skip/include in each lua${ver}Packages set?
 , disabled ? false
 
 # Additional arguments to pass to the makeWrapper function, which wraps
 # generated binaries.
 , makeWrapperArgs ? []
-, external_deps ? propagatedBuildInputs ++ buildInputs
 
 # Skip wrapping of lua programs altogether
 , dontWrapLuaPrograms ? false
@@ -43,11 +44,19 @@ name ? "${attrs.pname}-${attrs.version}"
 , passthru ? {}
 , doCheck ? false
 
-# appended to the luarocks generated config
-# in peculiar variables like { EVENT_INCDIR } can be useful to work around
-# luarocks limitations, ie, luarocks consider include/lib folders to be subfolders of the same package in external_deps_dirs
-# as explained in https://github.com/luarocks/luarocks/issues/766
+# Non-Lua / system (e.g. C library) dependencies. Is a list of deps, where
+# each dep is either a derivation, or an attribute set like
+# { name = "rockspec external_dependencies key"; dep = derivation; }
+# The latter is used to work-around luarocks having a problem with
+# multiple-output derivations as external deps:
+# https://github.com/luarocks/luarocks/issues/766<Paste>
+, externalDeps ? lib.unique (lib.filter (drv: !drv ? luaModule) (propagatedBuildInputs ++ buildInputs))
+
+# Appended to the generated luarocks config
 , extraConfig ? ""
+# Inserted into the generated luarocks config in the "variables" table
+, extraVariables ? ""
+# The two above arguments have access to builder variables -- e.g. to $out
 
 # relative to srcRoot, path to the rockspec to use when using rocks
 , rockspecFilename ?  "../*.rockspec"
@@ -59,44 +68,95 @@ name ? "${attrs.pname}-${attrs.version}"
 
 
 # Keep extra attributes from `attrs`, e.g., `patchPhase', etc.
-if disabled
-then throw "${name} not supported for interpreter ${lua}"
-else
 
 let
-
-  deps_dirs= lib.concatStringsSep ", " (
-    map (x: "\"${builtins.toString x}\"") external_deps
-  );
-
-  # TODO
-  # - add rocktrees (look at torch-distro.nix/https://github.com/luarocks/luarocks/wiki/Config-file-format)
-  # - silence warnings
-  luarocks_config = "luarocksConfig";
+  # TODO fix warnings "Couldn't load rockspec for ..." during manifest
+  # construction -- from initial investigation, appears it will require
+  # upstream luarocks changes to fix cleanly (during manifest construction,
+  # luarocks only looks for rockspecs in the default/system tree instead of all
+  # configured trees)
+  luarocks_config = "luarocks-config.lua";
   luarocks_content = ''
     local_cache = ""
-    -- array of strings
-    external_deps_dirs = {
-    ${deps_dirs}
-    }
+    -- To prevent collisions when creating environments, we install the rock
+    -- files into per-package subdirectories
+    rocks_subdir = '${rocksSubdir}'
+    -- Then we need to tell luarocks where to find the rock files per
+    -- dependency
     rocks_trees = {
+      ${lib.concatStringsSep "\n, " rocksTrees}
+    }
+  '' + lib.optionalString lua.pkgs.isLuaJIT ''
+    -- Luajit provides some additional functionality built-in; this exposes
+    -- that to luarock's dependency system
+    rocks_provided = {
+      jit='${lua.luaversion}-1';
+      ffi='${lua.luaversion}-1';
+      luaffi='${lua.luaversion}-1';
+      bit='${lua.luaversion}-1';
+    }
+  '' + ''
+    -- For single-output external dependencies
+    external_deps_dirs = {
+      ${lib.concatStringsSep "\n, " externalDepsDirs}
+    }
+    variables = {
+      -- Some needed machinery to handle multiple-output external dependencies,
+      -- as per https://github.com/luarocks/luarocks/issues/766
+      ${lib.optionalString (lib.length depVariables > 0) ''
+      ${lib.concatStringsSep "\n  " depVariables}''}
+      ${extraVariables}
     }
     ${extraConfig}
   '';
+
+  rocksSubdir = "${attrs.pname}-${version}-rocks";
+
+  externalDepsDirs = map
+    (x: "'${builtins.toString x}'")
+    (lib.filter (lib.isDerivation) externalDeps);
+
+  rocksTrees = lib.imap0
+    (i: dep: "{ name = [[dep-${toString i}]], root = '${dep}', rocks_dir = '${dep}/${dep.rocksSubdir}' }")
+    requiredLuaRocks;
+
+  # Filter out the lua derivation itself from the Lua module dependency
+  # closure, as it doesn't have a rock tree :)
+  requiredLuaRocks = lib.filter (d: d ? luaModule)
+    (lua.pkgs.requiredLuaModules propagatedBuildInputs);
+
+  # Explicitly point luarocks to the relevant locations for multiple-output
+  # derivations that are external dependencies, to work around an issue it has
+  # (https://github.com/luarocks/luarocks/issues/766)
+  depVariables = lib.concatMap ({name, dep}: [
+    "${name}_INCDIR='${lib.getDev dep}/include';"
+    "${name}_LIBDIR='${lib.getLib dep}/lib';"
+    "${name}_BINDIR='${lib.getBin dep}/bin';"
+  ]) externalDeps';
+
+  # example externalDeps': [ { name = "CRYPTO"; dep = pkgs.openssl; } ]
+  externalDeps' = lib.filter (dep: !lib.isDerivation dep) externalDeps;
 in
 toLuaModule ( lua.stdenv.mkDerivation (
-builtins.removeAttrs attrs ["disabled" "checkInputs"] // {
+builtins.removeAttrs attrs ["disabled" "checkInputs" "externalDeps"] // {
 
   name = namePrefix + name;
 
   buildInputs = [ wrapLua lua.pkgs.luarocks ]
     ++ buildInputs
     ++ lib.optionals doCheck checkInputs
+    ++ (map (d: d.dep) externalDeps')
     ;
 
   # propagate lua to active setup-hook in nix-shell
   propagatedBuildInputs = propagatedBuildInputs ++ [ lua ];
-  doCheck = false;
+  inherit doCheck;
+
+  # @-patterns do not capture formal argument default values, so we need to
+  # explicitly inherit this for it to be available as a shell variable in the
+  # builder
+  inherit rockspecFilename;
+  inherit rocksSubdir;
 
   # enabled only for src.rock
   setSourceRoot= let
@@ -163,23 +223,20 @@ builtins.removeAttrs attrs ["disabled" "checkInputs"] // {
 
     nix_debug "ROCKSPEC $rockspecFilename"
     nix_debug "cwd: $PWD"
-    $LUAROCKS make --deps-mode=none --tree $out ''${rockspecFilename}
-
-    # to prevent collisions when creating environments
-    # also added -f as it doesn't always exist
-    # don't remove the whole directory as
-    rm -rf $out/lib/luarocks/rocks-${lua.luaversion}/manifest
+    $LUAROCKS make --deps-mode=all --tree=$out ''${rockspecFilename}
 
     runHook postInstall
   '';
 
   passthru = {
     inherit lua; # The lua interpreter
+    inherit externalDeps;
   } // passthru;
 
   meta = with lib.maintainers; {
     platforms = lua.meta.platforms;
     # add extra maintainer(s) to every package
     maintainers = (meta.maintainers or []) ++ [ ];
+    broken = disabled;
   } // meta;
 }))