2 files changed, 37 insertions, 6 deletions

diff --git a/src/luarocks/build.lua b/src/luarocks/build.lua
index e545d390..d5c474ca 100644
--- a/src/luarocks/build.lua
+++ b/src/luarocks/build.lua
@@ -129,7 +129,37 @@ local function process_dependencies(rockspec, opts)
 
    if not opts.build_only_deps then
       if next(rockspec.build_dependencies) then
+
+         local user_lua_version = cfg.lua_version
+         local running_lua_version = _VERSION:sub(5)
+
+         if running_lua_version ~= user_lua_version then
+            -- Temporarily flip the user-selected Lua version,
+            -- so that we install build dependencies for the
+            -- Lua version on which the LuaRocks program is running.
+
+            -- HACK: we have to do this by flipping a bunch of
+            -- global config settings, and this list may not be complete.
+            cfg.lua_version = running_lua_version
+            cfg.lua_modules_path = cfg.lua_modules_path:gsub(user_lua_version:gsub("%.", "%%."), running_lua_version)
+            cfg.lib_modules_path = cfg.lib_modules_path:gsub(user_lua_version:gsub("%.", "%%."), running_lua_version)
+            cfg.rocks_subdir = cfg.rocks_subdir:gsub(user_lua_version:gsub("%.", "%%."), running_lua_version)
+            path.use_tree(cfg.root_dir)
+         end
+
          local ok, err, errcode = deps.fulfill_dependencies(rockspec, "build_dependencies", "all", opts.verify)
+
+         path.add_to_package_paths(cfg.root_dir)
+
+         if running_lua_version ~= user_lua_version then
+            -- flip the settings back
+            cfg.lua_version = user_lua_version
+            cfg.lua_modules_path = cfg.lua_modules_path:gsub(running_lua_version:gsub("%.", "%%."), user_lua_version)
+            cfg.lib_modules_path = cfg.lib_modules_path:gsub(running_lua_version:gsub("%.", "%%."), user_lua_version)
+            cfg.rocks_subdir = cfg.rocks_subdir:gsub(running_lua_version:gsub("%.", "%%."), user_lua_version)
+            path.use_tree(cfg.root_dir)
+         end
+
          if err then
             return nil, err, errcode
          end
diff --git a/src/luarocks/path.lua b/src/luarocks/path.lua
index a9f04ef0..19657c83 100644
--- a/src/luarocks/path.lua
+++ b/src/luarocks/path.lua
@@ -219,13 +219,14 @@ function path.use_tree(tree)
    cfg.deploy_bin_dir = path.deploy_bin_dir(tree)
    cfg.deploy_lua_dir = path.deploy_lua_dir(tree)
    cfg.deploy_lib_dir = path.deploy_lib_dir(tree)
+end
 
-   -- TODO Do we want LuaRocks itself to use whatever tree is in use?
-   -- package.path = dir.path(path.deploy_lua_dir(tree), "?.lua") .. ";"
-   --             .. dir.path(path.deploy_lua_dir(tree), "?/init.lua") .. ";"
-   --             .. package.path
-   -- package.cpath = dir.path(path.deploy_lib_dir(tree), "?." .. cfg.lib_extension) .. ";"
-   --              .. package.cpath
+function path.add_to_package_paths(tree)
+   package.path = dir.path(path.deploy_lua_dir(tree), "?.lua") .. ";"
+               .. dir.path(path.deploy_lua_dir(tree), "?/init.lua") .. ";"
+               .. package.path
+   package.cpath = dir.path(path.deploy_lib_dir(tree), "?." .. cfg.lib_extension) .. ";"
+                .. package.cpath
 end
 
 --- Get the namespace of a locally-installed rock, if any.