1 files changed, 33 insertions, 16 deletions

diff --git a/src/luarocks/deps.lua b/src/luarocks/deps.lua
index b7d2b236..d9a88c2b 100644
--- a/src/luarocks/deps.lua
+++ b/src/luarocks/deps.lua
@@ -266,13 +266,10 @@ local function get_external_deps_dirs(mode)
    return dirs
 end
 
-local function check_external_dependency_at(extdir, name, ext_files, vars, dirs, err_files)
-   local fs = require("luarocks.fs")
-   local prefix = vars[name.."_DIR"]
-   if not prefix then
-      prefix = extdir
-   end
-   if type(prefix) == "table" then
+local function resolve_prefix(prefix, dirs)
+   if type(prefix) == "string" then
+      return prefix
+   elseif type(prefix) == "table" then
       if prefix.bin then
          dirs.BINDIR.subdir = prefix.bin
       end
@@ -284,8 +281,14 @@ local function check_external_dependency_at(extdir, name, ext_files, vars, dirs,
       if prefix.lib then
          dirs.LIBDIR.subdir = prefix.lib
       end
-      prefix = prefix.prefix
+      return prefix.prefix
    end
+end
+
+local function check_external_dependency_at(prefix, name, ext_files, vars, dirs, err_files, cache)
+   local fs = require("luarocks.fs")
+   cache = cache or {}
+
    for dirname, dirdata in util.sortedpairs(dirs) do
       local paths
       local path_var_value = vars[name.."_"..dirname]
@@ -331,7 +334,10 @@ local function check_external_dependency_at(extdir, name, ext_files, vars, dirs,
 
             for _, d in ipairs(paths) do
                if pattern then
-                  for entry in fs.dir(d) do
+                  if not cache[d] then
+                     cache[d] = fs.list_dir(d)
+                  end
+                  for _, entry in ipairs(cache[d]) do
                      if entry:match(pattern) then
                         found = true
                         break
@@ -366,19 +372,29 @@ local function check_external_dependency_at(extdir, name, ext_files, vars, dirs,
    return true
 end
 
-local function check_external_dependency(name, ext_files, vars, mode)
-   local err_files = {program = {}, header = {}, library = {}}
+local function check_external_dependency(name, ext_files, vars, mode, cache)
+   local ok
    local err_dirname
    local err_testfile
-   for _, extdir in ipairs(cfg.external_deps_dirs) do
-      local dirs = get_external_deps_dirs(mode)
+   local err_files = {program = {}, header = {}, library = {}}
+
+   local dirs = get_external_deps_dirs(mode)
+   
+   local prefixes
+   if vars[name .. "_DIR"] then
+      prefixes = { vars[name .. "_DIR"] }
+   else
+      prefixes = cfg.external_deps_dirs
+   end
+   
+   for _, prefix in ipairs(prefixes) do
+      prefix = resolve_prefix(prefix, dirs)
       if cfg.is_platform("mingw32") and name == "LUA" then
          dirs.LIBDIR.pattern = fun.filter(util.deep_copy(dirs.LIBDIR.pattern), function(s)
             return not s:match("%.a$")
          end)
       end
-      local ok
-      ok, err_dirname, err_testfile = check_external_dependency_at(extdir, name, ext_files, vars, dirs, err_files)
+      ok, err_dirname, err_testfile = check_external_dependency_at(prefix, name, ext_files, vars, dirs, err_files, cache)
       if ok then
          return true
       end
@@ -517,8 +533,9 @@ function deps.check_lua(vars)
    if cfg.luajit_version then
       table.insert(libnames, 1, "luajit-" .. cfg.lua_version)
    end
+   local cache = {}
    for _, libname in ipairs(libnames) do
-      local ok = check_external_dependency("LUA", { library = libname }, vars, "build")
+      local ok = check_external_dependency("LUA", { library = libname }, vars, "build", cache)
       if ok then
          vars.LUALIB = vars.LUA_LIBDIR_FILE
          return true