Fix and reorganize Lua version detection

Make it more robust when detecting the Lua version when working inside a
project, and hopefully make the detection logic easier to track in the
code. Reorganized code so that the `detected` table becomes internal
to the `init_config` operation and only the regular `cfg` global table
is used after that.

Includes regression tests.

3 files changed, 233 insertions, 159 deletions

diff --git a/spec/cmd_spec.lua b/spec/cmd_spec.lua
index 70b9625d..21b25fe5 100644
--- a/spec/cmd_spec.lua
+++ b/spec/cmd_spec.lua
@@ -1,4 +1,5 @@
 local test_env = require("spec.util.test_env")
+local lfs = require("lfs")
 local run = test_env.run
 
 test_env.unload_luarocks()
@@ -31,4 +32,73 @@ describe("LuaRocks command line #integration", function()
       end)
    end)
 
+   describe("--lua-dir", function()
+      it("fails if given an invalid path", function()
+         local output = run.luarocks("--lua-dir=/bad/lua/path")
+         assert.match("Lua interpreter not found at /bad/lua/path", output, 1, true)
+      end)
+
+      it("fails if given a valid path without Lua", function()
+         local output = run.luarocks("--lua-dir=.")
+         assert.match("Lua interpreter not found at .", output, 1, true)
+      end)
+
+      it("passes if given a valid path with Lua", function()
+         assert.truthy(run.luarocks("--lua-dir=" .. test_env.testing_paths.luadir))
+      end)
+   end)
+
+   describe("--lua-version", function()
+      it("warns but continues if given an invalid version", function()
+         local output = run.luarocks("--lua-version=1.0")
+         assert.match("Warning: Could not find a Lua 1.0 interpreter", output, 1, true)
+         assert.match("Lua version: 1.0", output, 1, true)
+      end)
+
+      it("sets the version independently of project tree", function()
+         test_env.run_in_tmp(function(tmpdir)
+            assert.truthy(run.luarocks_bool("init --lua-version=" .. test_env.lua_version .. " --lua-versions=" .. test_env.lua_version))
+
+            local output = run.luarocks("--lua-version=1.0")
+            assert.match("Lua version: 1.0", output, 1, true)
+
+            output = run.luarocks("--lua-version=1.0 --project-tree=.")
+            assert.match("Lua version: 1.0", output, 1, true)
+         end, finally)
+      end)
+   end)
+
+   it("detects version based on project tree", function()
+      test_env.run_in_tmp(function(tmpdir)
+         assert.truthy(run.luarocks_bool("init --lua-version=" .. test_env.lua_version))
+         assert.truthy(run.luarocks_bool("config lua_version 1.0 --project-tree=" .. tmpdir .. "/lua_modules"))
+
+         lfs.mkdir("aaa")
+         lfs.chdir("aaa")
+         lfs.mkdir("bbb")
+         lfs.chdir("bbb")
+
+         local output = run.luarocks("")
+         assert.match("Lua version: 1.0", output, 1, true)
+      end, finally)
+   end)
+
+   -- for backward compatibility
+   it("detects version of a project based on config", function()
+      test_env.run_in_tmp(function(tmpdir)
+         assert.truthy(run.luarocks_bool("init --lua-version=" .. test_env.lua_version))
+         os.remove(".luarocks/config-" .. test_env.lua_version .. ".lua")
+         os.remove(".luarocks/default-lua-version.lua")
+         test_env.write_file(".luarocks/config-5.2.lua", [[ ]], finally)
+
+         lfs.mkdir("aaa")
+         lfs.chdir("aaa")
+         lfs.mkdir("bbb")
+         lfs.chdir("bbb")
+
+         local output = run.luarocks("")
+         assert.match("Lua version: 5.2", output, 1, true)
+      end, finally)
+   end)
+
 end)
diff --git a/src/luarocks/cmd.lua b/src/luarocks/cmd.lua
index bbbdcba1..08505129 100644
--- a/src/luarocks/cmd.lua
+++ b/src/luarocks/cmd.lua
@@ -36,19 +36,6 @@ local function check_popen()
    end
 end
 
-local function check_if_config_is_present(detected, try)
-   local versions = detected.lua_version 
-                    and { detected.lua_version }
-                    or  util.lua_versions("descending")
-   return fun.find(versions, function(v)
-      if util.exists(dir.path(try, ".luarocks", "config-"..v..".lua")) then
-         detected.project_dir = try
-         detected.lua_version = v
-         return detected
-      end
-   end)
-end
-
 local process_tree_flags
 do
    local function replace_tree(flags, root, tree)
@@ -152,32 +139,153 @@ local function process_server_flags(flags)
    return true
 end
 
-local function get_lua_version(flags)
-   if flags["lua-version"] then
-      return flags["lua-version"] 
+local function error_handler(err)
+   local mode = "Arch.: " .. (cfg and cfg.arch or "unknown")
+   if package.config:sub(1, 1) == "\\" then
+      if cfg and cfg.fs_use_modules then
+         mode = mode .. " (fs_use_modules = true)"
+      end
    end
-   local dirs = {}
-   if flags["project-tree"] then
-      table.insert(dirs, dir.path(flags["project-tree"], "..", ".luarocks"))
+   return debug.traceback("LuaRocks "..cfg.program_version..
+      " bug (please report at https://github.com/luarocks/luarocks/issues).\n"..
+      mode.."\n"..err, 2)
+end
+
+--- Display an error message and exit.
+-- @param message string: The error message.
+-- @param exitcode number: the exitcode to use
+local function die(message, exitcode)
+   assert(type(message) == "string", "bad error, expected string, got: " .. type(message))
+   util.printerr("\nError: "..message)
+
+   local ok, err = xpcall(util.run_scheduled_functions, error_handler)
+   if not ok then
+      util.printerr("\nError: "..err)
+      exitcode = cmd.errorcodes.CRASH
    end
-   if cfg.home_tree then
-      table.insert(dirs, dir.path(cfg.home_tree, ".luarocks"))
+
+   os.exit(exitcode or cmd.errorcodes.UNSPECIFIED)
+end
+
+local init_config
+do
+   local detect_config_via_flags
+   do
+      local function find_project_dir(project_tree)
+         if project_tree then
+            return project_tree:gsub("[/\\][^/\\]+$", "")
+         else
+            local try = "."
+            for _ = 1, 10 do -- FIXME detect when root dir was hit instead
+               if util.exists(try .. "/.luarocks") and util.exists(try .. "/lua_modules") then
+                  return try
+               elseif util.exists(try .. "/.luarocks-no-project") then
+                  break
+               end
+               try = try .. "/.."
+            end
+         end
+         return nil
+      end
+   
+      local function find_default_lua_version(flags, project_dir)
+         local dirs = {}
+         if project_dir then
+            table.insert(dirs, dir.path(project_dir, ".luarocks"))
+         end
+         if cfg.home_tree then
+            table.insert(dirs, dir.path(cfg.home_tree, ".luarocks"))
+         end
+         table.insert(dirs, cfg.sysconfdir)
+         for _, d in ipairs(dirs) do
+            local f = dir.path(d, "default-lua-version.lua")
+            local mod, err = loadfile(f, "t")
+            if mod then
+               local pok, ver = pcall(mod)
+               if pok and type(ver) == "string" and ver:match("%d+.%d+") then
+                  if flags["verbose"] then
+                     util.printout("Defaulting to Lua " .. ver .. " based on " .. f .. " ...")
+                  end
+                  return ver
+               end
+            end
+         end
+         return nil
+      end
+   
+      local function find_version_from_config(dirname)
+         return fun.find(util.lua_versions("descending"), function(v)
+            if util.exists(dir.path(dirname, ".luarocks", "config-"..v..".lua")) then
+               return v
+            end
+         end)
+      end
+   
+      local function detect_lua_via_flags(flags, project_dir)
+         local lua_version = flags["lua-version"]
+                             or find_default_lua_version(flags, project_dir)
+                             or (project_dir and find_version_from_config(project_dir))
+      
+         if flags["lua-dir"] then
+            local detected, err = util.find_lua(flags["lua-dir"], lua_version)
+            if not detected then
+               die(err)
+            end
+            return detected
+         end
+      
+         if lua_version then
+            local path_sep = (package.config:sub(1, 1) == "\\" and ";" or ":")
+            for bindir in os.getenv("PATH"):gmatch("[^"..path_sep.."]+") do
+               local parentdir = bindir:gsub("[\\/][^\\/]+[\\/]?$", "")
+               local detected = util.find_lua(dir.path(parentdir), lua_version)
+               if detected then
+                  return detected
+               end
+               detected = util.find_lua(bindir, lua_version)
+               if detected then
+                  return detected
+               end
+            end
+            return {
+               lua_version = lua_version,
+            }
+         end
+         
+         return {}
+      end
+      
+      detect_config_via_flags = function(flags)
+         local project_dir = find_project_dir(flags["project-tree"])
+         local detected = detect_lua_via_flags(flags, project_dir)
+         detected.project_dir = project_dir
+         return detected
+      end
    end
-   table.insert(dirs, cfg.sysconfdir)
-   for _, d in ipairs(dirs) do
-      local f = dir.path(d, "default-lua-version.lua")
-      local mod, err = loadfile(f, "t")
-      if mod then
-         local pok, ver = pcall(mod)
-         if pok and type(ver) == "string" and ver:match("%d+.%d+") then
-            if flags["verbose"] then
-               util.printout("Defaulting to Lua " .. ver .. " based on " .. f .. " ...")
+   
+   init_config = function(flags)
+      local detected = detect_config_via_flags(flags)
+   
+      -- FIXME A quick hack for the experimental Windows build
+      if os.getenv("LUAROCKS_CROSS_COMPILING") then
+         cfg.each_platform = function()
+            local i = 0
+            local plats = { "unix", "linux" }
+            return function()
+               i = i + 1
+               return plats[i]
             end
-            return ver
          end
+         fs.init()
+      end
+   
+      local ok, err = cfg.init(detected, util.warning)
+      if not ok then
+         return nil, err
       end
+      
+      return (detected.lua_dir ~= nil)
    end
-   return nil
 end
 
 --- Main command-line processor.
@@ -192,34 +300,6 @@ function cmd.run_command(description, commands, external_namespace, ...)
 
    check_popen()
 
-   local function error_handler(err)
-      local mode = "Arch.: " .. (cfg and cfg.arch or "unknown")
-      if package.config:sub(1, 1) == "\\" then
-         if cfg and cfg.fs_use_modules then
-            mode = mode .. " (fs_use_modules = true)"
-         end
-      end
-      return debug.traceback("LuaRocks "..cfg.program_version..
-         " bug (please report at https://github.com/luarocks/luarocks/issues).\n"..
-         mode.."\n"..err, 2)
-   end
-
-   --- Display an error message and exit.
-   -- @param message string: The error message.
-   -- @param exitcode number: the exitcode to use
-   local function die(message, exitcode)
-      assert(type(message) == "string", "bad error, expected string, got: " .. type(message))
-      util.printerr("\nError: "..message)
-
-      local ok, err = xpcall(util.run_scheduled_functions, error_handler)
-      if not ok then
-         util.printerr("\nError: "..err)
-         exitcode = cmd.errorcodes.CRASH
-      end
-
-      os.exit(exitcode or cmd.errorcodes.UNSPECIFIED)
-   end
-
    local function process_arguments(...)
       local args = {...}
       local cmdline_vars = {}
@@ -285,122 +365,44 @@ function cmd.run_command(description, commands, external_namespace, ...)
       end
    end
 
-   local lua_version = get_lua_version(flags)
-
    if flags["deps-mode"] and not deps.check_deps_mode_flag(flags["deps-mode"]) then
       die("Invalid entry for --deps-mode.")
    end
    
-   local lua_found = false
-
-   local detected
-   if flags["lua-dir"] then
-      local err
-      detected, err = util.find_lua(flags["lua-dir"], lua_version)
-      if not detected then
-         die(err)
-      end
-      lua_found = true
-      assert(detected.lua_version)
-      assert(detected.lua_dir)
-   elseif lua_version then
-      local path_sep = (package.config:sub(1, 1) == "\\" and ";" or ":")
-      for bindir in os.getenv("PATH"):gmatch("[^"..path_sep.."]+") do
-         local parentdir = bindir:gsub("[\\/][^\\/]+[\\/]?$", "")
-         detected = util.find_lua(dir.path(parentdir), lua_version)
-         if detected then
-            break
-         end
-         detected = util.find_lua(bindir, lua_version)
-         if detected then
-            break
-         end
-      end
-      if detected then
-         lua_found = true
-      else
-         detected = {
-            lua_version = lua_version,
-         }
-      end
-   end
-
-   if flags["project-tree"] then
-      local project_tree = flags["project-tree"]:gsub("[/\\][^/\\]+$", "")
-      detected = detected or {}
-      detected.project_dir = project_tree
-      local d = check_if_config_is_present(detected, project_tree)
-      if d then
-         detected = d
-      end
-   else
-      detected = detected or {}
-      local try = "."
-      for _ = 1, 10 do -- FIXME detect when root dir was hit instead
-         if util.exists(try .. "/.luarocks") and util.exists(try .. "/lua_modules") then
-            local d = check_if_config_is_present(detected, try)
-            if d then
-               detected = d
-               break
-            end
-         elseif util.exists(try .. "/.luarocks-no-project") then
-            break
-         end
-         try = try .. "/.."
-      end
-   end
-
-   -- FIXME A quick hack for the experimental Windows build
-   if os.getenv("LUAROCKS_CROSS_COMPILING") then
-      cfg.each_platform = function()
-         local i = 0
-         local plats = { "unix", "linux" }
-         return function()
-            i = i + 1
-            return plats[i]
-         end
-      end
-      fs.init()
-   end
-
    -----------------------------------------------------------------------------
-   local ok, err = cfg.init(detected, util.warning)
-   if not ok then
+   local lua_found, err = init_config(flags)
+   if err then
       die(err)
    end
    -----------------------------------------------------------------------------
 
-   fs.init()
+   if flags["version"] then
+      util.printout(program.." "..cfg.program_version)
+      util.printout(description)
+      util.printout()
+      os.exit(cmd.errorcodes.OK)
+   end
 
-   lua_version = cfg.lua_version
+   fs.init()
 
+   -- if the Lua interpreter wasn't explicitly found before cfg.init,
+   -- try again now.
    if not lua_found then
       if cfg.variables.LUA_DIR then
-         local found = util.find_lua(cfg.variables.LUA_DIR, cfg.lua_version)
-         if found then
-            lua_found = true
-         end
+         lua_found = util.find_lua(cfg.variables.LUA_DIR, cfg.lua_version)
       end
    end
 
    if not lua_found then
-      util.warning("Could not find a Lua interpreter for version " ..
-                   lua_version .. " in your PATH. " ..
+      util.warning("Could not find a Lua " .. cfg.lua_version .. " interpreter in your PATH. " ..
                    "Modules may not install with the correct configurations. " ..
                    "You may want to specify to the path prefix to your build " ..
-                   "of Lua " .. lua_version .. " using --lua-dir")
+                   "of Lua " .. cfg.lua_version .. " using --lua-dir")
    end
    cfg.lua_found = lua_found
 
-   if detected.project_dir then
-      detected.project_dir = fs.absolute_name(detected.project_dir)
-   end
-
-   if flags["version"] then
-      util.printout(program.." "..cfg.program_version)
-      util.printout(description)
-      util.printout()
-      os.exit(cmd.errorcodes.OK)
+   if cfg.project_dir then
+      cfg.project_dir = fs.absolute_name(cfg.project_dir)
    end
 
    for _, module_name in ipairs(fs.modules(external_namespace)) do
@@ -418,7 +420,7 @@ function cmd.run_command(description, commands, external_namespace, ...)
       die("Current directory does not exist. Please run LuaRocks from an existing directory.")
    end
 
-   ok, err = process_tree_flags(flags, detected.project_dir)
+   ok, err = process_tree_flags(flags, cfg.project_dir)
    if not ok then
       die(err)
    end
diff --git a/src/luarocks/core/cfg.lua b/src/luarocks/core/cfg.lua
index 02fb564b..d8442962 100644
--- a/src/luarocks/core/cfg.lua
+++ b/src/luarocks/core/cfg.lua
@@ -561,6 +561,7 @@ function cfg.init(detected, warning)
    local lua_incdir = detected.lua_incdir or hardcoded.LUA_INCDIR
    local lua_libdir = detected.lua_libdir or hardcoded.LUA_LIBDIR
    local lua_dir = detected.lua_dir or hardcoded.LUA_DIR or (lua_bindir and lua_bindir:gsub("[\\/]bin$", ""))
+   local project_dir = detected.project_dir
    
    local init = cfg.init
 
@@ -636,8 +637,8 @@ function cfg.init(detected, warning)
       local name = "config-"..cfg.lua_version..".lua"
       sys_config_file = (cfg.sysconfdir .. "/" .. name):gsub("\\", "/")
       home_config_file = (cfg.homeconfdir .. "/" .. name):gsub("\\", "/")
-      if detected.project_dir then
-         project_config_file = detected.project_dir .. "/.luarocks/" .. name
+      if project_dir then
+         project_config_file = project_dir .. "/.luarocks/" .. name
       end
    end
 
@@ -680,7 +681,7 @@ function cfg.init(detected, warning)
       end
 
       -- finally, use the project-specific config file if any
-      if detected.project_dir then
+      if project_dir then
          project_config_ok, err = load_config_file(cfg, platforms, project_config_file)
          if err then
             return nil, err, "config"
@@ -694,6 +695,7 @@ function cfg.init(detected, warning)
    ----------------------------------------
 
    -- Settings detected or given via the CLI (i.e. --lua-dir) take precedence over config files:
+   cfg.project_dir = detected.project_dir
    cfg.lua_version = detected.lua_version or cfg.lua_version
    cfg.luajit_version = detected.luajit_version or cfg.luajit_version
    cfg.lua_interpreter = detected.lua_interpreter or cfg.lua_interpreter
@@ -731,7 +733,7 @@ function cfg.init(detected, warning)
    cfg.user_agent = "LuaRocks/"..cfg.program_version.." "..cfg.arch
 
    cfg.config_files = {
-      project = detected.project_dir and {
+      project = project_dir and {
          file = project_config_file,
          found = not not project_config_ok,
       },