loader.which: new option for searching package.path and cpath

Adds a new second argument, `where`, a string which indicates places
to search for the module.

If `where` contains "l", it will search using the LuaRocks loader; if it
contains "p", it will look in the filesystem using package.path and
package.cpath. You can use both at the same time.

If successful, it will return four values.

* If found using the LuaRocks loader, it will return:
   * filename of the module (eg. "/usr/local/lib/lua/5.1/socket/core.so"),
   * rock name
   * rock version
   * "l" to indicate the match comes from the loader.

* If found scanning package.path and package.cpath, it will return:
   * filename of the module (eg. "/usr/local/lib/lua/5.1/socket/core.so"),
   * "path" or "cpath"
   * nil
   * "p" to indicate the match comes from scanning package.path and cpath.

If unsuccessful, nothing is returned.

3 files changed, 66 insertions, 27 deletions

diff --git a/spec/loader_spec.lua b/spec/loader_spec.lua
index 35179080..c8526117 100644
--- a/spec/loader_spec.lua
+++ b/spec/loader_spec.lua
@@ -4,10 +4,21 @@ local testing_paths = test_env.testing_paths
 local write_file = test_env.write_file
 
 describe("luarocks.loader", function()
+
+   before_each(function()
+      test_env.setup_specs()
+   end)
+
    describe("#unit", function()
       it("starts", function()
          assert(run.lua_bool([[-e "require 'luarocks.loader'; print(package.loaded['luarocks.loaded'])"]]))
       end)
+
+      describe("which", function()
+         it("finds modules using package.path", function()
+            assert(run.lua_bool([[-e "loader = require 'luarocks.loader'; local x,y,z,p = loader.which('luarocks.loader', 'p'); assert(p == 'p')"]]))
+         end)
+      end)
    end)
 
    describe("#integration", function()
@@ -21,13 +32,13 @@ describe("luarocks.loader", function()
                   url = "file://]] .. tmpdir:gsub("\\", "/") .. [[/rock_b_01.lua"
                }
                build = {
-                  type = "builtin", 
+                  type = "builtin",
                   modules = {
                      rock_b = "rock_b_01.lua"
                   }
                }
             ]], finally)
-   
+
             write_file("rock_b_10.lua", "print('ROCK B 1.0'); return {}", finally)
             write_file("rock_b-1.0-1.rockspec", [[
                package = "rock_b"
@@ -36,13 +47,13 @@ describe("luarocks.loader", function()
                   url = "file://]] .. tmpdir:gsub("\\", "/") .. [[/rock_b_10.lua"
                }
                build = {
-                  type = "builtin", 
+                  type = "builtin",
                   modules = {
                      rock_b = "rock_b_10.lua"
                   }
                }
             ]], finally)
-   
+
             write_file("rock_a.lua", "require('rock_b'); return {}", finally)
             write_file("rock_a-2.0-1.rockspec", [[
                package = "rock_a"
@@ -54,7 +65,7 @@ describe("luarocks.loader", function()
                   "rock_b < 1.0",
                }
                build = {
-                  type = "builtin", 
+                  type = "builtin",
                   modules = {
                      rock_a = "rock_a.lua"
                   }
@@ -64,9 +75,9 @@ describe("luarocks.loader", function()
             print(run.luarocks("make --server=" .. testing_paths.fixtures_dir .. "/a_repo --tree=" .. testing_paths.testing_tree .. " ./rock_b-0.1-1.rockspec"))
             print(run.luarocks("make --server=" .. testing_paths.fixtures_dir .. "/a_repo --tree=" .. testing_paths.testing_tree .. " ./rock_b-1.0-1.rockspec --keep"))
             print(run.luarocks("make --server=" .. testing_paths.fixtures_dir .. "/a_repo --tree=" .. testing_paths.testing_tree .. " ./rock_a-2.0-1.rockspec"))
-   
+
             local output = run.lua([[-e "require 'luarocks.loader'; require('rock_a')"]])
-   
+
             assert.matches("ROCK B 0.1", output, 1, true)
          end)
       end)
diff --git a/src/luarocks/cmd/which.lua b/src/luarocks/cmd/which.lua
index 7503df00..f50a43c3 100644
--- a/src/luarocks/cmd/which.lua
+++ b/src/luarocks/cmd/which.lua
@@ -6,7 +6,6 @@ local which_cmd = {}
 local loader = require("luarocks.loader")
 local cfg = require("luarocks.core.cfg")
 local util = require("luarocks.util")
-local fs = require("luarocks.fs")
 
 function which_cmd.add_to_parser(parser)
    local cmd = parser:command("which", 'Given a module name like "foo.bar", '..
@@ -21,24 +20,17 @@ end
 --- Driver function for "which" command.
 -- @return boolean This function terminates the interpreter.
 function which_cmd.command(args)
-   local pathname, rock_name, rock_version = loader.which(args.modname)
+   local pathname, rock_name, rock_version, where = loader.which(args.modname, "lp")
 
    if pathname then
       util.printout(pathname)
-      util.printout("(provided by " .. tostring(rock_name) .. " " .. tostring(rock_version) .. ")")
-      return true
-   end
-
-   local modpath = args.modname:gsub("%.", "/")
-   for _, v in ipairs({"path", "cpath"}) do
-      for p in package[v]:gmatch("([^;]+)") do
-         local pathname = p:gsub("%?", modpath)  -- luacheck: ignore 421
-         if fs.exists(pathname) then
-            util.printout(pathname)
-            util.printout("(found directly via package." .. v .. " -- not installed as a rock?)")
-            return true
-         end
+      if where == "l" then
+         util.printout("(provided by " .. tostring(rock_name) .. " " .. tostring(rock_version) .. ")")
+      else
+         local key = rock_name
+         util.printout("(found directly via package." .. key.. " -- not installed as a rock?)")
       end
+      return true
    end
 
    return nil, "Module '" .. args.modname .. "' not found."
diff --git a/src/luarocks/loader.lua b/src/luarocks/loader.lua
index 825e4ce7..772fdfcb 100644
--- a/src/luarocks/loader.lua
+++ b/src/luarocks/loader.lua
@@ -194,11 +194,47 @@ end
 
 --- Return the pathname of the file that would be loaded for a module.
 -- @param module string: module name (eg. "socket.core")
--- @return filename of the module (eg. "/usr/local/lib/lua/5.1/socket/core.so"),
--- the rock name and the rock version.
-function loader.which(module)
-   local rock_name, rock_version, file_name = select_module(module, path.which_i)
-   return file_name, rock_name, rock_version
+-- @param where string: places to look for the module. If `where` contains
+-- "l", it will search using the LuaRocks loader; if it contains "p",
+-- it will look in the filesystem using package.path and package.cpath.
+-- You can use both at the same time.
+-- @return If successful, it will return four values.
+-- * If found using the LuaRocks loader, it will return:
+--   * filename of the module (eg. "/usr/local/lib/lua/5.1/socket/core.so"),
+--   * rock name
+--   * rock version
+--   * "l" to indicate the match comes from the loader.
+-- * If found scanning package.path and package.cpath, it will return:
+--   * filename of the module (eg. "/usr/local/lib/lua/5.1/socket/core.so"),
+--   * "path" or "cpath"
+--   * nil
+--   * "p" to indicate the match comes from scanning package.path and cpath.
+-- If unsuccessful, nothing is returned.
+function loader.which(module, where)
+   where = where or "l"
+   if where:match("l") then
+      local rock_name, rock_version, file_name = select_module(module, path.which_i)
+      if rock_name then
+         local fd = io.open(file_name)
+         if fd then
+            fd:close()
+            return file_name, rock_name, rock_version, "l"
+         end
+      end
+   end
+   if where:match("p") then
+      local modpath = module:gsub("%.", "/")
+      for _, v in ipairs({"path", "cpath"}) do
+         for p in package[v]:gmatch("([^;]+)") do
+            local file_name = p:gsub("%?", modpath)  -- luacheck: ignore 421
+            local fd = io.open(file_name)
+            if fd then
+               fd:close()
+               return file_name, v, nil, "p"
+            end
+         end
+      end
+   end
 end
 
 --- Package loader for LuaRocks support.