cmd: dynamically load additional external commands

Instead of a fixed list of commands, a dynamic list of modules
residing within the `luarocks.cmd.external.<cmd_name>` in the Lua path
will be dynamically added. This allows extending LuaRocks with
additional commands.
Same for `luarocks.admin.cmd.external.<cmd_name>`.

4 files changed, 57 insertions, 10 deletions

diff --git a/src/bin/luarocks b/src/bin/luarocks
index d0df0532..18a6179b 100755
--- a/src/bin/luarocks
+++ b/src/bin/luarocks
@@ -1,8 +1,5 @@
 #!/usr/bin/env lua
 
--- this should be loaded first.
-local cfg = require("luarocks.core.cfg")
-
 local loader = require("luarocks.loader")
 local cmd = require("luarocks.cmd")
 
@@ -33,4 +30,4 @@ local commands = {
    test = "luarocks.cmd.test",
 }
 
-cmd.run_command(description, commands, ...)
+cmd.run_command(description, commands, "luarocks.cmd.external", ...)
diff --git a/src/bin/luarocks-admin b/src/bin/luarocks-admin
index e27b8c01..77a51872 100755
--- a/src/bin/luarocks-admin
+++ b/src/bin/luarocks-admin
@@ -13,4 +13,4 @@ local commands = {
    refresh_cache = "luarocks.admin.cmd.refresh_cache",
 }
 
-cmd.run_command(description, commands, ...)
+cmd.run_command(description, commands, "luarocks.admin.cmd.external", ...)
diff --git a/src/luarocks/cmd.lua b/src/luarocks/cmd.lua
index 4200959c..7a7f9654 100644
--- a/src/luarocks/cmd.lua
+++ b/src/luarocks/cmd.lua
@@ -254,12 +254,11 @@ end
 -- Parses input arguments and calls the appropriate driver function
 -- to execute the action requested on the command-line, forwarding
 -- to it any additional arguments passed by the user.
--- Uses the global table "commands", which contains
--- the loaded modules representing commands.
--- @param program_version string: The program version number as a string.
 -- @param description string: Short summary description of the program.
+-- @param commands table: contains the loaded modules representing commands.
+-- @param external_namespace string: where to look for external commands.
 -- @param ... string: Arguments given on the command-line.
-function cmd.run_command(description, commands, ...)
+function cmd.run_command(description, commands, external_namespace, ...)
 
    check_popen()
 
@@ -377,6 +376,12 @@ function cmd.run_command(description, commands, ...)
       os.exit(cmd.errorcodes.OK)
    end
 
+   for _, module_name in ipairs(fs.modules(external_namespace)) do
+      if not commands[module_name] then
+         commands[module_name] = external_namespace.."."..module_name
+      end
+   end
+
    if flags["verbose"] then
       cfg.verbose = true
       fs.verbose()
@@ -386,7 +391,6 @@ function cmd.run_command(description, commands, ...)
       die("Current directory does not exist. Please run LuaRocks from an existing directory.")
    end
 
-   local ok, err
    ok, err = process_tree_flags(flags)
    if not ok then
       die(err)
diff --git a/src/luarocks/fs/lua.lua b/src/luarocks/fs/lua.lua
index 200a1b0c..373dcbdd 100644
--- a/src/luarocks/fs/lua.lua
+++ b/src/luarocks/fs/lua.lua
@@ -166,6 +166,52 @@ function fs_lua.dir(at)
    return coroutine.wrap(function() fs.dir_iterator(at) end)
 end
 
+--- List the Lua modules at a specific require path.
+-- eg. `modules("luarocks.cmd")` would return a list of all LuaRocks command
+-- modules, in the current Lua path.
+function fs_lua.modules(at)
+   at = at or ""
+   if #at > 0 then
+      -- turn require path into file path
+      at = at:gsub("%.", package.config:sub(1,1)) .. package.config:sub(1,1)
+   end
+
+   local path = package.path:sub(-1, -1) == ";" and package.path or package.path .. ";"
+   local paths = {}
+   for location in path:gmatch("(.-);") do
+      if location:lower() == "?.lua" then
+         location = "./?.lua"
+      end
+      local _, q_count = location:gsub("%?", "") -- only use the ones with a single '?'
+      if location:match("%?%.[lL][uU][aA]$") and q_count == 1 then  -- only use when ending with "?.lua"
+         location = location:gsub("%?%.[lL][uU][aA]$", at)
+         table.insert(paths, location)
+      end
+   end
+
+   if #paths == 0 then
+      return {}
+   end
+
+   local modules = {}
+   local is_duplicate = {}
+   for _, path in ipairs(paths) do
+      local files = fs.list_dir(path)
+      for _, filename in ipairs(files or {}) do
+         if filename:match("%.[lL][uU][aA]$") then
+           filename = filename:sub(1,-5) -- drop the extension
+           if not is_duplicate[filename] then
+              is_duplicate[filename] = true
+              table.insert(modules, filename)
+           end
+         end
+      end
+   end
+
+   return modules
+end
+
+
 ---------------------------------------------------------------------
 -- LuaFileSystem functions
 ---------------------------------------------------------------------