mlc_xcall now properly reports parsing errors

Author: Fabien Fleutot

src/lib/metalua/mlc_xcall.lua

@@ -3,37 +3,70 @@
 
 mlc_xcall = { }
 
+
+-- This is the back-end function, called in a separate lua process
+-- by `mlc_xcall.client_*()' through `os.execute()'.
+--  * inputs:
+--     * the name of a lua source file to compile in a separate process
+--     * the name of a writable file where the resulting ast is dumped
+--       with `serialize()'.
+--  * results:
+--     * an exit status of 0 or -1, depending on whethet compilation
+--       succeeded;
+--     * the ast file filled will either the serialized ast, or the
+--       error message.
 function mlc_xcall.server (luafilename, astfilename)
 
    -- We don't want these to be loaded when people only do client-side business
    require 'metalua.compiler'
    require 'serialize'
 
    -- compile the content of luafile name in an AST, serialized in astfilename
-   local ast = mlc.luafile_to_ast (luafilename)
+   local status, ast = pcall (mlc.luafile_to_ast, luafilename)
    local out = io.open (astfilename, 'w')
-   out:write (serialize (ast))
-   out:close ()
+   if status then -- success
+      out:write (serialize (ast))
+      out:close ()
+      os.exit (0)
+   else -- failure, `ast' is actually the error message
+      out:write (ast)
+      out:close ()
+      os.exit (-1)
+   end      
 end
 
+-- Compile the file whose name is passed as argument, in a separate process,
+-- communicating through a temporary file.
+-- returns:
+--  * true or false, indicating whether the compilation succeeded
+--  * the ast, or the error message.
 function mlc_xcall.client_file (luafile)
 
-   --printf("\n\nmlc_xcall.client_file(%q)\n\n", luafile)
+   -- printf("\n\nmlc_xcall.client_file(%q)\n\n", luafile)
 
    local tmpfilename = os.tmpname()
-   local cmd = string.format ([[lua -l metalua.mlc_xcall -e "mlc_xcall.server('%s', '%s')"]], 
-			      luafile :gsub ([[\]], [[\\]]), 
-			      tmpfilename :gsub([[\]], [[\\]]))
+   local cmd = string.format (
+      [=[lua -l metalua.mlc_xcall -e "mlc_xcall.server([[%s]], [[%s]])"]=], 
+      luafile, tmpfilename)
 
-   --printf("os.execute [[%s]]\n\n", cmd)
+   -- printf("os.execute [[%s]]\n\n", cmd)
 
-   local ret = os.execute (cmd)
-   if ret~=0 then error "xcall failure. FIXME: transmit failure and backtrace" end
-   local ast = (lua_loadfile or loadfile) (tmpfilename) ()
+   local status = (0 == os.execute (cmd))
+   local result -- ast or error msg
+   if status then 
+      result = (lua_loadfile or loadfile) (tmpfilename) ()
+   else
+      local f = io.open (tmpfilename)
+      result = f :read '*a'
+      f :close()
+   end
    os.remove(tmpfilename)
-   return true, ast
+   return status, result
 end
 
+-- Compile a source string into an ast, by dumping it in a tmp
+-- file then calling `mlc_xcall.client_file()'.
+-- returns: the same as `mlc_xcall.client_file()'.
 function mlc_xcall.client_literal (luasrc)
    local srcfilename = os.tmpname()
    local srcfile, msg = io.open (srcfilename, 'w')