fix(open): return an error on open/new

The method would not return an error message, now it does,
typically if a conversion is not supported.

README.md

@@ -55,14 +55,29 @@ call to load up the library (that, of course, must be installed in a directory f
 ## API documentation
 
 ```lua
-cd = iconv.new(to, from)
-cd = iconv.open(to, from)
+cd, err = iconv.new(to, from)
+cd, err = iconv.open(to, from)
 ```
 
 Opens a new conversion descriptor, from the 'from' charset to the 'to' charset.
 Concatenating "//TRANSLIT" to the first argument will enable character transliteration and concatenating "//IGNORE" to the first argument will cause iconv to ignore any invalid characters found in the input string.
 
-This function returns a new converter or nil on error.
+The error code, may have any of the following values:
+
+* `nil`
+
+ No error. Creation was successful.
+
+* `iconv.ERROR_INVALID`
+
+ The conversion from `from` to `to` is not supported by the implementation.
+
+* `iconv.ERROR_UNKNOWN`
+
+ There was an unknown error.
+
+
+This function returns a new converter or nil+err on error.
 
 
 ```lua

luaiconv.c

@@ -34,6 +34,7 @@
 
 #include <iconv.h>
 #include <errno.h>
+#include <string.h>
 
 #define LIB_NAME "iconv"
 #define LIB_VERSION LIB_NAME " 7"
@@ -92,11 +93,17 @@ static int Liconv_open(lua_State *L)
  const char *tocode = luaL_checkstring(L, 1);
  const char *fromcode = luaL_checkstring(L, 2);
  iconv_t cd = iconv_open(tocode, fromcode);
- if (cd != (iconv_t)(-1))
+ if (cd != (iconv_t)(-1)) {
  push_iconv_t(L, cd); /* ok */
- else
+ return 1;
+ } else {
  lua_pushnil(L); /* error */
- return 1;
+ if (errno == EINVAL)
+ lua_pushnumber(L, ERROR_INVALID);
+ else
+ lua_pushnumber(L, ERROR_UNKNOWN);
+ return 2;
+ };
 }
 
 /* Use a fixed-size buffer in the stack to avoid a lot of small mallocs
@@ -207,7 +214,7 @@ static int Liconv_close(lua_State *L)
  lua_pushboolean(L, 1); /* ok */
  }
  else
- lua_pushnil(L); /* error */
+ lua_pushnil(L); /* error, called from __gc, so no need for error messsage */
  return 1;
 }
 

test_iconv.lua

@@ -76,20 +76,30 @@ local ebcdic = "\193\150\64\147\150\149\135\133\107\64\129\150\64\147\164\129"
 .. "\37"
 
 
+local function ErrMsg(errno)
+ if errno == iconv.ERROR_INCOMPLETE then
+ return "Incomplete input."
+ elseif errno == iconv.ERROR_INVALID then
+ return "Invalid input."
+ elseif errno == iconv.ERROR_NO_MEMORY then
+ return "Failed to allocate memory."
+ elseif errno == iconv.ERROR_UNKNOWN then
+ return "There was an unknown error."
+ elseif errno == iconv.FINALIZED then
+ return "Handle was already finalized."
+ end
+ return "Unknown error: "..tostring(errno)
+end
+
+
 local function check_one(to, from, text)
  print("\n-- Testing conversion from " .. from .. " to " .. to)
- local cd = iconv.new(to .. "//TRANSLIT", from)
- assert(cd, "Failed to create a converter object.")
+ local cd, errno = iconv.new(to .. "//TRANSLIT", from)
+ assert(cd, ("Failed to create a converter object: %s"):format(ErrMsg(errno)))
  local ostr, err = cd:iconv(text)
 
- if err == iconv.ERROR_INCOMPLETE then
- print("ERROR: Incomplete input.")
- elseif err == iconv.ERROR_INVALID then
- print("ERROR: Invalid input.")
- elseif err == iconv.ERROR_NO_MEMORY then
- print("ERROR: Failed to allocate memory.")
- elseif err == iconv.ERROR_UNKNOWN then
- print("ERROR: There was an unknown error.")
+ if err then
+ print(("ERROR: %s"):format(ErrMsg(err)))
  end
  print(ostr)
 end