Mma 10.2 `Alphabet` and `LanguageData` give different and both erroneous list of letters

Question

Bug introduced in 10.2 and fixed in 10.3

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The new function Alphabet introduced in Mathematica 10.2 gives the wrong list of letters for the Spanish language in my system (Windows 7 64 bits).

Alphabet[Entity["Language", "Spanish"]]

{"a", "b", "c", "d", "e", "f", "g", "h", "i", "l", "m", "n", "ñ", "o", "p", "q", "r", "s", "t", "u", "v", "z"}

That list is missing {"j", "k", "w", "x", "y"} and special characters.

The list provided by LanguageData its also wrong

LanguageData["Spanish", "Letters"]

{"a", "á", "b", "c", "d", "e", "é", "f", "g", "h", "i", "í", "j", "l", "m", "n", "ñ", "o", "ó", "p", "q", "r", "s", "t", "u", "ú", "ü", "v", "x", "y", "z"}

as its missing {"k","w"}.

Can anybody reproduce this behaviour in other systems and other languages?

I have filed a report with Wolfram Technical Support [CASE:3388733]

The correct list as given by the Spanish Royal Academy of Language is

a, b, c, d, e, f, g, h, i, j, k, l, m, n, ñ, o, p, q, r, s, t, u, v, w, x, y, z.

Answer 1

Just an extended comment:

The problem seems not to be fixed in v11.1.1 for other "latin" alphabet based languages. Here are some differences between what is returned by Alphabet and LanguageData[lang, "Letters"] for some european countries.

Alphabet seems to do OK, but the problem is that "Letters" do not always include at least all characters returned by Alphabet (below in red).

({#, Grid@
   List@(SequenceAlignment @@ 
      StringJoin /@ 
       Sort /@ {Alphabet[#], 
         LanguageData[#, "Letters"]})} & /@ {"Czech", "Danish", 
 "Dutch", "Finnish", "French", "German", "Hungarian", "Italian", 
 "Polish", "Portuguese", "Romanian", "Slovak", "Slovenian", 
 "Spanish", "Swedish"} // Grid[#, Frame -> All] &) /. {expr : {_, ""} :> Style[expr, Red, Bold], expr : {"", _} :> Style[expr, Blue, Bold]}

For example, here is what is returned for "Danish":

Sort /@ {Alphabet[#], LanguageData[#, "Letters"]} &@"Danish" // Column

where you can see "q","w","x","z" are not returned by LanguageData as indicated in red in the table above.

Answer 2

This was reported to Wolfram Technical Support [CASE:3388733] and acknowledged as a bug.

The problem was fixed in Mathematica 10.3.

Alphabet[Entity["Language", "Spanish"]]

{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "ñ", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"}

LanguageData["Spanish", "Letters"]

{"a", "á", "b", "c", "d", "e", "é", "f", "g", "h", "i", "í", "j", "k", "l", "m", "n", "ñ", "o", "ó", "p", "q", "r", "s", "t", "u", "ú", "ü", "v", "w", "x", "y", "z"}