Proposed patch removes over 400 entities from locale alias tables. They are redundant because they can be calculated on fly.

Also it enables utf8 aliases. Now this adds not hundreds of redundant aliases, but only 8 new locales:

+    'be_bg.utf8':                           'bg_BG.UTF-8',
+    'c.utf8':                               'en_US.UTF-8',
+    'en_dl.utf8':                           'en_DL.UTF-8',
+    'en_zw.utf8':                           'en_ZS.UTF-8',
+    'pa_pk.utf8':                           'pa_PK.UTF-8',
+    'sr_yu.utf8':                           'sr_RS.UTF-8',
+    'te_in.utf8':                           'te_IN.UTF-8',
+    'zh_sg.utf8':                           'zh_SG.UTF-8',

Example.

     'br_fr':                                'br_FR.ISO8859-1',
-    'br_fr.iso88591':                       'br_FR.ISO8859-1',
-    'br_fr.iso885914':                      'br_FR.ISO8859-14',
-    'br_fr.iso885915':                      'br_FR.ISO8859-15',
-    'br_fr.iso885915@euro':                 'br_FR.ISO8859-15',
-    'br_fr.utf8@euro':                      'br_FR.UTF-8',
-    'br_fr@euro':                           'br_FR.ISO8859-15',

Only one of 7 br_fr entities are left. For br_fr.iso88591, br_fr.iso885914 and br_fr.iso885915 just replaced encoding of base br_fr locale. For br_fr.iso885915@euro and br_fr.utf8@euro the @euro modifier is dropped because ISO8859-15 and UTF-8 already contains the euro character. For br_fr@euro default ISO8859-1 encoding replaced to ISO8859-15 and the @euro modifier is dropped.

So now the table contains only base entities which map lang_country to lang_country.encoding and special cases for deprecated and obscure aliases.

On 21.12.2013 20:33, Serhiy Storchaka wrote:
> 
> Serhiy Storchaka added the comment:
> 
> Example.
> 
>      'br_fr':                                'br_FR.ISO8859-1',
> -    'br_fr.iso88591':                       'br_FR.ISO8859-1',
> -    'br_fr.iso885914':                      'br_FR.ISO8859-14',
> -    'br_fr.iso885915':                      'br_FR.ISO8859-15',
> -    'br_fr.iso885915@euro':                 'br_FR.ISO8859-15',
> -    'br_fr.utf8@euro':                      'br_FR.UTF-8',
> -    'br_fr@euro':                           'br_FR.ISO8859-15',
> 
> Only one of 7 br_fr entities are left. For br_fr.iso88591, br_fr.iso885914 and br_fr.iso885915 just replaced encoding of base br_fr locale. For br_fr.iso885915@euro and br_fr.utf8@euro the @euro modifier is dropped because ISO8859-15 and UTF-8 already contains the euro character. For br_fr@euro default ISO8859-1 encoding replaced to ISO8859-15 and the @euro modifier is dropped.
> 
> So now the table contains only base entities which map lang_country to lang_country.encoding and special cases for deprecated and obscure aliases.

Looks like an interesting approach, but I'd like to think about it
a day or two.

Some notes:
* the patch seems to include some unrelated changes, e.g. the
  devanagari fixes and a few new mappings
* the optimize step is called twice for some reason - is this
  intended ? if yes, please add a comment why this is done
* the patch would need some tests to make sure that the removed
  aliases indeed still map to the correct C locale strings

Thanks,
-- 
Marc-Andre Lemburg
eGenix.com

> * the patch seems to include some unrelated changes, e.g. the
>   devanagari fixes and a few new mappings

May be. In any case I have added issue20027 as dependency. New mappings were 
added when enable UTF-8 locales in makelocalealias.py (I can split this in 
separate issue).

> * the optimize step is called twice for some reason - is this
>   intended ? if yes, please add a comment why this is done

Actually we should call it in a loop while the size of the table is decreased.

> * the patch would need some tests to make sure that the removed
>   aliases indeed still map to the correct C locale strings

Currently the makelocalealias.py is such manual test. test_locale contains 
multiple tests for different locales. I'll add several new cases.

I thought some more about this approach. I'm +1 on it. The locale
lookup is not time critical, so the table optimization makes sense.
Nice idea, Serhiy !

On 22.12.2013 00:38, Serhiy Storchaka wrote:
> 
> Serhiy Storchaka added the comment:
> 
>> * the patch seems to include some unrelated changes, e.g. the
>>   devanagari fixes and a few new mappings
> 
> May be. In any case I have added issue20027 as dependency. New mappings were 
> added when enable UTF-8 locales in makelocalealias.py (I can split this in 
> separate issue).

I think it's better to apply the patches separately, if that's
possible.

>> * the optimize step is called twice for some reason - is this
>>   intended ? if yes, please add a comment why this is done
> 
> Actually we should call it in a loop while the size of the table is decreased.

Ok, that makes sense. Still, please add a comment on why this is necessary.

>> * the patch would need some tests to make sure that the removed
>>   aliases indeed still map to the correct C locale strings
> 
> Currently the makelocalealias.py is such manual test. test_locale contains 
> multiple tests for different locales. I'll add several new cases.

Great.

Thanks,
-- 
Marc-Andre Lemburg
eGenix.com

Here is updated patch. It doesn't include any additions to locale alias table (including devanagari). Added several tests cases (many other test cases for removed aliases already exist). optimize() is called only once, looks as second run has no effect until UTF-8 aliases are enabled.

On 26.12.2013 21:19, Serhiy Storchaka wrote:
> 
> Here is updated patch. It doesn't include any additions to locale alias table (including devanagari). Added several tests cases (many other test cases for removed aliases already exist). optimize() is called only once, looks as second run has no effect until UTF-8 aliases are enabled.

Looks good. Could you add a test for the optimization function ?

It should make sure that a complete set of now removed locale
names are properly optimized away, e.g.

     'nl_nl':                                'nl_NL.ISO8859-1',
-    'nl_nl.88591':                          'nl_NL.ISO8859-1',
-    'nl_nl.iso88591':                       'nl_NL.ISO8859-1',
-    'nl_nl.iso885915':                      'nl_NL.ISO8859-15',
-    'nl_nl.iso885915@euro':                 'nl_NL.ISO8859-15',
-    'nl_nl.utf8@euro':                      'nl_NL.UTF-8',
-    'nl_nl@euro':                           'nl_NL.ISO8859-15',

and

     'ja_jp':                                'ja_JP.eucJP',
-    'ja_jp.ajec':                           'ja_JP.eucJP',
     'ja_jp.euc':                            'ja_JP.eucJP',
-    'ja_jp.eucjp':                          'ja_JP.eucJP',
-    'ja_jp.iso-2022-jp':                    'ja_JP.JIS7',
-    'ja_jp.iso2022jp':                      'ja_JP.JIS7',
-    'ja_jp.jis':                            'ja_JP.JIS7',
-    'ja_jp.jis7':                           'ja_JP.JIS7',
     'ja_jp.mscode':                         'ja_JP.SJIS',
     'ja_jp.pck':                            'ja_JP.SJIS',
-    'ja_jp.sjis':                           'ja_JP.SJIS',
-    'ja_jp.ujis':                           'ja_JP.eucJP',

This should then cover all the Latin-1 encodings and also
an Asian one.

Thanks,
-- 
Marc-Andre Lemburg
eGenix.com

> Could you add a test for the optimization function ?

I have no ideas. The optimization function is a part of the makelocalealias.py 
which ran manually very rarely (last time 3.5 year ago). It isn't exposed 
outside the script and I'm not sure that it worths the complication of the 
testing.

> It should make sure that a complete set of now removed locale
> names are properly optimized away, e.g.
> 
>      'nl_nl':                                'nl_NL.ISO8859-1',
> -    'nl_nl.88591':                          'nl_NL.ISO8859-1',
> -    'nl_nl.iso88591':                       'nl_NL.ISO8859-1',
> -    'nl_nl.iso885915':                      'nl_NL.ISO8859-15',
> -    'nl_nl.iso885915@euro':                 'nl_NL.ISO8859-15',
> -    'nl_nl.utf8@euro':                      'nl_NL.UTF-8',
> -    'nl_nl@euro':                           'nl_NL.ISO8859-15',

These cases are covered by test_english and test_euro_modifier.

>      'ja_jp':                                'ja_JP.eucJP',
> -    'ja_jp.ajec':                           'ja_JP.eucJP',
>      'ja_jp.euc':                            'ja_JP.eucJP',
> -    'ja_jp.eucjp':                          'ja_JP.eucJP',
> -    'ja_jp.iso-2022-jp':                    'ja_JP.JIS7',
> -    'ja_jp.iso2022jp':                      'ja_JP.JIS7',
> -    'ja_jp.jis':                            'ja_JP.JIS7',
> -    'ja_jp.jis7':                           'ja_JP.JIS7',
>      'ja_jp.mscode':                         'ja_JP.SJIS',
>      'ja_jp.pck':                            'ja_JP.SJIS',
> -    'ja_jp.sjis':                           'ja_JP.SJIS',
> -    'ja_jp.ujis':                           'ja_JP.eucJP',

Here is a test which includes tests for japanese cases end tests for the euc 
encoding (it maps to different encodings depending on language).

On 26.12.2013 22:43, Serhiy Storchaka wrote:
> 
> Serhiy Storchaka added the comment:
> 
>> Could you add a test for the optimization function ?
> 
> I have no ideas. The optimization function is a part of the makelocalealias.py 
> which ran manually very rarely (last time 3.5 year ago). It isn't exposed 
> outside the script and I'm not sure that it worths the complication of the 
> testing.

I probably wasn't clear: I meant some tests that show that the
alias definitions (on the left) from the X11 file are actually mapped to the
correct alias locales (on the right).

>> It should make sure that a complete set of now removed locale
>> names are properly optimized away, e.g.
>>
>>      'nl_nl':                                'nl_NL.ISO8859-1',
>> -    'nl_nl.88591':                          'nl_NL.ISO8859-1',
>> -    'nl_nl.iso88591':                       'nl_NL.ISO8859-1',
>> -    'nl_nl.iso885915':                      'nl_NL.ISO8859-15',
>> -    'nl_nl.iso885915@euro':                 'nl_NL.ISO8859-15',
>> -    'nl_nl.utf8@euro':                      'nl_NL.UTF-8',
>> -    'nl_nl@euro':                           'nl_NL.ISO8859-15',
> 
> These cases are covered by test_english and test_euro_modifier.

Ok.

>>      'ja_jp':                                'ja_JP.eucJP',
>> -    'ja_jp.ajec':                           'ja_JP.eucJP',
>>      'ja_jp.euc':                            'ja_JP.eucJP',
>> -    'ja_jp.eucjp':                          'ja_JP.eucJP',
>> -    'ja_jp.iso-2022-jp':                    'ja_JP.JIS7',
>> -    'ja_jp.iso2022jp':                      'ja_JP.JIS7',
>> -    'ja_jp.jis':                            'ja_JP.JIS7',
>> -    'ja_jp.jis7':                           'ja_JP.JIS7',
>>      'ja_jp.mscode':                         'ja_JP.SJIS',
>>      'ja_jp.pck':                            'ja_JP.SJIS',
>> -    'ja_jp.sjis':                           'ja_JP.SJIS',
>> -    'ja_jp.ujis':                           'ja_JP.eucJP',
> 
> Here is a test which includes tests for japanese cases end tests for the euc 
> encoding (it maps to different encodings depending on language).

Thanks. I think this is good enough now.

> I probably wasn't clear: I meant some tests that show that the
> alias definitions (on the left) from the X11 file are actually mapped to the
> correct alias locales (on the right).

This is how the optimization function works. It updates alias table with the 
X11 file, and then removes the alias entities one by one and checks that the 
alias definition are mapped to to correct alias locales.

Here is a patch which adds a self-check in the makelocalealias.py script.

On 26.12.2013 23:19, Serhiy Storchaka wrote:
> 
> Serhiy Storchaka added the comment:
> 
>> I probably wasn't clear: I meant some tests that show that the
>> alias definitions (on the left) from the X11 file are actually mapped to the
>> correct alias locales (on the right).
> 
> This is how the optimization function works. It updates alias table with the 
> X11 file, and then removes the alias entities one by one and checks that the 
> alias definition are mapped to to correct alias locales.
> 
> Here is a patch which adds a self-check in the makelocalealias.py script.

Thanks, this makes that part of the implementation waterproof as well.

Good to go, I guess.

New changeset 63bc68d7f449 by Serhiy Storchaka in branch 'default':
Issue #20046: Locale alias table no longer contains entities which can be
http://hg.python.org/cpython/rev/63bc68d7f449

Thank you Marc-Andre for your reviews.