1415844 - PLURALS should be aware of PluralRules.jsm's ordering of variants

Status: RESOLVED FIXED

(Localization Infrastructure and Tools :: Fluent Migration, enhancement)

Description

[Staś Małolepszy :stas]

Certain plural rules defined in PluralRules.jsm list their categories in a different order than CLDR (of course they do...). Latvian is one example:

  - PluralRules.jsm: one, zero, other [1]
  - CLDR: zero, one, other [2]

The PLURALS transforms should be aware of the differences and migrate variants in the proper order.

[1] https://developer.mozilla.org/en-US/docs/Mozilla/Localization/Localization_and_Plurals#Plural_rule_6_(3_forms)

[2] http://www.unicode.org/cldr/charts/29/supplemental/language_plural_rules.html#lv

Comment 1

[Axel Hecht [:Pike]]

stas, do we know which milestone or prefs bugs this blocks yet?

Comment 2

[Staś Małolepszy :stas]

We don't know yet. I think we'll need this as soon as a single migrated string uses plurals. Zibi, would you help me set the dependencies right here? Which dependencies of bug 1415730 will require PluralRules?

Comment 3

[Zibi Braniecki [:zbraniecki][:gandalf]]

I don't have an answer yet (keeping NI on me). I know that chrome (first milestone) doesn't, and that containers does. I'm not sure yet what will be the second milestone, but I expect General pane to go next and I didn't write a preliminary patch there yet so don't know if we'll need plurals there.

Comment 4

[Zibi Braniecki [:zbraniecki][:gandalf]]

Preferences::General XUL part is the first patch that will be blocked by this (bug 1435912). Setting.

Comment 5

[Staś Małolepszy :stas]

(In reply to Staś Małolepszy :stas from comment #0)
> Certain plural rules defined in PluralRules.jsm list their categories in a
> different order than CLDR (of course they do...). Latvian is one example:
> 
>   - PluralRules.jsm: one, zero, other [1]
>   - CLDR: zero, one, other [2]

Actually, this is not a good example. The plural categories for Latvian in PluralForm.jsm are (zero, one, other), the same as CLDR.

Comment 6

[Staś Małolepszy :stas]

Lithuanian and Arabic are good examples. flod dug into Lithuanian and produced the following summary. Thanks, flod! I also verified this with Rimas on IRC.


Gecko
-----

https://searchfox.org/mozilla-central/source/intl/locale/PluralForm.jsm#56
(n) => n%10==1&&n%100!=11?0:n%10>=2&&(n%100<10||n%100>=20)?2:1

1st form (#0): anything ending in 1, but not 11
2nd form (#1): all the other numbers not covered by #0 and #1
3rd form (#2): ends in 2-9 or 22-99, excluding numbers ending with 1

In CLDR-speak, the order here is (one, other, few), which gives:

    downloadMessage.deleteAll = Pašalinti #1 atsiuntimą?;Pašalinti #1 atsiuntimų?;Pašalinti #1 atsiuntimus?



CLDR
----

http://www.unicode.org/cldr/charts/dev/supplemental/language_plural_rules.html#lt

1st form (one): n % 10 = 1 and n % 100 != 11..19 (anything ending in 1, but not 11)
2nd form (few): n % 10 = 2..9 and n % 100 != 11..19 (ends in 2-9 or 22-99, not covered by 'one')
3rd form (other): any other number

The correct Fluent message should thus read:

    delete-all =
        { $count ->
            [one] Pašalinti { $count } atsiuntimą?
            [few] Pašalinti { $count } atsiuntimus?
           *[other] Pašalinti { $count } atsiuntimų?
        }

Comment 7

[Staś Małolepszy :stas]

The goal of this bug is the change the migration code such that when a string like downloadMessage.deleteAll is migrated to Fluent in Lithuanian, the first part of the legacy string is assigned to the [one] variant, the second part is assigned to the [other] variant, and the third part is assigned to the [few] variant.

Additionally, we should make sure we choose the default variant well. Right now, the last form as defined in .properties is used as the default. Instead, I suggest that we use 'other' and if it doesn't exist, we use 'many'. According to https://hg.mozilla.org/l10n/compare-locales/file/tip/compare_locales/plurals.py all Gecko plural forms have at least one of these categories.

Comment 8

[Staś Małolepszy :stas]

Attachment: WIP Pull Request

If anyone's interested in moving this forward, I submitted a PR with a test.

Comment 9

[Axel Hecht [:Pike]]

Attachment: my take on this pr

Moving over to compare-locales to map gecko to cldr plurals.

The tricky piece here is where to put the default variant in the case where the legacy translation doesn't have enough variants.

Different stages of this PR implement different strategies:

1. use the last variant in cldr order, and make that default
2. copy the last variant in cldr order to the default cldr order, and make that default.