langs/i18n: Revise the plural implementation

[bep]

There were some issues introduced with the plural counting when we upgraded from v1 to v2 of go-i18n.

This commit improves that situation given the following rules:

• A single integer argument is used as plural count and passed to the i18n template as a int type with a .Count method. The latter is to preserve compability with v1.
• Else the plural count is either fetched from the Count/count field/method/map or from the value itself.
• Any data type is accepted, if it can be converted to an integer, that value is used.

The above means that you can now do pass a single integer and both of the below will work:

{{ . }} minutes to read
{{ .Count }} minutes to read

Fixes #8454
Closes #7822
See gohugoio/hugoDocs#1410

[bep]

@jmooring I would appreciate if you could have a look at this. Esp. look at the test cases in TestGetPluralCount to see if they make any sense. Seems that the v1 to v2 upgrade was filled with hassles, but I think this should at least improve the situation.

[bep]

OK, I have an idea of how to make this even better. Will be back in a flash.

[bep]

OK, this should be ready to go.

[jmooring]

A single integer argument is used as plural count

That's not going to provide the expected result with, for example, the Polish language. According to the CLDR plural rules for Polish, 100 is part of the many category, while 100.0 is part the of the other category. In another example, the plural lookup will also fail in languages such as English, Polish, and Norwegian with 1.5.

I have not finished testing yet, but wanted to provide this early feedback. I'm sorry, this stuff is messy.

[jmooring]

I think that allowing both of these constructs will lead to problems.

i18n/en.toml

[cat]
one = "{{ .Count }} cat"
other = "{{ .Count }} cats"

[dog]
one = "{{ . }} dog"
other = "{{ . }} dogs" 

I will have to remember to call {{ T "cat" (dict "Count" 2) }} when translating cat, and {{ T "dog" 2 }} when translating dog. I think it would easier if we could map the single value in my dog example to {{ .Count }} in the TOML file:

[cat]
one = "{{ .Count }} cat"
other = "{{ .Count }} cats"

[dog]
one = "{{ .Count }} dog"
other = "{{ .Count }} dogs" 

And let me call it either way:

{{ T "cat" (dict "Count" 2) }}
{{ T "dog" 2 }}

[bep]

I think that allowing both of these constructs will lead to problems.

The "support both" is just to avoid breaking old templates, and what you suggest isn't technically feasible (or, not without spending a stupid amount of time on it; remember: you can pass any object as context into the translation func).

My thought about this going forward is that:

• You should be able to look at the i18n template and see what it needs, no ".Count" magic
• The plural count is determined by either the single integer (or string, float) argument or if it's a composite, the .Count field method.

I'll merge this. It's certainly an improvement.

[github-actions]

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