Fix: PluralRules for Czech locale

[alexheb]

I added new Czech PluralRuleDelegate according to Czech grammar. It would break the usage of an old rule, however I don't believe it could have been used in real word. The test should be:

public void SmartFormatPluralTest()
{
    var c = new CustomPluralRuleProvider(Czech);
    string msg = "{0:plural:Nemáte zprávu|Máte {} zprávu|Přišly Vám {} zprávy|Přišlo Vám {} zpráv}!";
    Smart.Format(c, msg, 0).Should().Be("Nemáte zprávu!");
    Smart.Format(c, msg, 1).Should().Be("Máte 1 zprávu!");
    Smart.Format(c, msg, 2).Should().Be("Přišly Vám 2 zprávy!");
    Smart.Format(c, msg, 4).Should().Be("Přišly Vám 4 zprávy!");
    Smart.Format(c, msg, 5).Should().Be("Přišlo Vám 5 zpráv!");
    Smart.Format(c, msg, 6).Should().Be("Přišlo Vám 6 zpráv!");
}

[codecov]

Codecov Report

Base: 96% // Head: 96% // Increases project coverage by +0% 🎉

Coverage data is based on head (fcf2d0f) compared to base (62c1333).
Patch coverage: 100% of modified lines in pull request are covered.

❗ Current head fcf2d0f differs from pull request most recent head 3b0d94a. Consider uploading reports for the commit 3b0d94a to get more accurate results

Additional details and impacted files

@@         Coverage Diff         @@
##           main   #325   +/-   ##
===================================
  Coverage    96%    96%           
===================================
  Files        91     91           
  Lines      3183   3185    +2     
===================================
+ Hits       3067   3069    +2     
  Misses      116    116           

Impacted Files	Coverage Δ
src/SmartFormat/Utilities/PluralRules.cs	100% <100%> (ø)

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[axunonb]

Good catch, Alex, that seems to be consistent with this document as far as I understand without speaking Czech. Assume you're a native speaker 😉
Would be great if you added the unit test(s) to your PR.
May I ask in which context your using Smart.Format?

[alexheb]

Hello,
Thank you for the reply! You sent me a great source which forced me to think more about it. So the result would be:

private static PluralRuleDelegate CzechFix => (value, pluralWordsCount) =>
value == 0 ? 0 : //zero
value == 1 ? 1 : //one
value == -1 ? 1 : //minus one => one
Math.Abs(value).Between(2, 4) ? 2 :    //few
value % 1 == 0 ? 3 :    //many (integers)
4;  //other (fractions)

As you see I noticed that SmartFormat does not serve negative values properly (look at Math.Abs used) and I believe this could be a problem in many languages..?

Note: The other comments can be discussed here: #327

[axunonb]

SmartFormat does not serve negative values

Indeed, only positive arguments are implemented.
Changing this behavior would result in a breaking change, right?

[alexheb]

Hello, so I made final Czech Rule, ignoring negative values. Well, handling them would be breaking change, however - there could be an optional switch i.e. The test for this should be (frankly I don't know where to put it):

    public void SmartFormatPluralCzechTest()   
    {
        var c = new CustomPluralRuleProvider(Czech);
        string den = "{0:plural:Žádný den|{} den|{} dny|{} dní|{} dne}!";
        Assert.Equal("Žádný den!", Smart.Format(c, den, 0));
        Assert.Equal("1 den!", Smart.Format(c, den, 1));
        Assert.Equal("2 dny!", Smart.Format(c, den, 2));
        Assert.Equal("4 dny!", Smart.Format(c, den, 4));
        Assert.Equal("5 dní!", Smart.Format(c, den, 5));
        Assert.Equal("0,5 dne!", Smart.Format(c, den, 0.5));
    }

[axunonb]

ignoring negative values

I went through the unit tests, and there are tests using negative values.
It can be argued whether negative values are really useful, but currently it is possible. Limiting to positive values might be undesirable for some (unknown) cases.