Update ixdtf to handle unbound fraction length
#6036
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nekevss
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ixdtf to handle unbound fraction length
utils/ixdtf/src/parsers/records.rs
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| pub enum Fraction { | ||
| /// Parsed nanoseconds value (A fraction value from 1-9 digits length) | ||
| Nanoseconds(u64), | ||
| /// Parsed picoseconds value (A fraction value from 10-12 digits length) | ||
| Picoseconds(u64), | ||
| /// Parsed femtoseconds value (A fraction value from 12-15 digits length) | ||
| Femtoseconds(u64), | ||
| /// A parsed value truncated to nanoseconds (A fraction value of 15+ digits length) | ||
| Truncated(u64), // An unbound fraction value truncated to nanoseconds | ||
| } |
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Suggestion: change this to
pub struct Fraction {
fraction_digits: u8,
value: u64,
}and then give it functions such as
impl Fraction {
pub fn try_to_nanoseconds(self) -> Option<u64> {
if self.fraction_digits <= 9 {
// compute the pow and return
} else {
None
}
}
pub fn to_truncated_nanoseconds(self) -> u64 {
// compute pow, either + or -
}
}Another future advantage of this model is that the Fraction can directly return a FixedDecimal, which could make fractional second formatting more efficient in icu4x.
components/timezone/src/ixdtf.rs
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| @@ -42,6 +42,8 @@ pub enum ParseError { | |||
| InconsistentTimeZoneOffsets, | |||
| /// There was an invalid Offset. | |||
| InvalidOffsetError, | |||
| /// There was an invalid subsecond fraction. | |||
| InvalidFraction, | |||
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I think this is overkill. I'd rather document that sub-nanoseconds are truncated. The formatting code only supports nanosecond precision anyway.
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If not, I'd prefer naming this
/// The string contains precision that is not representable by the output type.
ExcessivePrecisionInvalidFraction is what I'd expect for a string like "12:48:16.a0", which already produces Syntax.
components/timezone/src/ixdtf.rs
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| let Some(nanosecond) = self.time.fraction.to_nanoseconds() else { | ||
| return Err(ParseError::InvalidFraction); | ||
| }; | ||
| let time = Time::try_new( | ||
| self.time.hour, | ||
| self.time.minute, | ||
| self.time.second, | ||
| self.time.nanosecond, | ||
| nanosecond, | ||
| )?; |
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Ideally there'd only be one code path that parses the IXDTF struct into Time, and it should be Time::try_from_ixdtf_record. Please try to use that (also for Date ideally).
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I updated Time with a try_from_time_record method to address this.
I'm not entirely clear what you had meant by also "for Date ideally." Unless the idea was to expose two methods: Time::try_from_time_record and Date::try_from_date_record on the referenced types. So if you were thinking of that or a bit of a different approach, let me know.
utils/ixdtf/src/error.rs
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| @@ -46,6 +46,8 @@ pub enum ParseError { | |||
| TimeSecond, | |||
| #[displaydoc("Invalid character while parsing fraction part value.")] | |||
| FractionPart, | |||
| #[displaydoc("Fraction part value exceeds a representable range.")] | |||
| InvalidFractionRange, | |||
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"Invalid" is not very descriptive. This is an error, that already tells me that something is not valid.
| InvalidFractionRange, | |
| ExcessiveSecondPrecision, |
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I was double checking this and the error is specific to a Duration hour fraction and minute fraction potentially exceeding the range of u64::MAX when calculated. Maybe DurationFractionExceededRange (this would then be moved down into the Duration errors).
This PR updates
ixdtf's fraction handling to parse fraction values beyond 9 digits in length per feedback from #6004.It introduces a new enum
Fractionin place of the previousnanosecondfield that allows parsing fraction values beyond 9 digits while preserving the precision in the enum.It also adds a variety of tests to test the new behavior while adjusting tests from the old behavior to the new behavior