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fallible offset conversion #145

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Merged
merged 1 commit into from
May 26, 2025
Merged

fallible offset conversion #145

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11 changes: 8 additions & 3 deletions src/items/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -303,7 +303,7 @@ fn with_timezone_restore(
offset: time::Offset,
at: DateTime<FixedOffset>,
) -> Option<DateTime<FixedOffset>> {
let offset: FixedOffset = chrono::FixedOffset::from(offset);
let offset: FixedOffset = chrono::FixedOffset::try_from(offset).ok()?;
let copy = at;
let x = at
.with_timezone(&offset)
Expand Down Expand Up @@ -360,7 +360,9 @@ fn at_date_inner(date: Vec<Item>, mut d: DateTime<FixedOffset>) -> Option<DateTi
},
..
}) => {
let offset = offset.map(chrono::FixedOffset::from).unwrap_or(*d.offset());
let offset = offset
.and_then(|o| chrono::FixedOffset::try_from(o).ok())
.unwrap_or(*d.offset());

d = new_date(
year.map(|x| x as i32).unwrap_or(d.year()),
Expand All @@ -379,7 +381,10 @@ fn at_date_inner(date: Vec<Item>, mut d: DateTime<FixedOffset>) -> Option<DateTi
second,
offset,
}) => {
let offset = offset.map(chrono::FixedOffset::from).unwrap_or(*d.offset());
let offset = offset
.and_then(|o| chrono::FixedOffset::try_from(o).ok())
.unwrap_or(*d.offset());

d = new_date(
d.year(),
d.month(),
Expand Down
29 changes: 21 additions & 8 deletions src/items/time.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,8 @@ use winnow::{
ModalResult, Parser,
};

use crate::ParseDateTimeError;

use super::{dec_uint, relative, s};

#[derive(PartialEq, Debug, Clone, Default)]
Expand Down Expand Up @@ -95,22 +97,33 @@ impl Offset {
}
}

impl From<Offset> for chrono::FixedOffset {
fn from(
impl TryFrom<Offset> for chrono::FixedOffset {
type Error = ParseDateTimeError;

fn try_from(
Offset {
negative,
hours,
minutes,
}: Offset,
) -> Self {
) -> Result<Self, Self::Error> {
let secs = hours * 3600 + minutes * 60;

if negative {
FixedOffset::west_opt(secs.try_into().expect("secs overflow"))
.expect("timezone overflow")
let offset = if negative {
FixedOffset::west_opt(
secs.try_into()
.map_err(|_| ParseDateTimeError::InvalidInput)?,
)
.ok_or(ParseDateTimeError::InvalidInput)?
} else {
FixedOffset::east_opt(secs.try_into().unwrap()).unwrap()
}
FixedOffset::east_opt(
secs.try_into()
.map_err(|_| ParseDateTimeError::InvalidInput)?,
)
.ok_or(ParseDateTimeError::InvalidInput)?
};

Ok(offset)
}
}

Expand Down
6 changes: 6 additions & 0 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -266,6 +266,12 @@ mod tests {
.and_utc();
assert_eq!(actual, expected);
}

#[test]
fn offset_overflow() {
assert!(parse_datetime("m+12").is_err());
assert!(parse_datetime("24:00").is_err());
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In another PR I had the fuzzer fail on "m1y-12".

Maybe worth adding?
assert!(parse_datetime("m1y-12").is_ok());

(-12 is an acceptable offset)

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Maybe I misunderstand something, but shouldn't it be:

assert!(parse_datetime("m1y-12").is_err());

and

assert!(parse_datetime("m+12").is_ok());

With GNU date I get:

$ date -d "m1y-12"
date: invalid date ‘m1y-12’
$ date -d "m+12"
Sun May 25 02:00:00 AM CEST 2025

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Goodness....

So I have no idea what m1y is supposed to parse to ,-P But it seems like we accept it, while GNU coreutils always rejects it. So I think this is orthogonal to the problem here. So maybe let's drop my suggestion. Filed #147.

BUT, GNU coreutils accepts all offsets between -24 and +24, so we should do that too:

$ date -d "m"
Sun May 25 02:00:00 PM CEST 2025
$ date -d "m+24"
Sat May 24 02:00:00 PM CEST 2025
$ date -d "m+25"
date: invalid date ‘m+25’
$ date -d "m-25"
date: invalid date ‘m-25’
$ date -d "m-24"
Mon May 26 02:00:00 PM CEST 2025

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@yuankunzhang yuankunzhang May 26, 2025 •
edited
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We are using chrono::FixedOffset to represent offsets, which accepts offsets only in the range -24 to +24. Note that the literal m+12 will overflow because the letter m already denotes a +12 offset. Achieving GNU date compatibility in this regard will require re-working the underlining data models. Since this PR is just a trivial fix, I suggest we merge it first and address the larger redesign in a separate effort.

}
}

#[cfg(test)]
Expand Down