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Greedy parsing of datetime before time delta #115

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Merged
merged 3 commits into from
Feb 12, 2025
Merged

Greedy parsing of datetime before time delta #115

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f8adcb6
Add passing test for parsing datetime ending in Z
jfinkels Feb 9, 2025
badc887
Greedy parsing of datetime before time delta
jfinkels Feb 9, 2025
2c55db2
Avoid unnecessary slicing when parsing offset
jfinkels Feb 12, 2025
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170 changes: 126 additions & 44 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,8 +21,8 @@ mod parse_time_only_str;
mod parse_weekday;

use chrono::{
DateTime, Datelike, Duration, FixedOffset, Local, LocalResult, NaiveDateTime, TimeZone,
Timelike,
DateTime, Datelike, Duration, FixedOffset, Local, LocalResult, MappedLocalTime, NaiveDateTime,
TimeZone, Timelike,
};

use parse_relative_time::parse_relative_time_at_date;
Expand Down Expand Up @@ -78,11 +78,88 @@ mod format {
pub const YYYYMMDDHHMM_ZULU_OFFSET: &str = "%Y%m%d%H%MZ%z";
pub const YYYYMMDDHHMM_HYPHENATED_OFFSET: &str = "%Y-%m-%d %H:%M %z";
pub const YYYYMMDDHHMMSS_HYPHENATED_OFFSET: &str = "%Y-%m-%d %H:%M:%S %#z";
pub const YYYYMMDDHHMMSS_HYPHENATED_ZULU: &str = "%Y-%m-%d %H:%M:%SZ";
pub const YYYYMMDDHHMMSS_T_SEP_HYPHENATED_OFFSET: &str = "%Y-%m-%dT%H:%M:%S%#z";
pub const YYYYMMDDHHMMSS_T_SEP_HYPHENATED_SPACE_OFFSET: &str = "%Y-%m-%dT%H:%M:%S %#z";
pub const YYYYMMDDHHMMS_T_SEP: &str = "%Y-%m-%dT%H:%M:%S";
pub const UTC_OFFSET: &str = "UTC%#z";
pub const ZULU_OFFSET: &str = "Z%#z";
pub const NAKED_OFFSET: &str = "%#z";

/// Whether the pattern ends in the character `Z`.
pub(crate) fn is_zulu(pattern: &str) -> bool {
pattern == YYYYMMDDHHMMSS_HYPHENATED_ZULU
}

/// Patterns for datetimes with timezones.
///
/// These are in decreasing order of length. The same pattern may
/// appear multiple times with different lengths if the pattern
/// accepts input strings of different lengths. For example, the
/// specifier `%#z` accepts two-digit time zone offsets (`+00`)
/// and four-digit time zone offsets (`+0000`).
pub(crate) const PATTERNS_TZ: [(&str, usize); 9] = [
(YYYYMMDDHHMMSS_HYPHENATED_OFFSET, 25),
(YYYYMMDDHHMMSS_T_SEP_HYPHENATED_SPACE_OFFSET, 25),
(YYYYMMDDHHMMSS_T_SEP_HYPHENATED_OFFSET, 24),
(YYYYMMDDHHMMSS_HYPHENATED_OFFSET, 23),
(YYYYMMDDHHMMSS_T_SEP_HYPHENATED_OFFSET, 22),
(YYYYMMDDHHMM_HYPHENATED_OFFSET, 22),
(YYYYMMDDHHMM_UTC_OFFSET, 20),
(YYYYMMDDHHMM_OFFSET, 18),
(YYYYMMDDHHMM_ZULU_OFFSET, 18),
];

/// Patterns for datetimes without timezones.
///
/// These are in decreasing order of length.
pub(crate) const PATTERNS_NO_TZ: [(&str, usize); 8] = [
(YYYYMMDDHHMMSS, 29),
(POSIX_LOCALE, 24),
(YYYYMMDDHHMMSS_HYPHENATED_ZULU, 20),
(YYYYMMDDHHMMS_T_SEP, 19),
(YYYYMMDDHHMMS, 19),
(YYYY_MM_DD_HH_MM, 16),
(YYYYMMDDHHMM_DOT_SS, 15),
(YYYYMMDDHHMM, 12),
];

/// Patterns for dates with neither times nor timezones.
///
/// These are in decreasing order of length. The same pattern may
/// appear multiple times with different lengths if the pattern
/// accepts input strings of different lengths. For example, the
/// specifier `%m` accepts one-digit month numbers (like `2`) and
/// two-digit month numbers (like `02` or `12`).
pub(crate) const PATTERNS_DATE_NO_TZ: [(&str, usize); 8] = [
(ISO_8601, 10),
(MMDDYYYY_SLASH, 10),
(ISO_8601, 9),
(MMDDYYYY_SLASH, 9),
(ISO_8601, 8),
(MMDDYY_SLASH, 8),
(MMDDYYYY_SLASH, 8),
(ISO_8601_NO_SEP, 8),
];

/// Patterns for lone timezone offsets.
///
/// These are in decreasing order of length. The same pattern may
/// appear multiple times with different lengths if the pattern
/// accepts input strings of different lengths. For example, the
/// specifier `%#z` accepts two-digit time zone offsets (`+00`)
/// and four-digit time zone offsets (`+0000`).
pub(crate) const PATTERNS_OFFSET: [(&str, usize); 9] = [
(UTC_OFFSET, 9),
(UTC_OFFSET, 8),
(ZULU_OFFSET, 7),
(UTC_OFFSET, 6),
(ZULU_OFFSET, 6),
(NAKED_OFFSET, 6),
(NAKED_OFFSET, 5),
(ZULU_OFFSET, 4),
(NAKED_OFFSET, 3),
];
}

/// Parses a time string and returns a `DateTime` representing the
Expand Down Expand Up @@ -161,33 +238,33 @@ pub fn parse_datetime_at_date<S: AsRef<str> + Clone>(
// sign, then insert a 0 between the sign and the digit to make it
// possible for `chrono` to parse it.
let pattern = Regex::new(r"([\+-])(\d)$").unwrap();
let s = pattern.replace(s.as_ref(), "${1}0${2}");
for fmt in [
format::YYYYMMDDHHMM_OFFSET,
format::YYYYMMDDHHMM_HYPHENATED_OFFSET,
format::YYYYMMDDHHMMSS_HYPHENATED_OFFSET,
format::YYYYMMDDHHMMSS_T_SEP_HYPHENATED_OFFSET,
format::YYYYMMDDHHMM_UTC_OFFSET,
format::YYYYMMDDHHMM_ZULU_OFFSET,
] {
if let Ok(parsed) = DateTime::parse_from_str(s.as_ref(), fmt) {
return Ok(parsed);
let tmp_s = pattern.replace(s.as_ref(), "${1}0${2}");
for (fmt, n) in format::PATTERNS_TZ {
if tmp_s.len() >= n {
if let Ok(parsed) = DateTime::parse_from_str(&tmp_s[0..n], fmt) {
return Ok(parsed);
}
}
}

// Parse formats with no offset, assume local time
for fmt in [
format::YYYYMMDDHHMMS_T_SEP,
format::YYYYMMDDHHMM,
format::YYYYMMDDHHMMS,
format::YYYYMMDDHHMMSS,
format::YYYY_MM_DD_HH_MM,
format::YYYYMMDDHHMM_DOT_SS,
format::POSIX_LOCALE,
] {
if let Ok(parsed) = NaiveDateTime::parse_from_str(s.as_ref(), fmt) {
if let Ok(dt) = naive_dt_to_fixed_offset(date, parsed) {
return Ok(dt);
for (fmt, n) in format::PATTERNS_NO_TZ {
if s.as_ref().len() >= n {
if let Ok(parsed) = NaiveDateTime::parse_from_str(&s.as_ref()[0..n], fmt) {
// Special case: `chrono` can only parse a datetime like
// `2000-01-01 01:23:45Z` as a naive datetime, so we
// manually force it to be in UTC.
if format::is_zulu(fmt) {
match FixedOffset::east_opt(0)
.unwrap()
.from_local_datetime(&parsed)
{
MappedLocalTime::Single(datetime) => return Ok(datetime),
_ => return Err(ParseDateTimeError::InvalidInput),
}
} else if let Ok(dt) = naive_dt_to_fixed_offset(date, parsed) {
return Ok(dt);
}
}
}
}
Expand Down Expand Up @@ -222,16 +299,13 @@ pub fn parse_datetime_at_date<S: AsRef<str> + Clone>(

let ts = s.as_ref().to_owned() + " 0000";
// Parse date only formats - assume midnight local timezone
for fmt in [
format::ISO_8601,
format::ISO_8601_NO_SEP,
format::MMDDYYYY_SLASH,
format::MMDDYY_SLASH,
] {
let f = fmt.to_owned() + " %H%M";
if let Ok(parsed) = NaiveDateTime::parse_from_str(&ts, &f) {
if let Ok(dt) = naive_dt_to_fixed_offset(date, parsed) {
return Ok(dt);
for (fmt, n) in format::PATTERNS_DATE_NO_TZ {
if ts.len() >= n + 5 {
let f = fmt.to_owned() + " %H%M";
if let Ok(parsed) = NaiveDateTime::parse_from_str(&ts[0..n + 5], &f) {
if let Ok(dt) = naive_dt_to_fixed_offset(date, parsed) {
return Ok(dt);
}
}
}
}
Expand All @@ -240,15 +314,13 @@ pub fn parse_datetime_at_date<S: AsRef<str> + Clone>(
// offsets, so instead we replicate parse_date behaviour by getting
// the current date with local, and create a date time string at midnight,
// before trying offset suffixes
let ts = format!("{}0000{}", date.format("%Y%m%d"), s);
for fmt in [
format::UTC_OFFSET,
format::ZULU_OFFSET,
format::NAKED_OFFSET,
] {
let f = format::YYYYMMDDHHMM.to_owned() + fmt;
if let Ok(parsed) = DateTime::parse_from_str(&ts, &f) {
return Ok(parsed);
let ts = format!("{}0000{}", date.format("%Y%m%d"), tmp_s.as_ref());
for (fmt, n) in format::PATTERNS_OFFSET {
if ts.len() == n + 12 {
let f = format::YYYYMMDDHHMM.to_owned() + fmt;
if let Ok(parsed) = DateTime::parse_from_str(&ts[0..n + 12], &f) {
return Ok(parsed);
}
}
}

Expand Down Expand Up @@ -575,4 +647,14 @@ mod tests {
assert_eq!(result, Err(ParseDateTimeError::InvalidInput));
}
}

#[test]
fn test_datetime_ending_in_z() {
use crate::parse_datetime;
use chrono::{TimeZone, Utc};

let actual = parse_datetime("2023-06-03 12:00:01Z").unwrap();
let expected = Utc.with_ymd_and_hms(2023, 6, 3, 12, 0, 1).unwrap();
assert_eq!(actual, expected);
}
}