Sample
chrono 0.4.42: Parse datetime strings with fixed-length fractional seconds followed by trailing literals without ParseError(TooShort), fixed in chrono 0.4.42
Verified sample for cargo chrono 0.4.42: Parse datetime strings with fixed-length fractional seconds followed by trailing literals without…
sha256:16f5b2fe847fd1153f4755c8bfea4f30e6e6f6ed5be62408dbac23c8eb592e44
This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured.
How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people.
MIT-0
Execution evidence
The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.
- Evidence basis
- Signed contract pass
- Verification receipts
- 2
- Signing keys that built it
- 2
Declared environment
rust linux x64 rust rust cargo
Verification-run environments
| Environment | Contract | Stages | Run |
|---|---|---|---|
| rust 1 · linux alpine/x64 · docker ed25519:d91480838ac982c9 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · cargo@1 |
2026-08-16 |
| rust 1 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · cargo@1 |
2026-08-18 |
Case
HOW- Goal
- Parse datetime strings with fixed-length fractional seconds followed by trailing literals without ParseError(TooShort), fixed in chrono 0.4.42
- Packages
- Symbols
-
- NaiveDateTime::parse_from_str
- NaiveTime::parse_from_str
- Environment
- rust
- Created
- 2026-08-16T04:52:38Z
Contract
- assert NaiveDateTime::parse_from_str parses fixed 6-digit fractions followed by literal characters without returning ParseError(TooShort)
- assert NaiveTime::parse_from_str parses fixed 3-digit fractions followed by literal characters without returning ParseError(TooShort)
- assert NaiveDateTime::parse_from_str parses fixed 9-digit fractions followed by literal characters without returning ParseError(TooShort)
Files
- Cargo.lock
- Cargo.toml
- NOTES.md
- csx.json
- src/lib.rs
Source
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[dependencies]
chrono = { version = "=0.4.42", default-features = false, features = ["std", "clock", "alloc"] }
# Chrono Bugfix Release Verification: Fixed-Length Second Fraction Parsing
## Prior Known Solutions Found
During the initial search using `search_known_solution`, the following samples for `pkg:cargo/chrono` were returned from the CodeSampleX cache:
- `sha256:861889cfdd0a5dd5ceeb51b6ec6359baf342d7c5c30f7d1fbc598a53e175fac2`: Gating chrono features without default features (`clock`, `serde`, `Utc::now`).
- `sha256:bb53a07e8a52f98a3d5f6b3a0c79b1070e860b17949e852a6e2f2c015657ec3f`: Chrono non-deprecated constructors and month arithmetic clamping behavior.
Neither sample tests or proves a specific bugfix release boundary.
---
## Release Identification
- **Package**: `chrono` (crates.io / cargo)
- **Fixed Release**: `0.4.42`
- **Broken Releases**: `0.4.41` (and earlier 0.4.x versions such as `0.4.38`)
- **Release Notes Reference**: `chronotope/chrono` GitHub Release `v0.4.42` notes:
> - Fix incorrect parsing of fixed-length second fractions by @chris-leach in [#1705](https://github.com/chronotope/chrono/pull/1705)
- **Related Issue**: Issue [#1592](https://github.com/chronotope/chrono/issues/1592) (*"Err(ParseError(TooShort)) when parsing datetime with trailing 0"*).
---
## What Was Wrong Before (Chrono <= 0.4.41)
When parsing date or time strings containing fixed-length fractional second specifiers (e.g. `%.6f`, `%.3f`, `%.9f`) followed immediately by literal characters (such as `"0"` in format `"%Y-%m-%d %H:%M:%S%.6f0"` against input `"2024-06-03 20:02:48.6800000"`), the fractional second parser improperly matched the input string boundaries.
Instead of consuming only the specified fixed number of fractional digits and allowing the remaining string to match subsequent format tokens, the parser failed with:
```rust
Err(ParseError(TooShort))
```
Every assertion attempting to parse fixed-length fractions with trailing characters fails on Chrono <= 0.4.41.
---
## What the Fixed Release Does (Chrono >= 0.4.42)
Chrono 0.4.42 correctly parses exactly the requested fixed number of fractional digits and passes the remaining stream to subsequent format items.
Given:
```rust
let parsed = NaiveDateTime::parse_from_str(
"2024-06-03 20:02:48.6800000",
"%Y-%m-%d %H:%M:%S%.6f0",
);
```
Chrono 0.4.42 returns:
```rust
Ok(2024-06-03T20:02:48.680)
```
---
## Failure Mode on Broken Versions
The broken version (`chrono = "=0.4.41"`) **fails loudly** at test execution time:
- The parser returns `Err(ParseError(TooShort))` instead of `Ok(...)`.
- `parsed.expect(...)` panics with message:
```text
thread 'test_fixed_length_6_fraction_with_trailing_literal' panicked at src/lib.rs:17:16:
parsing fixed 6-digit nanosecond fraction followed by literal character should succeed: ParseError(TooShort)
```
- All 3 contract test cases fail with exit code `101`.
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#[cfg(test)]
mod tests {
use chrono::{NaiveDate, NaiveDateTime, NaiveTime};
#[test]
fn test_fixed_length_6_fraction_with_trailing_literal() {
let parsed = NaiveDateTime::parse_from_str(
"2024-06-03 20:02:48.6800000",
"%Y-%m-%d %H:%M:%S%.6f0",
);
let expected = NaiveDate::from_ymd_opt(2024, 6, 3)
.unwrap()
.and_hms_micro_opt(20, 2, 48, 680_000)
.unwrap();
assert_eq!(
parsed.expect("parsing fixed 6-digit nanosecond fraction followed by literal character should succeed"),
expected
);
}
#[test]
fn test_fixed_length_3_fraction_with_trailing_literal() {
let parsed = NaiveTime::parse_from_str(
"20:02:48.1234",
"%H:%M:%S%.3f4",
);
let expected = NaiveTime::from_hms_milli_opt(20, 2, 48, 123).unwrap();
assert_eq!(
parsed.expect("parsing fixed 3-digit millisecond fraction followed by literal character should succeed"),
expected
);
}
#[test]
fn test_fixed_length_9_fraction_with_trailing_literal() {
let parsed = NaiveDateTime::parse_from_str(
"2024-06-03 20:02:48.1234567890",
"%Y-%m-%d %H:%M:%S%.9f0",
);
let expected = NaiveDate::from_ymd_opt(2024, 6, 3)
.unwrap()
.and_hms_nano_opt(20, 2, 48, 123_456_789)
.unwrap();
assert_eq!(
parsed.expect("parsing fixed 9-digit nanosecond fraction followed by literal character should succeed"),
expected
);
}
}