Strip fractional seconds in ParseDockerTimestamp#40495
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Pull request overview
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Copilot was unable to run its full agentic suite in this review.
Fixes parsing of Docker ISO 8601 timestamps that include fractional seconds by normalizing the input before std::chrono::parse, preventing valid timestamps (e.g. ...00.123456789Z) from throwing E_INVALIDARG.
Changes:
- Normalize Docker timestamps by stripping the optional fractional seconds portion before parsing.
- Keep existing
%Z-based parsing behavior while ensuring epoch-second precision remains correct.
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I'm not totally sold on this one. |
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Ok, I think I've convinced myself this is real and worth doing. |
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May 12, 2026
The chrono parse format `%FT%H:%M:%S%Z` does not consume the optional fractional seconds component that Docker emits in ISO 8601 timestamps (e.g. `2026-03-05T10:30:00.123456789Z`). For timestamps with a fractional component the parse fails and `THROW_HR_IF_MSG` reports an `E_INVALIDARG` for what is in fact a valid Docker timestamp. Strip the fractional component (between `.` and the timezone marker `Z` / `+` / `-`) before parsing. The function returns epoch seconds, so the dropped sub-second precision is irrelevant. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
The '.' itself can't match 'Z', '+' or '-', so starting find_first_of one past dot makes the intent slightly clearer and avoids an unnecessary comparison. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Drop the %Z portion of the chrono parse format string and remove the fractional-component normalization. std::chrono::parse does not treat unread trailing input as a failure, so '%FT%H:%M:%S' parses Docker timestamps with or without a fractional component and with or without the trailing 'Z' without any pre-processing. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Per review feedback from Copilot: with the format string '%FT%H:%M:%S' chrono::parse silently stops at the seconds field, so an input like '2026-03-05T10:30:00+05:00' would have been treated as UTC and yielded the wrong epoch seconds (this was also the behavior of the original '%Z' parse). Require a trailing 'Z' so non-UTC offsets are rejected. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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| // chrono::parse leaves the trailing fractional component (if any) and the 'Z' | ||
| // unread; that is not treated as a parse failure. | ||
| std::chrono::sys_seconds utcSeconds; | ||
| std::istringstream stream(timestamp); |
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Good catch -- e5a98ba validates the tail is exactly Z or .<digits>Z so garbage between the seconds field and trailing Z is rejected.
Per review feedback from Copilot: simply checking the last character is 'Z' admits malformed suffixes between the seconds field and the trailing 'Z' (e.g. '2026-03-05T10:30:00garbageZ') because std::chrono::parse stops silently at the end of the seconds. Instead, verify that the unconsumed tail after parsing is exactly 'Z' or '.<digits>Z'. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Closing -- could not reproduce the claimed parse failure against current MSVC. The existing |
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Split out from #40489.
The chrono parse format
%FT%H:%M:%S%Zdoes not consume the optional fractional seconds component that Docker emits in ISO 8601 timestamps (e.g.2026-03-05T10:30:00.123456789Z). For timestamps with a fractional component the parse fails and the call throwsE_INVALIDARGfor what is actually a valid Docker timestamp.Change
src/windows/wslcsession/WSLCContainer.cpp: strip the optional fractional component (between.and the timezone markerZ/+/-) before parsing. The function returns epoch seconds, so dropping sub-second precision is correct.Validation
%Zparse forZ/ abbreviated zones still runs unchanged.2026-03-05T10:30:00Z— no., unchanged2026-03-05T10:30:00.123456789Z— fractional stripped beforeZ2026-03-05T10:30:00.123+05:00— fractional stripped before+