Reproducible CLDR Provenance for iCalendar Time-Zone Mappings

Engineering objective

System challenge

The generated Windows-to-IANA time-zone mapping did not expose the exact CLDR revision behind its data. Fetching moving-branch content without pinning the source could allow the recorded version and generated mapping to diverge.

Constraints

Working within real limits

• ✕Resolve the newest revision that actually touched windowsZones.xml
• ✕Fetch data from the same immutable revision recorded in generated output
• ✕Keep generated provenance machine-readable and human-auditable
• ✕Defend version parsing and output generation against malformed input

Approach

How it was built

1. 01

   Resolved the newest commit touching windowsZones.xml through GitHub’s commits API.

2. 02

   Fetched the XML from that immutable SHA instead of a moving branch.

3. 03

   Recorded the same SHA in the generated module’s version field and source URL.

4. 04

   Added generator, generated-output, ASCII-date, and injection-safety regression coverage.

5. 05

   Addressed successive maintainer review rounds and reran the full project suite.

Workflow

Implementation flow

Technical validation

Implementation evidence

Observable engineering evidence. Discipline: MERGED UPSTREAM

Public evidence

Review the upstream contribution

Outcome

What was delivered

• Four maintainers approved the final revision before merge

• The generator produced 139 entries with one consistent SHA across version and documentation

• 15,984 tests passed with Ruff and Towncrier validation clean

• The pinned two-request workflow prevents version/data mismatch by construction

Technologies

Stack and tools

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