Fix tracking_id is minted per CMORiser, not per file

[rhaegar325]

#Solve 689

Fix

Branch fix_tracking_id_issue. base.py, +28 lines: _write_single takes its global attributes from a new helper instead of reading self.ds.attrs directly.

def _file_global_attributes(self) -> Dict[str, Any]:
    attrs = dict(self.ds.attrs)
    existing = attrs.get("tracking_id")
    if isinstance(existing, str) and "/" in existing:
        prefix = existing.rsplit("/", 1)[0]
        attrs["tracking_id"] = f"{prefix}/{uuid.uuid4()}"
    return attrs

Three choices worth recording:

• The prefix is carried over from the existing id, not repeated here, so the CMIP6 (hdl:21.14100) and CMIP7 (hdl:21.14107) handles stay defined in their vocabularies. A dataset with no usable id is left alone.
• A copy is returned. The dataset is reused across split writes, so mutating self.ds.attrs would leak into later files. The returned dict is only ever read downstream (membership check, generate_filename, _build_drs_path, and the write loop), so reference-to-copy changes nothing else.
• creation_date is deliberately not refreshed. Files written in one run legitimately share a creation time, and nothing requires it to differ per file.

Validation

Unit tests — tests/unit/test_tracking_id_per_file.py, 8 tests. Seven cover the helper (distinct ids, prefix preserved, dataset not mutated, other attributes carried through, unusable id left alone); TestSplitWriteMintsIdPerFile drives write() end to end and reads the ids back off disk.

That last one matters: covering only the helper leaves the call site untested — _write_single could revert to self.ds.attrs and the other seven would still pass. Mutation-checked in both directions:

Mutation	Result
call site reverted to self.ds.attrs	1 failed (the end-to-end test)
helper stops minting a new id	3 failed

Full suite: 2108 passed.

Real data — years 101–103 with split_years=1, so one CMORiser writes three files, which is the shape the defect needs:

PASS CMIP7 day tas   : 3 files / 3 unique ids, prefix ok
PASS CMIP6 Omon.tos  : 3 files / 3 unique ids, prefix ok

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.7%. Comparing base (166e8ca) to head (893c187).

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #690   +/-   ##
=====================================
  Coverage   78.6%   78.7%           
=====================================
  Files         41      41           
  Lines       9021    9028    +7     
  Branches    1687    1688    +1     
=====================================
+ Hits        7094    7101    +7     
  Misses      1592    1592           
  Partials     335     335           

Flag	Coverage Δ
unit	78.7% <100.0%> (+<0.1%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.