fix: unblock CI (codecov GPG flakiness + py21cmfast 4.2 struct rename)

[steven-murray]

Summary

Nearly every job in the Testing matrix on main is currently red (only macos-latest, 3.11 passes). This is pre-existing breakage on main, unrelated to the two open Dependabot PRs (#114, #115) that happen to inherit it. Two independent causes:

• All ubuntu-latest jobs: codecov/codecov-action@v6.0.0's uploader intermittently fails GPG signature verification because of an upstream key-hosting problem (see GPG public key import returns invalid OpenPGP data, blocking Codecov uploads codecov/codecov-action#1955, where a keyserver 404 body gets piped into gpg as if it were key material). Because fail_ci_if_error: true, this flaky third-party step fails the whole job even when all tests pass. Set it to false.
• python 3.12/3.13 jobs on both OSes: tests/test_simulators/test_py21cmfast/test_lightcones.py's mock-cache fixture accesses o.struct.primitive_fields. py21cmfast 4.2 renamed that property to _struct (confirmed against upstream source between v4.1.1 and v4.2 tags of 21cmfast/21cmFAST). Since pyproject.toml pins 21cmFAST>=4.0.0b (floating), pip resolves 4.1.1 on some Python versions and 4.2 on others in CI right now, so the fixture needs to support both attribute names rather than hard-switching to the new one.

Test plan

• Verified the struct->_struct rename directly against the 21cmFAST v4.1.1 and v4.2 tags on GitHub.
• Confirmed via CI logs of PR build(deps): bump release-drafter/release-drafter from 7.2.1 to 7.7.0 #114/build(deps): bump actions/setup-python from 6 to 7 #115 that python 3.11 jobs resolve 21cmFAST==4.1.1 and 3.12/3.13 jobs resolve 21cmFAST==4.2, matching the pass/fail pattern in the matrix.
• CI on this PR should now go green across the full matrix.

Generated with Claude Code

Summary by Sourcery

Unblock the CI test matrix by relaxing a flaky Codecov upload step and updating tests to be compatible with multiple py21cmfast versions.

Bug Fixes:

• Allow the py21cmfast lightcones test fixture to work with both the old struct and new _struct attribute names to avoid version-dependent failures.

CI:

• Configure Codecov uploads to not fail the entire CI job when the uploader intermittently errors due to external GPG key-hosting issues.

Tests:

• Adjust the py21cmfast lightcones mock cache output to access primitive fields via whichever struct attribute is available, ensuring tests pass across supported py21cmfast versions.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

This PR stabilizes the CI test matrix by relaxing Codecov failure handling in the GitHub Actions workflow and updating a py21cmfast test fixture to be compatible with both pre-4.2 and 4.2+ struct attribute names.

File-Level Changes

Change	Details	Files
Prevent flaky Codecov GPG verification failures from failing otherwise-successful CI test jobs.	Updated Codecov upload step configuration so CI does not fail when the uploader encounters GPG signature verification issues. Documented in workflow comments that the failure mode is due to upstream key-hosting problems and that only the coverage upload, not the tests themselves, should be allowed to fail.	.github/workflows/tests.yaml
Make the py21cmfast lightcone test fixture compatible with both struct and _struct attribute naming across 21cmFAST versions.	Introduced a compatibility shim that selects o._struct when present, otherwise falls back to o.struct in the mock cache output helper. Updated primitive field iteration in the fixture to use the resolved struct object rather than assuming a single attribute name.	tests/test_simulators/test_py21cmfast/test_lightcones.py

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[sourcery-ai]

Hey - I've left some high level feedback:

• Instead of relying on a runtime hasattr check for o._struct vs o.struct, consider centralizing this version-dependent logic (e.g., helper function or compatibility layer) so that future py21cmfast struct changes are easier to manage and test.
• Relaxing fail_ci_if_error to false for Codecov avoids flakiness but may hide real upload issues; consider scoping this change (e.g., to affected OS/Python versions) or adding a separate monitoring step so upload failures remain visible.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Instead of relying on a runtime hasattr check for `o._struct` vs `o.struct`, consider centralizing this version-dependent logic (e.g., helper function or compatibility layer) so that future py21cmfast struct changes are easier to manage and test.
- Relaxing `fail_ci_if_error` to false for Codecov avoids flakiness but may hide real upload issues; consider scoping this change (e.g., to affected OS/Python versions) or adding a separate monitoring step so upload failures remain visible.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.75%. Comparing base (5b6b2c8) to head (4ea407f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #116   +/-   ##
=======================================
  Coverage   85.75%   85.75%           
=======================================
  Files          12       12           
  Lines         772      772           
  Branches      189      189           
=======================================
  Hits          662      662           
  Misses         46       46           
  Partials       64       64           

Flag	Coverage Δ
unittests	85.75% <ø> (ø)

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