[Afloat16]

Summary

Trajectory.plot indexes the first coast or deceleration sample even when the corresponding phase is empty, raising IndexError for valid triangular, stationary, sparsely sampled or zero-blend trajectories.

Draw a phase-joining segment only when that phase contains a sample. Preserve the trajectory arrays and the normal phase plotting path.

Numerical results and public behaviour: Numerical trajectory values and public signatures are unchanged. Plotting now completes when a motion phase is empty and preserves every input sample.

The implementation, regression tests and this description were prepared with ChatGPT (GPT-6 Astra Pro). Afloat16 requested the work and authorised submission; human review of this diff has not yet been confirmed, so this PR is a draft.

Related issue

Found through code inspection; no specific issue is linked. The current open PRs were checked for competing fixes.

Validation

The new regressions on the unchanged base report 16 failed, 4 passed (20 new regression cases on the unchanged base). With this change: 20 new regression cases pass; selected trajectory suites: 51 passed, 18 subtests passed.

Five phase configurations in both travel directions and with zero/nonzero time origins; actual Matplotlib data and input immutability are checked. The zero-blend cases use a real Trajectory containing finite constant-velocity data, isolating plotting from a separate generator issue.

Tested on 9f282d8ff952a6ca95d340ae6a62b04e545a302f using Linux/Python 3.12.14 and the actual package with matching native extensions enabled.

MPLBACKEND=Agg PYTHONPATH=src python -m pytest -q tests/test_trapezoidal_empty_plot_phases.py tests/test_trajectory.py tests/test_trajectory_typing_fixes.py tests/test_trapezoidal_profile.py

New test files pass Ruff lint and format checks; git diff --check passes. Existing production-file Ruff diagnostics are unchanged. Mypy reports the same existing Link.py:327 return-type error on the unchanged base and this branch (165 source files checked), with no additional diagnostics. It does not pass cleanly.

Focused suites only; the complete repository suite, docs build and cross-platform CI were not rerun.

Checklist

• Issue claimed, if a corresponding issue is identified.
• PR title follows Conventional Commits.
• Full repository tests pass locally (focused results are reported above).
• Added regression tests for this change.
• The PR is limited to this fix and its tests.
• Numerical and public behaviour changes are stated above.
• The contributor has personally read, run and understood the diff.
• Required CI checks pass.

Prepared with ChatGPT (GPT-6 Astra Pro).

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 9 complexity · 0 duplication

Metric	Results
Complexity	9
Duplication	0

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