ci: remove robot_descriptions caching, built on wrong diagnosis

.github/workflows/ci.yml

@@ -33,22 +33,6 @@ jobs:
       - name: Install package (core, no swift)
         run: pip install .[dev]
 
-      # Model tests (Panda, PR2, UR3/5/10, Jaco, ...) load URDFs via the
-      # robot_descriptions package, which does NOT bundle the actual asset
-      # data — on first use of a given model it lazily `git clone`s a large
-      # upstream asset repo (hundreds of files) straight into this cache dir.
-      # On a fresh runner that clone happens mid-test, competing with our
-      # own --timeout=50 per test, so it's slow and occasionally flaky.
-      # Caching the directory between runs means only the very first run
-      # after this step lands pays that cost; every run after restores
-      # instantly. Bump the "v1" suffix below to force a clean re-fetch if
-      # the cache ever ends up corrupted or stale.
-      - name: Cache robot_descriptions assets
-        uses: actions/cache@v4
-        with:
-          path: ~/.cache/robot_descriptions
-          key: robot-descriptions-v1-${{ runner.os }}
-
       - name: Test (core)
         run: pytest tests/ --ignore=tests/test_blocks.py --timeout=50 --timeout_method=thread -q
 
@@ -86,14 +70,6 @@ jobs:
       - name: Install package
         run: pip install .[dev]
 
-      # See the "Cache robot_descriptions assets" step in test-core above —
-      # same reasoning, this job hits the same lazily-cloned model data.
-      - name: Cache robot_descriptions assets
-        uses: actions/cache@v4
-        with:
-          path: ~/.cache/robot_descriptions
-          key: robot-descriptions-v1-${{ runner.os }}
-
       - name: Test
         run: pytest tests/ --ignore=tests/test_blocks.py --timeout=50 --timeout_method=thread -q
 
@@ -117,14 +93,6 @@ jobs:
       - name: Install package
         run: pip install .[dev]
 
-      # See the "Cache robot_descriptions assets" step in test-core above —
-      # same reasoning, this job hits the same lazily-cloned model data.
-      - name: Cache robot_descriptions assets
-        uses: actions/cache@v4
-        with:
-          path: ~/.cache/robot_descriptions
-          key: robot-descriptions-v1-${{ runner.os }}
-
       - name: Run coverage
         run: pytest tests/ --ignore=tests/test_blocks.py --cov=src/roboticstoolbox --cov-report=xml:coverage.xml -q
 

tech-debt.md

@@ -609,3 +609,41 @@ Watch for recurrence; if it keeps showing up, look at whether `test_IK_GN3`
 seeds its initial joint configuration deterministically and whether the
 tolerance is unreasonably tight for Gauss-Newton specifically (GN is known
 to converge less reliably than LM from some seeds).
+
+---
+
+## Removed: `robot_descriptions` CI caching (was solving the wrong problem)
+
+### Background
+
+PR #530 (2026-07-03) added `actions/cache` steps for `~/.cache/robot_descriptions`
+to `ci.yml`'s `test-core`, `test`, and `coverage` jobs, reasoning that the
+package's lazy `git clone` of upstream asset repos was "slow and
+occasionally flaky" against the per-test `--timeout=50`. That diagnosis was
+wrong: `robot_descriptions` had never been added to `pyproject.toml` at all
+(see the "missing robot_descriptions dependency" fix, 2026-07-04) — every
+run hit `ModuleNotFoundError` immediately, before any clone was ever
+attempted. The caching apparatus was solving a plausible-sounding symptom
+of a problem that didn't exist yet. Removed 2026-07-04 rather than left in
+place now that the real fix has landed.
+
+Two independent reasons this wasn't worth keeping even setting the wrong
+-diagnosis issue aside: the cache key (`robot-descriptions-v1-${{
+runner.os }}`) is keyed only by OS, not Python version, while the `test`
+job's matrix is `os × python-version` — same-OS jobs run in parallel and
+all start cold, so within a single CI run it provided no benefit across
+the 4 Python versions per OS anyway; and the naming-fallback logic in
+`_load_rd_module` (`URDFRobot.py`) that keeps `robot_descriptions`'
+implementation-detail name out of user-facing errors is legitimate,
+separate, correct UX and was *not* removed — only the CI caching steps
+were part of the wrong-theory rabbit hole.
+
+### If CI timing/flakiness resurfaces
+
+Now that `robot_descriptions` is genuinely installed and genuinely
+git-clones on first use of models like YuMi/PR2/UR3/5/10/Jaco, real
+network-fetch time is incurred every run. If that turns out to matter in
+practice, re-add caching with a corrected key that includes
+`matrix.python-version` (or better, restructure so only one job per OS
+does the network fetch and others restore from it) — don't just restore
+this exact removed code.