[MarkusNeusinger]

Summary

• Posit snapshot noble → resolute in .github/actions/setup-r/action.yml. ubuntu-latest is Ubuntu 26.04 (resolute) now, but the action still installed Posit's 24.04 (noble) binaries. They install without error there, but stringi links libicuuc.so.74/libicui18n.so.74 (checked with readelf), and 26.04 ships ICU 78. So library(stringr) fails with libicui18n.so.74: cannot open shared object file. The snapshot date stays at 2026-10-20, so the ggplot2 4.0.3 note and core/library_versions.py are unchanged.
• R itself needs no change. r-lib/actions/setup-r resolves R 4.6.1 through the r-hub API to Posit's ubuntu-2604 deb on its own, and r-hub names resolute as the matching binary repo.
• The smoke test also loads tidyr and stringr and calls str_detect(). The old smoke test loaded only ggplot2 and ragg, so it passed on the mismatched binaries and hid the failure. A binary built for another Ubuntu release now fails the setup step instead of a generation run.
• The test_version_sources.py fixture models the real line, so it now names resolute too.

Plan

N/A

Test plan

• Container runs on Ubuntu 26.04.1 (resolute). The run: steps of the action ran verbatim after an emulation of r-lib/actions/setup-r: the same r-hub-resolved R deb, its apt prerequisites, and the HTTPUserAgent that makes Posit serve binaries. LANG=C.UTF-8 matches the runners.
  • This branch (resolute): the apt step, 39 packages all installed as binaries, and the new smoke step all pass. line-multi, which loads tidyr, renders 3200×1800 in both themes with correct glyphs.
  • main (noble, negative control): the same steps install and the old smoke step passes. The new smoke step fails with libicui18n.so.74: cannot open shared object file.
• Whole catalogue on both builds. All 325 ggplot2 implementations rendered in light theme on each install.
  • Same result on both: 322 render and 3 fail identically. contour-map-geographic and flowmap-origin-destination need maps, and qrcode-basic needs qrcode; none of these is in the action's install set.
  • No current implementation reaches stringi. tidyr imports stringr lazily, and only separate(), extract() and some pivot_longer() paths call it. So today the mismatch would hit new generations, not the catalogue.
• ruff check, ruff format --check and mypy api core pass. tests/unit/core/test_version_sources.py passes (46), and the ggplot2 pin still resolves to 4.0.3.
• pytest tests/unit tests/integration with -n 4: 12714 passed, 1 failed. The failure is test_host_data.py::test_a_run_that_floods_stderr_past_its_timeout_is_killed_and_reaped, which is unrelated to this diff and passes 3 of 3 in isolation.
• tools.changelog check passes.

Known gaps

• No PR check runs .github/actions/setup-r. Only impl-generate.yml and impl-repair.yml use it, so the 26.04 container run above is the closest proof. The first ggplot2 impl-generate run after the merge is the real test.

Observed, not changed

• setup-julia installs libfreetype6-dev, which is no longer a real package in 26.04. libfreetype-dev (2.14.2+dfsg-1) declares Provides: libfreetype6-dev, and it is the only provider, so apt substitutes it.
• All other apt names in setup-r and setup-julia exist in resolute.

[Copilot]

🔵 Needs a closer look

The shared CI setup change affects runner-dependent binary compatibility and requires final human review.

No open issues 🎉

What changed in this PR

This pull request updates the R setup action for Ubuntu 26.04 (resolute) runners, preventing ICU compatibility failures when loading stringr.

Changes:

• Switches the Posit snapshot repository from noble to resolute.
• Extends the smoke test to load tidyr and stringr and call str_detect().
• Updates the version-source fixture and adds a changelog fragment.

File	Description
tests/​unit/​core/​test_version_sources.py	Aligns the fixture with the updated resolute snapshot URL.
changelog.d/​setup-r-resolute.md	Documents the Ubuntu 26.04 compatibility fix.
.github/​actions/​setup-r/​action.yml	Uses Ubuntu 26.04-compatible R binaries and validates stringr loading.

_{Review effort: Lite}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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