Upgrade Bootstrap

Upgrade Bootstrap / Bootswatch in bslib

Architecture

bslib vendors Bootstrap and Bootswatch via npm, then applies a series of patch files that add bslib-specific features (semantic color functions, Shiny form support, navbar variables, etc.). The build pipeline is:

1. yarn install downloads fresh upstream packages into inst/node_modules/
2. tools/yarn_install.R moves them to inst/lib/, adds vendor prefixes, validates prefixes, downsizes vendor libraries, applies all patches, and generates precompiled CSS
3. tools/main.R runs yarn_install.R plus additional asset scripts (fonts, gfont info, variables article, component sass)

Version pins live in inst/package.json as npm aliases:

"bs5": "npm:bootstrap@5.3.8",
"bsw5": "npm:bootswatch@5.3.8",

Patches live in tools/patches/ and are applied alphabetically by filename via git apply --reject --whitespace=fix. Later patches depend on earlier ones (especially for shared files like _variables.scss).

Upgrade Workflow

Step 1: Update version pins

Edit inst/package.json to bump the target version(s). Only change the versions being upgraded; leave others untouched.

Step 2: Run the build pipeline

Rscript tools/yarn_install.R

This script will stop with an error if any patch fails to apply. When it fails, proceed to Step 3 to fix patches, then re-run from scratch.

Step 3: Fix rejected patches

When patches fail, follow the systematic approach described in references/patch-fixing-guide.md.

Key points:

• Save clean upstream state before any patch application
• Test all patches sequentially to identify every failure (not just the first)
• Fix patches in parallel when possible (use subagents)
• Re-run yarn_install.R from scratch to verify the full sequence

Step 4: Verify the build

After yarn_install.R completes successfully, confirm:

1. R/versions.R shows the new version (auto-generated by the script)
2. No .rej files exist in the working tree
3. Vendor prefix validation passed (part of yarn_install.R)
4. Precompiled CSS was generated in inst/css-precompiled/

Step 5: Check for new/removed Bootswatch themes

List themes in inst/lib/bsw5/dist/ and compare with what existed before. bootswatch_themes() dynamically reads directory names, so new themes are picked up automatically. Check R/bs-theme-preset-bootswatch.R for any hardcoded theme references that might need updating (e.g., bs3compat_navbar_defaults() has a hardcoded BS3 theme list).

Step 6: Check for redundant patches

If all patches applied cleanly, none are redundant. A patch whose changes were upstreamed would fail to apply because the old-state lines wouldn't match. Only investigate redundancy if a patch was already rejected.

Step 7: Report upstream changes and patch edits

Produce a changelog report for the user covering both Bootstrap and Bootswatch changes between the old and new versions. Research the changelogs (GitHub releases, release blog posts, and/or the CHANGELOG.md in the upstream repos) and organize changes into three tiers based on likely impact to bslib and Shiny apps:

Critical — Changes that directly affect bslib's patched files or Shiny component rendering. Examples: Sass variable renames/removals, color-contrast() algorithm changes, form element markup restructuring, navbar API changes, dark mode variable changes.

Notable — Changes that affect commonly used Bootstrap features in Shiny apps but don't directly conflict with bslib patches. Examples: new utility classes, component behavior changes, accessibility improvements, new CSS custom properties, JavaScript API changes for components used in Shiny.

Minor — Bug fixes, docs changes, or changes to features rarely used in Shiny contexts. Examples: RTL fixes, print stylesheet changes, Offcanvas edge cases, carousel fixes.

After the categorized changelog, include a summary of all patch edits that were required during Step 3, listing each modified patch file with a short description of what changed and why (e.g., "updated context for new $nav-underline-link-active-color variable added upstream").

Also include any new/removed Bootswatch themes (from Step 5) and any redundant patches identified (from Step 6) in this report.

Step 8: Run the full asset pipeline (if not already done)

Rscript tools/main.R

This runs yarn_install.R plus download_preset_fonts.R, update_gfont_info.R, expand_variables_article_template.R, and compile_component_sass.R.

Step 9: Run tests and checks

devtools::test()
devtools::check()

Expect existing snapshot tests to potentially need updating if HTML serialization changed (whitespace-only diffs are safe to accept with testthat::snapshot_accept()). Focus on whether any new failures appear that are related to the Bootstrap upgrade.

Step 10: Visual verification

Test Shiny apps and bslib examples with:

• Default Bootstrap 5 theme
• Dark Bootswatch themes (Darkly, Cyborg, Slate, Superhero)
• Light Bootswatch themes (Flatly, Minty, Lux)
• Shiny form elements (checkbox, radio, selectize, sliders)
• Navbar styling

Key Files

Common Upstream Changes That Break Patches

• Variable value changes (e.g., $table-color: $white to initial)
• New variables added between existing ones (context line shifts)
• Removed style blocks (e.g., .nav-item.open removed)
• Stylelint comment additions (e.g., /* stylelint-disable-line */)
• Sass declaration reordering for Dart Sass compatibility
• color-contrast() function changes (WCAG compliance updates)