[Admin] Fix tailwindcss-rails Version to v3 for Solidus Admin Compatibility

[swamp09]

Background

Currently, running bin/rails solidus_admin:tailwindcss:install installs the latest v4 of tailwindcss-rails. This causes compatibility issues because Solidus Admin expects the Tailwind CSS v3 configuration.

Tailwind CSS v4 introduces CSS First Configuration, which alters the structure and handling of the tailwind.config.js file. Using v4 results in a configuration where tailwind.config.js does not function properly. Reference: https://tailwindcss.com/blog/tailwindcss-v4#css-first-configuration

While ideally, Solidus Admin should be updated to work with Tailwind CSS v4 and later, we have restricted it to v3 for now to ensure correct functionality. Additionally, the maintainers of tailwindcss-rails do not recommend upgrading to v4 at this time (see: https://github.com/rails/tailwindcss-rails?tab=readme-ov-file#you-dont-_have_-to-upgrade).

Solution

Modified the installation command in install_tailwindcss.rb to explicitly install v3:

unless bundle_command "show tailwindcss-rails"
  bundle_command "add tailwindcss-rails --version '~>3.0'"
end

This change ensures that running bin/rails solidus_admin:tailwindcss:install installs Tailwind CSS v3, which is compatible with Solidus Admin's current configuration.

If there is anything else that should be added or any improvements that can be made, please let me know.

Checklist

Check out our PR guidelines for more details.

The following are mandatory for all PRs:

• I agree that my PR will be published under the same license as Solidus.
• I have written a thorough PR description.
• I have kept my commits small and atomic.
• I have used clear, explanatory commit messages.

The following are not always needed:

• 📖 I have updated the README to account for my changes.
• 📑 I have documented new code with YARD.
• 🛣️ I have opened a PR to update the guides.
• ✅ I have added automated tests to cover my changes.
• 📸 I have attached screenshots to demo visual changes.

[tvdeyen]

Thanks. 🙏

Note: We really need to think about compiling the stylesheets and js files into the gem and simply serve it from whatever tool the app uses (sprockets or propshaft)

For now this fixes installation issues.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 88.81%. Comparing base (08207da) to head (50db6ad).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
admin/lib/solidus_admin/install_tailwindcss.rb	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6135   +/-   ##
=======================================
  Coverage   88.81%   88.81%           
=======================================
  Files         835      835           
  Lines       18146    18146           
=======================================
  Hits        16116    16116           
  Misses       2030     2030           

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