Boost: Fix sprintf function call compatibility with Gutenberg 21.2

[LiamSarsfield]

Fixes HOG-219: Cornerstone pages UI broken when Gutenberg plugin is active

Proposed changes:

• Fixed incorrect usage of sprintf() in CornerstoneTitleSummary component where an anonymous function was passed as the second argument instead of calling the function to get its return value

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

N/A

Does this pull request change what data or activity we track or use?

No

Testing instructions:

1. Go to Jetpack Boost settings
2. Navigate to Cornerstone Pages section
3. Verify the title summary displays correctly formatted text instead of raw function code
4. Add/remove cornerstone pages and verify the summary updates correctly
5. Test with different numbers of cornerstone pages (0, 1, multiple)

Compatibility Testing:

• Test with Gutenberg 21.2+ (should work correctly)
• Test with Gutenberg 21.1.1 and earlier (should continue working)
• Test without Gutenberg plugin (should continue working with WordPress core)

Background

Root Cause: The issue was caused by incorrect usage of sprintf() where we passed an anonymous function as the second argument instead of calling the function first.

Why it worked before: WordPress core and Gutenberg ≤21.1.1 used the sprintf-js library that would automatically execute function arguments via its computed values functionality.

What changed: Gutenberg 21.2 updated their @wordpress/i18n implementation to use a standards-compliant sprintf that doesn't execute function arguments, causing the function code to be displayed as text. (WordPress/gutenberg#70434)

The fix: Changed from sprintf(template, functionRef) to sprintf(template, functionRef()) to ensure we pass the actual value instead of the function reference.

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Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/boost/app/assets/src/js/features/cornerstone-pages/cornerstone-pages.tsx	0/13 (0.00%)	0.00%	-2 💚

Full summary · PHP report · JS report

[kraftbj]

Confirmed the bug and that this patch resolves it.

[kraftbj]

I'm going to go ahead and merge this so trunk is good against latest Gutenberg. If there's more to be done @LiamSarsfield , can you note it and open a new PR?

[LiamSarsfield]

If there's more to be done @LiamSarsfield , can you note it and open a new PR?

This is the only culprit of this specific issue I found, though if I encounter any further ones, will do!