fix(helpers): keep falsy but defined values in fillTemplate

[Arunendra21]

What: Fixes a bug in the fillTemplate helper (packages/react-core/src/helpers/util.ts).

fillTemplate replaced each ${var} with templateVars[match] || '', which also dropped values that are defined but falsy, such as the number 0 or the boolean false. For example:

fillTemplate('${n}', { n: 0 });    // returned '' instead of '0'
fillTemplate('${v}', { v: false }); // returned '' instead of 'false'

This shows up in Pagination. PaginationOptionsMenu passes numeric firstIndex, lastIndex and itemCount into a string toggle template, so an empty data set (itemCount of 0) silently dropped the 0 from the rendered toggle text (for example 1 - 0 of instead of 1 - 0 of 0).

The fix switches || to the nullish coalescing operator ??, so only null or undefined (for example a missing key) fall back to an empty string, while 0 and false are preserved. Missing keys still resolve to an empty string, so existing behavior is unchanged.

Additional issues: none. This was found while reading the helper code.

Testing: added unit tests in util.test.ts covering 0, false, empty string, and missing keys. The existing fillTemplate interpolation test still passes.

Summary by CodeRabbit

• Bug Fixes

  • Template filling now correctly preserves valid falsy values such as 0, false, and empty strings.
  • Missing or null template values continue to be replaced with empty strings.

• Tests

  • Added coverage for falsy and missing template values.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 272119af-a0ee-44b1-a537-b3164e418328

📥 Commits

Reviewing files that changed from the base of the PR and between 4e13e7c and e5fc370.

📒 Files selected for processing (2)

• packages/react-core/src/helpers/__tests__/util.test.ts
• packages/react-core/src/helpers/util.ts

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Walkthrough

fillTemplate now preserves defined falsy values and replaces only null or undefined template values with empty strings. Tests cover these cases.

Changes

fillTemplate behavior

Layer / File(s)	Summary
Nullish fallback and coverage packages/react-core/src/helpers/util.ts, packages/react-core/src/helpers/__tests__/util.test.ts	fillTemplate uses ?? '' to preserve 0, false, and empty strings. Tests cover defined falsy values and missing keys.

Estimated code review effort: 1 (Trivial) | ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: preserving defined falsy values in fillTemplate.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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