fix(titleCase): extra spaces when input already contains spaces

[guoyangzhen]

Fixes #96

Problem

titleCase('Hello World') produces 'Hello World' (double space). Calling titleCase(titleCase('hello')) also produces double spaces because splitByCase does not recognize space as a separator.

Root cause: splitByCase uses STR_SPLITTERS = ['-', '_', '/', '.'] but does not include space. When processing 'Hello World', the falling-edge detection at the space character (uppercase W → space) splits the string incorrectly, attaching the space to the preceding token: ['Hello ', 'World'].

Fix

Added space to STR_SPLITTERS. Now splitByCase('Hello World') correctly returns ['Hello', 'World'], and titleCase joins them with a single space.

This also improves camelCase, kebabCase, snakeCase, etc. for space-separated input.

Tests

• All existing 63 tests pass
• Added 3 new test cases: Hello World, hello world, Hello World
• Verified titleCase is now idempotent: titleCase(titleCase('hello')) === 'Hello'

Summary by CodeRabbit

• Bug Fixes

  • Improved text splitting behavior by properly treating spaces as delimiters during case-based operations.
  • Enhanced whitespace normalization when formatting text in title case, now correctly handling multiple consecutive spaces.

• Tests

  • Expanded test coverage for multi-word input scenarios and whitespace handling edge cases.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR fixes a bug in the titleCase function where spaces were being incorrectly handled during string splitting. A space character was added to the default string splitters configuration, and test cases were added to validate the fix properly handles already title-cased strings and multiple spaces.

Changes

Cohort / File(s)	Summary
String Splitter Configuration src/index.ts	Added space character to STR_SPLITTERS to properly treat spaces as delimiter boundaries during string splitting operations.
Test Coverage test/scule.test.ts	Extended titleCase test suite with three new cases covering already title-cased strings, lowercase multi-word input, and input with multiple consecutive spaces.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

🐰 A space was lost in our splitting dance,
Now words align with proper stance,
No extra gaps in titles bright,
Each word's placement crystal right! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 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 fix addressing the core issue of extra spaces being inserted by titleCase when handling space-separated input.
Linked Issues check	✅ Passed	The pull request successfully addresses all requirements from issue #96: adding space to STR_SPLITTERS fixes titleCase to handle space-separated input without inserting extra spaces, making it idempotent.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing the titleCase spacing issue; no unrelated modifications to other functionality or files are present.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

test/scule.test.ts (1)

136-149: Add an explicit idempotency assertion for titleCase.

This suite now covers input variants well; adding one direct nested-call check would lock the issue objective more explicitly.

Suggested test addition

 describe("titleCase", () => {
   test.each([
     ["", ""],
     ["f", "F"],
     ["foo", "Foo"],
     ["foo-bar", "Foo Bar"],
     ["this-IS-aTitle", "This is a Title"],
     ["Hello World", "Hello World"],
     ["hello world", "Hello World"],
     ["Hello  World", "Hello World"],
   ])("%s => %s", (input, expected) => {
     expect(titleCase(input)).toMatchObject(expected);
   });
+
+  test("is idempotent", () => {
+    expect(titleCase(titleCase("hello world"))).toBe("Hello World");
+  });
 });

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@test/scule.test.ts` around lines 136 - 149, Add an idempotency assertion to
the titleCase test: for each (input, expected) case in the describe("titleCase")
table, after asserting expect(titleCase(input)).toMatchObject(expected), also
assert that calling titleCase again returns the same value (e.g.
expect(titleCase(titleCase(input))).toMatchObject(titleCase(input)) or
toMatchObject(expected)). Update the test block that references titleCase to
include this nested-call check so the function is verified to be idempotent.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@test/scule.test.ts`:
- Around line 136-149: Add an idempotency assertion to the titleCase test: for
each (input, expected) case in the describe("titleCase") table, after asserting
expect(titleCase(input)).toMatchObject(expected), also assert that calling
titleCase again returns the same value (e.g.
expect(titleCase(titleCase(input))).toMatchObject(titleCase(input)) or
toMatchObject(expected)). Update the test block that references titleCase to
include this nested-call check so the function is verified to be idempotent.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 0699c0e2-3c39-41f8-ab14-06093d85bef6

📥 Commits

Reviewing files that changed from the base of the PR and between 5bc6804 and 64693c2.

📒 Files selected for processing (2)

• src/index.ts
• test/scule.test.ts