fix(string): split and then join should be identity

[peter-jerry-ye]

Fixes #2019

[peter-jerry-ye-code-review]

Fixed inconsistent handling of empty strings in split operation

Category
Correctness
Code Snippet
string/methods.mbt:664-670
if view.is_empty() {
IterContinue
} else {
yield_(view)
}
-> yield_(view)
Recommendation
The change to always yield the view is correct. This ensures consistent behavior with empty strings and trailing separators.
Reasoning
The previous implementation was incorrectly skipping empty strings, which made operations like split-join roundtrip impossible. The new behavior properly preserves empty segments, which is the expected behavior in string splitting operations.

Added comprehensive split-join roundtrip test cases

Category
Maintainability
Code Snippet
string/string_test.mbt:714-728
test "split and then join should be identity" {
...
}
Recommendation
Consider adding more test cases with different Unicode sequences and multi-character separators
Reasoning
While the current test cases cover basic scenarios well, adding more complex cases would help ensure the implementation remains correct for edge cases involving Unicode and multi-character separators

Duplicate test cases in string_test.mbt

Category
Maintainability
Code Snippet
string/string_test.mbt:394-401 and 482-489
Recommendation
Remove the duplicated test blocks or extract common test cases into a shared function
Reasoning
The file contains identical test blocks which increases maintenance burden and could lead to inconsistencies if only one copy is updated

[coveralls]

Pull Request Test Coverage Report for Build 6573

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 92.4%

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Totals
Change from base Build 6572:	0.01%
Covered Lines:	6140
Relevant Lines:	6645

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💛 - Coveralls

[tonyfettes]

LGTM