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https://issues.apache.org/jira/browse/TEXT-241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18100210#comment-18100210
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Maksym Korshun commented on TEXT-241:
-------------------------------------
[~ggregory] Hi! Apologies for the empty ticket. I originally created it as a
placeholder while gathering the details and logic fix.
I've updated the ticket description above with the summary. I am currently
working on a patch and unit tests for this and plan to submit a Pull Request
shortly!
> TextStringBuilder.lastIndexOf("") (and deprecated StrBuilder.lastIndexOf(""))
> returns incorrect index (size - 1 instead of size) when searching for an
> empty string.
> --------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: TEXT-241
> URL: https://issues.apache.org/jira/browse/TEXT-241
> Project: Commons Text
> Issue Type: Bug
> Reporter: Maksym Korshun
> Priority: Minor
>
> {{StrBuilder.lastIndexOf(String)}} and
> {{TextStringBuilder.lastIndexOf(String)}}
> do not match {{java.lang.String}} / {{StringBuilder}} for the empty string.
>
> For a builder of length n, {{lastIndexOf("")}} should return n (empty match
> at the end). Both implementations currently return n - 1.
>
> Cause:
> {{lastIndexOf(String, int)}} clamps {{startIndex}} with:
> {{startIndex = startIndex >= size ? size - 1 : startIndex}}
> before the empty-string case, which returns that clamped index. So
> {{lastIndexOf("")}} can never return size.
>
> Example:
>
> {code:java}
> new StrBuilder("abab").lastIndexOf("") // actual 3, expected 4
> "abab".lastIndexOf("") // 4
> new StringBuilder("abab").lastIndexOf("") // 4
> {code}
> Same issue in {{TextStringBuilder}}.
>
> Fix:
> In {{lastIndexOf(String, int)}}, for an empty search string allow the start
> index up to size and return that, keep the existing size - 1 clamp for
> non-empty strings.
>
> Affects:
> - org.apache.commons.text.StrBuilder
> - org.apache.commons.text.TextStringBuilder
>
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