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https://issues.apache.org/jira/browse/MNG-8241?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Elliotte Rusty Harold resolved MNG-8241.
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Fix Version/s: 4.0.0-rc-4
Resolution: Fixed
> ComparableVersion incorrectly handles Unicode non-BMP characters
> ----------------------------------------------------------------
>
> Key: MNG-8241
> URL: https://issues.apache.org/jira/browse/MNG-8241
> Project: Maven
> Issue Type: Bug
> Reporter: Matthew Donoughe
> Assignee: Elliotte Rusty Harold
> Priority: Minor
> Fix For: 4.0.0-rc-4
>
>
> Java strings are (usually) Unicode, but Java chars are a subset of Unicode.
> ComparableVersion makes heavy use of
> [String.charAt|https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/lang/String.html#charAt(int)],
> which will return surrogate values instead of Unicode code points whenever a
> character takes more than 16 bits.
> This leads to the following behavior:
>
> {noformat}
> java -jar
> ~/.m2/repository/org/apache/maven/maven-artifact/3.9.4/maven-artifact-3.9.4.jar
> 1 𝟤
> Display parameters as parsed by Maven (in canonical form and as a list of
> tokens) and comparison result:
> 1. 1 -> 1; tokens: [1]
> 1 > 𝟤
> 2. 𝟤 -> 𝟤; tokens: [𝟤]{noformat}
> 1 (DIGIT ONE) > 𝟤 (MATHEMATICAL SANS-SERIF DIGIT TWO) because
> ComparableVersion sees 𝟤 as two invalid characters and treats it as text.
>
>
> {noformat}
> java -jar
> ~/.m2/repository/org/apache/maven/maven-artifact/3.9.4/maven-artifact-3.9.4.jar
> 0 𝟤
> Display parameters as parsed by Maven (in canonical form and as a list of
> tokens) and comparison result:
> 1. 0 -> ; tokens: []
> 0 < 𝟤
> 2. 𝟤 -> 𝟤; tokens: [𝟤]{noformat}
> However, 0 (DIGIT 0) is still < 𝟤 (MATHEMATICAL SANS-SERIF DIGIT TWO). 0 < 𝟤
> < 1 the same way 0 < a < 1.
>
> It's unclear whether this should be considered to be a bug or whether it's
> just an undocumented limitation. String.charAt and String.length should be
> avoided unless you can be sure the characters are all BMP (Basic Multilingual
> Plane).
> I was initially worried that 𝟣𝟣𝟣𝟣𝟣 (MATHEMATICAL SANS-SERIF DIGIT ONE) >
> 22222 (DIGIT TWO) because "𝟣𝟣𝟣𝟣𝟣".length is 10, greater than
> MAX_INTITEM_LENGTH, but that code doesn't even get hit because String.charAt
> is producing effectively "�����������". If the code is changed to identify
> non-BMP Nd class digits like 𝟣 as digits then the code that determines the
> required size of the data type needs to be updated to measure the length in
> code points instead of chars.
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