[jira] [Created] (MNG-8240) ComparableVersion incorrectly handles leading Unicode Nd class zeros

["Matthew Donoughe (Jira)" <ji...@apache.org>]

Matthew Donoughe created MNG-8240:
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             Summary: ComparableVersion incorrectly handles leading Unicode Nd class zeros
                 Key: MNG-8240
                 URL: https://issues.apache.org/jira/browse/MNG-8240
             Project: Maven
          Issue Type: Bug
         Environment: openjdk version "1.8.0_412"
OpenJDK Runtime Environment (Temurin)(build 1.8.0_412-b08)
OpenJDK 64-Bit Server VM (Temurin)(build 25.412-b08, mixed mode)
            Reporter: Matthew Donoughe


ComparableVersion supports positive decimal numbers of unlimited size. As an optimization, the size of the number (in UCS-2 codepoints) determines whether the value should be converted into an int or a long or a BigDecimal. As another optimization, because the size of the value affects the data type, an int is always smaller than a long which is always smaller than a BigDecimal. Leading 0s are removed to avoid the case where 00000000000000000001 > 2.

However, it's specifically '0', DIGIT ZERO, 0x0030, that is being removed. The code that segments the version string into items uses [Character.isDigit|https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/lang/Character.html#isDigit(char)], which uses [Character.getType|https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/lang/Character.html#getType(char)] to check for [DECIMAL_DIGIT_NUMBER|https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/lang/Character.html#DECIMAL_DIGIT_NUMBER] corresponding to the [Unicode Nd class|https://www.fileformat.info/info/unicode/category/Nd/list.htm], and parsing into a number eventually uses [Character.digit|https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/lang/Character.html#digit(char,int)] which likewise supports Unicode Nd class digits. This leads to the following case:
{noformat}
java -jar ~/.m2/repository/org/apache/maven/maven-artifact/3.9.4/maven-artifact-3.9.4.jar ०००००००००००००००००००1 0000000000000000000000002
Display parameters as parsed by Maven (in canonical form and as a list of tokens) and comparison result:
1. ०००००००००००००००००००1 -> 1; tokens: [1]
   ०००००००००००००००००००1 > 0000000000000000000000002
2. 0000000000000000000000002 -> 2; tokens: [2]{noformat}
A 1 with 19 leading zeros is parsed as a BigDecimal, and a 2 with 24 leading zeros is parsed as an int, so therefore 1 > 2. However, the canonicalization still works correctly, so if you canonicalize the versions before comparing them you get 1 < 2 as expected. I don't know if that's better or worse because it can lead to the order being unstable.

I guess the easy solution is to use Character.digit to check for int 0 instead of char '0'.



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