fix: issue with multiple aliases against same table

[ryaneorth]

With the current implementation of TableExpression#assignAlias you cannot have multiple aliases against the same table. The code block below prevents the second reference from being added to the table alias list.

        if (this.baseExpression.isQueryKeyExpression()){
            QueryKeyExpression qkExpression = ((QueryKeyExpression)this.baseExpression);
            if (qkExpression.getTableAliases() != null && qkExpression.getTableAliases().keyAtValue(table) != null ) {
                return;
            }
        }

Removing the override of assignAlias in TableExpression and deferring to DataExpression's implementation results in the expected behavior.

[rfelcman]

Sorry but during first brief check this PR can't pass due a following reasons:

• It breaks current functionality please check details for EclipseLink PR build / Test on JDK 17 (pull_request) and continuous-integration/jenkins/pr-merge checks.
• For functional fixes/changes like this is good to create some unit test (it's some kind of bug description and avoids regression in the future)

[rfelcman]

About run tests individually it's described at https://github.com/eclipse-ee4j/eclipselink/blob/master/jpa/eclipselink.jpa.testapps/README.md to pass to the IDE command like mvn test -pl :org.eclipse.persistence.jpa.testapps.jpql -Dtest=JUnitJPQLDateTimeTest -Pmysql like in IDEA IteliJ run profiles.
In this PR its about org.eclipse.persistence.core.test module not jpa.
Example command is
mvn test -pl :org.eclipse.persistence.core.test -Pmysql -Dtest=MapCollectionsTestModel -Ddb.platform=org.eclipse.persistence.platform.database.MySQLPlatform -Ddb.driver=com.mysql.cj.jdbc.Driver -Ddb.url=jdbc:mysql://localhost:3306/ecltests?allowPublicKeyRetrieval=true -Ddb.user=root -Ddb.pwd=root
but DB property values depends on Your local environment.

[ryaneorth]

Thank you for your guidance and patience with me on this issue, @rfelcman ! I have implemented a solution that solves the original problem while not leading to regressions. I have also added a test case for the scenario, which fails without the associated change to TableExpression.

[rfelcman]

LGTM

[ryaneorth]

Thank you @rfelcman ! Out of curiosity, when will the next patch release be for 4.x.x?

[rfelcman]

Plan is end of Januray 2023
https://projects.eclipse.org/projects/ee4j.eclipselink/releases/4.0.1
Maven Snapshot based on Nightly build
https://ci.eclipse.org/eclipselink/job/eclipselink-nightly-master/
at
https://jakarta.oss.sonatype.org/content/repositories/snapshots/org/eclipse/persistence/eclipselink/4.0.1-SNAPSHOT/
after 1 hour if all tests will pass