[test] DerivedSourceSearchParticipantTests.testIndexingInSubPackage failure

at: https://download.eclipse.org/eclipse/downloads/drops4/I20260528-0011/testresults/html/org.eclipse.jdt.core.tests.model_ep440I-unit-linux-x86_64-java21_linux.gtk.x86_64_21.html the following tesorg.eclipse.jdt.core.tests.model.DerivedSourceSearchParticipantTests. testIndexingInSubPackage fails with the following message and ST:

indexDocument should have been called for file in subpackage

junit.framework.AssertionFailedError: indexDocument should have been called for file in subpackage
at junit.framework.Assert.fail(Assert.java:57)
at junit.framework.Assert.assertTrue(Assert.java:22)
at junit.framework.TestCase.assertTrue(TestCase.java:192)
at org.eclipse.jdt.core.tests.model.DerivedSourceSearchParticipantTests.testIndexingInSubPackage(DerivedSourceSearchParticipantTests.java:190)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at junit.framework.TestCase.runTest(TestCase.java:177)
at org.eclipse.jdt.core.tests.junit.extension.TestCase.runTest(TestCase.java:970)
at junit.framework.TestCase.runBare(TestCase.java:142)
at junit.framework.TestResult$1.protect(TestResult.java:122)
at junit.framework.TestResult.runProtected(TestResult.java:142)
at junit.framework.TestResult.run(TestResult.java:125)
at junit.framework.TestCase.run(TestCase.java:130)
at junit.framework.TestSuite.runTest(TestSuite.java:241)
at org.eclipse.jdt.core.tests.model.SuiteOfTestCases$Suite.runTest(SuiteOfTestCases.java:114)
at junit.framework.TestSuite.run(TestSuite.java:236)
at org.eclipse.jdt.core.tests.model.SuiteOfTestCases$Suite.superRun(SuiteOfTestCases.java:97)
at org.eclipse.jdt.core.tests.model.SuiteOfTestCases$Suite$1.protect(SuiteOfTestCases.java:85)
at junit.framework.TestResult.runProtected(TestResult.java:142)
at org.eclipse.jdt.core.tests.model.SuiteOfTestCases$Suite.run(SuiteOfTestCases.java:94)
at junit.framework.TestSuite.runTest(TestSuite.java:241)
at junit.framework.TestSuite.run(TestSuite.java:236)

Refer to issue #4124 for similar reports

Start with DerivedSourceSearchParticipantTests.testIndexingInSubPackage, especially the assertion at line 190, and reproduce the failure from the linked test result. Compare the behavior with issue #4124 and trace why indexDocument is not called for the subpackage file. Done means the test passes and the expected indexing call occurs.

Written by the indexing model from the issue text.