reportonlyreachable still fails on optional

[delanym]

I have a plugin that depends on maven-core:3.8.2. Even with the reportonlyreachable flag set true,
https://github.com/GoogleCloudPlatform/cloud-opensource-java/wiki/Linkage-Checker-Enforcer-Rule-Tutorial#reportonlyreachable-flag
the rule fails with

[ERROR] Linkage Checker rule found 3 reachable errors:
Class org.fusesource.jansi.Ansi is not found;
referenced by 2 class files
org.apache.maven.shared.utils.logging.AnsiMessageBuilder (org.apache.maven.shared:maven-shared-utils:3.3.4)
org.apache.maven.shared.utils.logging.Style (org.apache.maven.shared:maven-shared-utils:3.3.4)
Cause:
The valid symbol is in org.fusesource.jansi:jansi:jar:2.2.0 at com.etc:etc-maven-plugin:jar:2.2.0 / org.apache.maven.shared:maven-shared-utils:3.3.4 (compile) / org.fusesource.jansi:jansi:2.2.0 (compile, optional) but it was not selected because the path contains an optional dependency
Class org.fusesource.jansi.AnsiConsole is not found;
referenced by 1 class file
org.apache.maven.shared.utils.logging.MessageUtils (org.apache.maven.shared:maven-shared-utils:3.3.4)
Cause:
The valid symbol is in org.fusesource.jansi:jansi:jar:2.2.0 at com.etc:etc-maven-plugin:jar:2.2.0 / org.apache.maven.shared:maven-shared-utils:3.3.4 (compile) / org.fusesource.jansi:jansi:2.2.0 (compile, optional) but it was not selected because the path contains an optional dependency
Class org.fusesource.jansi.Ansi$Color is not found;
referenced by 1 class file
org.apache.maven.shared.utils.logging.Style (org.apache.maven.shared:maven-shared-utils:3.3.4)
Cause:
The valid symbol is in org.fusesource.jansi:jansi:jar:2.2.0 at com.etc:etc-maven-plugin:jar:2.2.0 / org.apache.maven.shared:maven-shared-utils:3.3.4 (compile) / org.fusesource.jansi:jansi:2.2.0 (compile, optional) but it was not selected because the path contains an optional dependency
Problematic artifacts in the dependency tree:
org.apache.maven.shared:maven-shared-utils:3.3.4 is at:
com.etc:etc-maven-plugin:jar:2.2.0 / org.apache.maven.shared:maven-shared-utils:3.3.4 (compile)

<rules>
  <LinkageCheckerRule implementation="com.google.cloud.tools.dependencies.enforcer.LinkageCheckerRule">
    <level>ERROR</level>
    <reportOnlyReachable>true</reportOnlyReachable>
  <LinkageCheckerRule>
<rules>

linkage-checker-enforcer-rules:1.5.12

[suztomo]

The linkage errors involving optional dependencies are not suppressed by the report-only-reachable flag. If you know these linkage errors are false positives, then you can use an exclusion file to suppress them.

Update: I saw the document of the flag mentioning optional dependencies in the example (org.apache.log.output.jms.JMSQueueTarget and javax.jms.TextMessage) was confusing. I updated the section by removing the sentence. Optional dependencies usually cause the linkage errors but the report-only-reachable does not suppress them.