When loading configuration from data config file, variable substitution does not work for "solr.core.instanceDir"

[szhou1998]

I'm running into an issue where variable substitution is not working properly when loading data config from an XML file. I have an entity element with attribute url="${solr.core.instanceDir}/workDir/claimcontact.xml". When running full-import, I get this error:

"level":"ERROR","loggerName":"org.apache.solr.handler.dataimport.DocBuilder",
"Exception while processing: claimcontact document : SolrInputDocument(fields: [])"
"org.apache.solr.handler.dataimport.DataImportHandlerException: 
java.security.AccessControlException: access denied ("java.io.FilePermission" "/workDir/claimcontact.xml" "read")"

"java.security.AccessControlContext","method":"checkPermission","file":"AccessControlContext.java","line":472
"java.security.AccessController","method":"checkPermission","file":"AccessController.java","line":897
"java.lang.SecurityManager","method":"checkPermission","file":"SecurityManager.java","line":322
"java.lang.SecurityManager","method":"checkRead","file":"SecurityManager.java","line":661
"java.io.File","method":"isFile","file":"File.java","line":889
"org.apache.solr.handler.dataimport.FileDataSource","method":"getFile","file":"FileDataSource.java","line":119
"org.apache.solr.handler.dataimport.FileDataSource","method":"getData","file":"FileDataSource.java","line":86
"org.apache.solr.handler.dataimport.FileDataSource","method":"getData","file":"FileDataSource.java","line":48
"org.apache.solr.handler.dataimport.XPathEntityProcessor","method":"initQuery","file":"XPathEntityProcessor.java","line":291
"org.apache.solr.handler.dataimport.DataImportHandlerException","method":"wrapAndThrow","file":"DataImportHandlerException.java","line":61
"org.apache.solr.handler.dataimport.XPathEntityProcessor","method":"initQuery","file":"XPathEntityProcessor.java","line":294
"org.apache.solr.handler.dataimport.XPathEntityProcessor","method":"fetchNextRow","file":"XPathEntityProcessor.java","line":232
"org.apache.solr.handler.dataimport.XPathEntityProcessor","method":"nextRow","file":"XPathEntityProcessor.java","line":212
"org.apache.solr.handler.dataimport.EntityProcessorWrapper","method":"nextRow","file":"EntityProcessorWrapper.java","line":267
"org.apache.solr.handler.dataimport.DocBuilder","method":"buildDocument","file":"DocBuilder.java","line":494
"org.apache.solr.handler.dataimport.DocBuilder","method":"buildDocument","file":"DocBuilder.java","line":433
"org.apache.solr.handler.dataimport.DocBuilder","method":"doFullDump","file":"DocBuilder.java","line":348
"org.apache.solr.handler.dataimport.DocBuilder","method":"execute","file":"DocBuilder.java","line":236
"org.apache.solr.handler.dataimport.DataImporter","method":"doFullImport","file":"DataImporter.java","line":424
"org.apache.solr.handler.dataimport.DataImporter","method":"runCmd","file":"DataImporter.java","line":483
"org.apache.solr.handler.dataimport.DataImporter","method":"lambda$runAsync$0","file":"DataImporter.java","line":466

As you can see, the solr.core.instanceDir variable is not being substituted correctly. I believe the issue is with this bit of code in DocBuilder:
https://github.com/SearchScale/dataimporthandler/blob/branch_9x/src/main/java/org/apache/solr/handler/dataimport/DocBuilder.java#L116-L120

In Solr 8, a change was made to get the properties from CoreDescriptor substitutableProperties: apache/lucene-solr@17ae79b#diff-9eadac54fe1ace540cb05b6711791be03a9289a7d6f16615fb4efa4ee31641f9

CoreDescriptor substitutableProperties has solr.core.instanceDir as a property: https://github.com/apache/solr/blob/main/solr/core/src/java/org/apache/solr/core/CoreDescriptor.java#L269

However, note that in the Solr 9 DocBuilder change in this repo, the Solr 8 "before" code did not have this change: ec730d5#diff-88595e01694c11981cecf4b71fdc54969870ff49737208856685388eb3bb0ee5

Should this be changed to new VariableResolver(dataImporter.getCore().getCoreDescriptor().getSubstitutableProperties());?