In the mentioned method you do basically:
doc.readLock();
try {
   ...
}catch(Exception) {
   resultSet.finish();
}finally{
   doc.readUnlock();
}

this is deadlock prone since the resultSet.finish() may directly attempt to get writeLock() for the document when there
is just one item and the instant substitution is enabled. See the following stacktrace. You shouldn't call the
resultSet.finish() under doc.readLock().

"AWT-EventQueue-2" prio=10 tid=0x087ff400 nid=0x1ecf in Object.wait() [0x85f6b000..0x85f6c1e0]
[ideTestRunner]    java.lang.Thread.State: WAITING (on object monitor)
[ideTestRunner]         at java.lang.Object.wait(Native Method)
[ideTestRunner]         - waiting on <0x8ba55e78> (a org.netbeans.modules.editor.NbEditorDocument)
[ideTestRunner]         at java.lang.Object.wait(Object.java:485)
[ideTestRunner]         at javax.swing.text.AbstractDocument.writeLock(AbstractDocument.java:1329)
[ideTestRunner]         - locked <0x8ba55e78> (a org.netbeans.modules.editor.NbEditorDocument)
[ideTestRunner]         at org.netbeans.editor.BaseDocument.extWriteLock(BaseDocument.java:1368)
[ideTestRunner]         - locked <0x8ba55e78> (a org.netbeans.modules.editor.NbEditorDocument)
[ideTestRunner]         at org.netbeans.editor.BaseDocument.atomicLock(BaseDocument.java:1403)
[ideTestRunner]         - locked <0x8ba55e78> (a org.netbeans.modules.editor.NbEditorDocument)
[ideTestRunner]         at
org.netbeans.editor.ext.html.HTMLCompletionQuery$HTMLResultItem.replaceText(HTMLCompletionQuery.java:545)
[ideTestRunner]         at
org.netbeans.editor.ext.html.HTMLCompletionQuery$TagItem.substituteText(HTMLCompletionQuery.java:771)
[ideTestRunner]         at
org.netbeans.editor.ext.html.HTMLCompletionQuery$HTMLResultItem.defaultAction(HTMLCompletionQuery.java:540)
[ideTestRunner]         at
org.netbeans.editor.ext.html.HTMLCompletionQuery$HTMLResultItem.instantSubstitution(HTMLCompletionQuery.java:514)
[ideTestRunner]         at org.netbeans.modules.editor.completion.CompletionImpl$6.run(CompletionImpl.java:803)
[ideTestRunner]         at org.netbeans.modules.editor.completion.CompletionImpl.runInAWT(CompletionImpl.java:1325)
[ideTestRunner]         at
org.netbeans.modules.editor.completion.CompletionImpl.requestShowCompletionPane(CompletionImpl.java:827)
[ideTestRunner]         at org.netbeans.modules.editor.completion.CompletionImpl.finishNotify(CompletionImpl.java:1245)
[ideTestRunner]         at
org.netbeans.modules.editor.completion.CompletionResultSetImpl.finish(CompletionResultSetImpl.java:235)
[ideTestRunner]         at org.netbeans.spi.editor.completion.CompletionResultSet.finish(CompletionResultSet.java:204)
[ideTestRunner]         at
org.netbeans.modules.languages.features.CompletionProviderImpl$CompletionResult.finish(CompletionProviderImpl.java:521)
[ideTestRunner]         at
org.netbeans.modules.languages.features.CompletionProviderImpl$CompletionTaskImpl.addParserTags(CompletionProviderImpl.java:309)
[ideTestRunner]         at
org.netbeans.modules.languages.features.CompletionProviderImpl$CompletionTaskImpl.compute(CompletionProviderImpl.java:223)
[ideTestRunner]         at
org.netbeans.modules.languages.features.CompletionProviderImpl$CompletionTaskImpl.query(CompletionProviderImpl.java:167)
[ideTestRunner]         at org.netbeans.modules.editor.completion.CompletionImpl.queryResultSets(CompletionImpl.java:1431)
[ideTestRunner]         at org.netbeans.modules.editor.completion.CompletionImpl.completionQuery(CompletionImpl.java:570)
[ideTestRunner]         at org.netbeans.modules.editor.completion.CompletionImpl.showCompletion(CompletionImpl.java:726)
[ideTestRunner]         at org.netbeans.modules.editor.completion.CompletionImpl.access$2200(CompletionImpl.java:76)
[ideTestRunner]         at
org.netbeans.modules.editor.completion.CompletionImpl$CompletionShowAction.actionPerformed(CompletionImpl.java:1351)
[ideTestRunner]         at org.netbeans.modules.editor.completion.CompletionImpl.dispatchKeyEvent(CompletionImpl.java:496)
[ideTestRunner]         at org.netbeans.modules.editor.completion.CompletionImpl.keyPressed(CompletionImpl.java:325)
[ideTestRunner]         at java.awt.AWTEventMulticaster.keyPressed(AWTEventMulticaster.java:233)

...