Sample project to reproduce an issue where textDocument/didOpen triggers for files returned from "Find References", but no corresponding textDocument/didClose triggers. The didClose event does not trigger even after opening the file from the "References" pane and then closing it.

1. Run npm install
2. Create a new workspace folder with some text files:

mkdir /tmp/test-workspace
echo "File 1" > /tmp/test-workspace/file1.txt
echo "File 2" > /tmp/test-workspace/file2.txt
echo "File 3" > /tmp/test-workspace/file3.txt

3. Run debug configuration "Launch Client"
4. Open the workspace folder created in step #2.
5. Open file file1.txt
6. Right-click the word File in file1.txt and "Find References". Notice the errors from file2.txt in the "Problems" pane
7. Opening file2.txt and then closing it will not remove the published diagnostics, nor does clearing it from the References results pane.
8. Closing the original file1.txt will clear the diagnostics for this file.

See bug video here: