Fix convert to bibtex moves contents of the file field (#4123)

* Fix convert to bibtex moves contents of the file field
Fixes #4210
* fix twisted numbers of issue

Author: Siedlerchr

Diff for: CHANGELOG.md

@@ -43,6 +43,7 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 - We reworked the "Edit file" dialog to make it resizeable and improved the workflow for adding and editing files https://github.com/JabRef/jabref/issues/2970
 - We fixed an issue where the month was not shown in the preview https://github.com/JabRef/jabref/issues/3239.
 - Rewritten logic to detect a second jabref instance. [#4023](https://github.com/JabRef/jabref/issues/4023)
+- We fixed an issue where the "Convert to BibTeX-Cleanup" moved the content of the `file` field to the `pdf` field [#4120](https://github.com/JabRef/jabref/issues/4120)
 - We fixed an issue where the preview pane in entry preview in preferences wasn't showing the citation style selected [#3849](https://github.com/JabRef/jabref/issues/3849)
 
 ### Removed

Diff for: src/main/java/org/jabref/model/entry/EntryConverter.java

@@ -25,7 +25,6 @@ public class EntryConverter {
         EntryConverter.FIELD_ALIASES_TEX_TO_LTX.put("archiveprefix", FieldName.EPRINTTYPE);
         EntryConverter.FIELD_ALIASES_TEX_TO_LTX.put(FieldName.JOURNAL, FieldName.JOURNALTITLE);
         EntryConverter.FIELD_ALIASES_TEX_TO_LTX.put(FieldName.KEY, "sortkey");
-        EntryConverter.FIELD_ALIASES_TEX_TO_LTX.put(FieldName.PDF, FieldName.FILE);
         EntryConverter.FIELD_ALIASES_TEX_TO_LTX.put("primaryclass", FieldName.EPRINTCLASS);
         EntryConverter.FIELD_ALIASES_TEX_TO_LTX.put(FieldName.SCHOOL, FieldName.INSTITUTION);
 

Diff for: src/test/java/org/jabref/logic/cleanup/ConvertToBibtexCleanupTest.java

@@ -51,4 +51,14 @@ public void cleanupMovesJournaltitleToJournal() {
         assertEquals(Optional.empty(), entry.getField(FieldName.JOURNALTITLE));
         assertEquals(Optional.of("Best of JabRef"), entry.getField(FieldName.JOURNAL));
     }
+
+    @Test
+    public void cleanUpDoesntMoveFileField() {
+        String fileField = ":Ambriola2006 - On the Systematic Analysis of Natural Language Requirements with CIRCE.pdf:PDF";
+        BibEntry entry = new BibEntry().withField(FieldName.FILE, fileField);
+
+        worker.cleanup(entry);
+
+        assertEquals(Optional.of(fileField), entry.getField(FieldName.FILE));
+    }
 }