Fixes throwing an exception when 'id' field is present in bib file (#4918)

* Fixes throwing an exception when 'id' field is present in bib file

Fixes #4905

* Remove test for id field

* Renamed ID_FIELD to INTERNAL_ID_FIELD

* Removed unused import

Author: CaptainDaVinci

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

@@ -45,7 +45,7 @@ public class BibEntry implements Cloneable {
     public static final String OBSOLETE_TYPE_HEADER = "bibtextype";
     public static final String KEY_FIELD = "bibtexkey";
     public static final String DEFAULT_TYPE = "misc";
-    protected static final String ID_FIELD = "id";
+    protected static final String INTERNAL_ID_FIELD = "JabRef-internal-id";
     private static final Logger LOGGER = LoggerFactory.getLogger(BibEntry.class);
     private static final Pattern REMOVE_TRAILING_WHITESPACE = Pattern.compile("\\s+$");
     private final SharedBibEntryData sharedBibEntryData;
@@ -161,7 +161,7 @@ public void setId(String id) {
 
         String oldId = this.id;
 
-        eventBus.post(new FieldChangedEvent(this, BibEntry.ID_FIELD, id, oldId));
+        eventBus.post(new FieldChangedEvent(this, BibEntry.INTERNAL_ID_FIELD, id, oldId));
         this.id = id;
         changed = true;
     }
@@ -408,10 +408,6 @@ public Optional<FieldChange> setField(String name, String value, EntryEventSourc
             return Optional.empty();
         }
 
-        if (BibEntry.ID_FIELD.equals(fieldName)) {
-            throw new IllegalArgumentException("The field name '" + name + "' is reserved");
-        }
-
         changed = true;
 
         fields.put(fieldName, value.intern());
@@ -463,10 +459,6 @@ public Optional<FieldChange> clearField(String name) {
     public Optional<FieldChange> clearField(String name, EntryEventSource eventSource) {
         String fieldName = toLowerCase(name);
 
-        if (BibEntry.ID_FIELD.equals(fieldName)) {
-            throw new IllegalArgumentException("The field name '" + name + "' is reserved");
-        }
-
         Optional<String> oldValue = getField(fieldName);
         if (!oldValue.isPresent()) {
             return Optional.empty();

Diff for: src/test/java/org/jabref/model/entry/BibEntryTest.java

@@ -12,7 +12,6 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
-import static org.junit.jupiter.api.Assertions.assertThrows;
 
 public class BibEntryTest {
 
@@ -28,16 +27,6 @@ public void tearDown() {
         entry = null;
     }
 
-    @Test
-    public void notOverrideReservedFields() {
-        assertThrows(IllegalArgumentException.class, () -> entry.setField(BibEntry.ID_FIELD, "somevalue"));
-    }
-
-    @Test
-    public void notClearReservedFields() {
-        assertThrows(IllegalArgumentException.class, () -> entry.clearField(BibEntry.ID_FIELD));
-    }
-
     @Test
     public void getFieldIsCaseInsensitive() throws Exception {
         entry.setField("TeSt", "value");