fix suggestion provider for crossref field

src/main/java/org/jabref/gui/LibraryTab.java

@@ -597,8 +597,8 @@ private void setupAutoCompletion() {
         if (autoCompletePreferences.shouldAutoComplete()) {
             suggestionProviders = new SuggestionProviders(getDatabase(), Globals.journalAbbreviationRepository, autoCompletePreferences);
         } else {
-            // Create suggestion providers with database for crossref if auto-completion is deactivated
-            suggestionProviders = new SuggestionProviders(getDatabase());
+            // Create empty suggestion providers if auto-completion is deactivated
+            suggestionProviders = new SuggestionProviders();
         }
         searchAutoCompleter = new PersonNameSuggestionProvider(FieldFactory.getPersonNameFields(), getDatabase());
     }

src/main/java/org/jabref/gui/autocompleter/ContentSelectorSuggestionProvider.java

@@ -1,7 +1,6 @@
 package org.jabref.gui.autocompleter;
 
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.List;
 import java.util.stream.Stream;
 
@@ -26,7 +25,7 @@ public Stream<String> getSource() {
     }
 
     @Override
-    public Collection<String> getPossibleSuggestions() {
+    public List<String> getPossibleSuggestions() {
         List<String> suggestions = new ArrayList<>();
         if (suggestionProvider != null) {
             suggestions.addAll(suggestionProvider.getPossibleSuggestions());

src/main/java/org/jabref/gui/autocompleter/SuggestionProvider.java

@@ -29,6 +29,7 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.List;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -60,7 +61,7 @@ public final Collection<T> provideSuggestions(ISuggestionRequest request) {
 
     protected abstract Equivalence<T> getEquivalence();
 
-    public Collection<T> getPossibleSuggestions() {
+    public List<T> getPossibleSuggestions() {
         Comparator<T> comparator = getComparator().reversed();
         Equivalence<T> equivalence = getEquivalence();
         return getSource().map(equivalence::wrap) // Need to do a bit of acrobatic as there is no distinctBy method

src/main/java/org/jabref/gui/autocompleter/SuggestionProviders.java

@@ -22,21 +22,12 @@ public SuggestionProviders(BibDatabase database, JournalAbbreviationRepository a
         this.isEmpty = false;
     }
 
-    public SuggestionProviders(BibDatabase database) {
-        this.database = database;
-        this.isEmpty = true;
-    }
-
     public SuggestionProviders() {
         this.isEmpty = true;
     }
 
     public SuggestionProvider<?> getForField(Field field) {
         if (isEmpty || !autoCompletePreferences.getCompleteFields().contains(field)) {
-            Set<FieldProperty> fieldProperties = field.getProperties();
-            if (fieldProperties.contains(FieldProperty.SINGLE_ENTRY_LINK)) {
-                return new BibEntrySuggestionProvider(database);
-            }
             return new EmptySuggestionProvider();
         }
 

src/main/java/org/jabref/gui/fieldeditors/FieldEditors.java

@@ -15,7 +15,6 @@
 import org.jabref.logic.integrity.FieldCheckers;
 import org.jabref.logic.journals.JournalAbbreviationRepository;
 import org.jabref.model.database.BibDatabaseContext;
-import org.jabref.model.entry.BibEntry;
 import org.jabref.model.entry.field.Field;
 import org.jabref.model.entry.field.FieldFactory;
 import org.jabref.model.entry.field.FieldProperty;
@@ -90,9 +89,9 @@ public static FieldEditorFX getForField(final Field field,
                 return new OptionEditor<>(new TypeEditorViewModel(field, suggestionProvider, fieldCheckers, undoManager));
             }
         } else if (fieldProperties.contains(FieldProperty.SINGLE_ENTRY_LINK)) {
-            return new LinkedEntriesEditor(field, databaseContext, (SuggestionProvider<BibEntry>) suggestionProvider, fieldCheckers);
+            return new LinkedEntriesEditor(field, databaseContext, suggestionProvider, fieldCheckers);
         } else if (fieldProperties.contains(FieldProperty.MULTIPLE_ENTRY_LINK)) {
-            return new LinkedEntriesEditor(field, databaseContext, (SuggestionProvider<BibEntry>) suggestionProvider, fieldCheckers);
+            return new LinkedEntriesEditor(field, databaseContext, suggestionProvider, fieldCheckers);
         } else if (fieldProperties.contains(FieldProperty.PERSON_NAMES)) {
             return new PersonsEditor(field, suggestionProvider, preferences, fieldCheckers, isMultiLine, undoManager);
         } else if (StandardField.KEYWORDS == field) {

src/main/java/org/jabref/gui/fieldeditors/LinkedEntriesEditor.java

@@ -1,7 +1,6 @@
 package org.jabref.gui.fieldeditors;
 
 import java.util.Comparator;
-import java.util.stream.Collectors;
 
 import javax.swing.undo.UndoManager;
 
@@ -51,21 +50,16 @@ public class LinkedEntriesEditor extends HBox implements FieldEditorFX {
 
     private final LinkedEntriesEditorViewModel viewModel;
 
-    public LinkedEntriesEditor(Field field, BibDatabaseContext databaseContext, SuggestionProvider<BibEntry> suggestionProvider, FieldCheckers fieldCheckers) {
+    public LinkedEntriesEditor(Field field, BibDatabaseContext databaseContext, SuggestionProvider<?> suggestionProvider, FieldCheckers fieldCheckers) {
         ViewLoader.view(this)
                   .root(this)
                   .load();
 
         this.viewModel = new LinkedEntriesEditorViewModel(field, suggestionProvider, databaseContext, fieldCheckers, undoManager);
 
         entryLinkField.setCellFactory(new ViewModelListCellFactory<ParsedEntryLink>().withText(ParsedEntryLink::getKey));
-        // Mind the .collect(Collectors.toList()) as the list needs to be mutable
-        entryLinkField.setSuggestionProvider(request ->
-                suggestionProvider.getPossibleSuggestions().stream()
-                                  .filter(suggestion -> suggestion.getCitationKey().orElse("").toLowerCase()
-                                                                  .contains(request.getUserText().toLowerCase()))
-                                  .map(ParsedEntryLink::new)
-                                  .collect(Collectors.toList()));
+        entryLinkField.setSuggestionProvider(request -> viewModel.getSuggestions(request.getUserText()));
+
         entryLinkField.setTagViewFactory(this::createTag);
         entryLinkField.setConverter(viewModel.getStringConverter());
         entryLinkField.setNewItemProducer(searchText -> viewModel.getStringConverter().fromString(searchText));

src/main/java/org/jabref/gui/fieldeditors/LinkedEntriesEditorViewModel.java

@@ -1,5 +1,9 @@
 package org.jabref.gui.fieldeditors;
 
+import java.util.List;
+import java.util.Locale;
+import java.util.stream.Collectors;
+
 import javax.swing.undo.UndoManager;
 
 import javafx.beans.property.ListProperty;
@@ -11,19 +15,23 @@
 import org.jabref.gui.util.BindingsHelper;
 import org.jabref.logic.integrity.FieldCheckers;
 import org.jabref.model.database.BibDatabaseContext;
+import org.jabref.model.entry.BibEntry;
 import org.jabref.model.entry.EntryLinkList;
 import org.jabref.model.entry.ParsedEntryLink;
 import org.jabref.model.entry.field.Field;
 
 public class LinkedEntriesEditorViewModel extends AbstractEditorViewModel {
 
     private final BibDatabaseContext databaseContext;
+    private final SuggestionProvider<?> suggestionProvider;
     private final ListProperty<ParsedEntryLink> linkedEntries;
 
     public LinkedEntriesEditorViewModel(Field field, SuggestionProvider<?> suggestionProvider, BibDatabaseContext databaseContext, FieldCheckers fieldCheckers, UndoManager undoManager) {
         super(field, suggestionProvider, fieldCheckers, undoManager);
 
         this.databaseContext = databaseContext;
+        this.suggestionProvider = suggestionProvider;
+
         linkedEntries = new SimpleListProperty<>(FXCollections.observableArrayList());
         BindingsHelper.bindContentBidirectional(
                 linkedEntries,
@@ -53,6 +61,24 @@ public ParsedEntryLink fromString(String key) {
         };
     }
 
+    public List<ParsedEntryLink> getSuggestions(String request) {
+        List<ParsedEntryLink> suggestions = suggestionProvider
+                .getPossibleSuggestions()
+                .stream()
+                .map(suggestion -> suggestion instanceof BibEntry bibEntry ? bibEntry.getCitationKey().orElse("") : (String) suggestion)
+                .filter(suggestion -> suggestion.toLowerCase(Locale.ROOT).contains(request.toLowerCase(Locale.ROOT)))
+                .map(suggestion -> new ParsedEntryLink(suggestion, databaseContext.getDatabase()))
+                .distinct()
+                .collect(Collectors.toList());
+
+        ParsedEntryLink requestedLink = new ParsedEntryLink(request, databaseContext.getDatabase());
+        if (!suggestions.contains(requestedLink)) {
+            suggestions.addFirst(requestedLink);
+        }
+
+        return suggestions;
+    }
+
     public void jumpToEntry(ParsedEntryLink parsedEntryLink) {
         // TODO: Implement jump to entry - The implementation can be based on <a href="org.jabref.gui.JabRefFrame.jumpToEntry">JabRefFrame.jumpToEntry</a>
         // TODO: Add toolitp for tag: Localization.lang("Jump to entry")