Fix: fallback conversion from BibTeX year field to biblatex date field (#13040)

* Add fallback logic to ConvertToBiblatexCleanup for parsing ISO-style dates in BibTeX `year` field

* Add fallback logic to ConvertToBiblatexCleanup for parsing ISO-style dates in BibTeX `year` field

* Add changelog entry

* changelog

* test: replace setField with withField

* apply suggestions for concise changelog and remove redundant trim in ConvertToBiblatexCleanup

* use List instead of Collection in applyDateFallback

* use hasField for date check

* fix: Trim input in Date.parse and apply style review feedback #13040

* fix: Trim input in Date.parse and apply style review feedback #13040

Author: wanling0000

CHANGELOG.md

@@ -19,6 +19,7 @@ Note that this project **does not** adhere to [Semantic Versioning](https://semv
 
 ### Fixed
 
+- We added a fallback for the "Convert to biblatex" cleanup when it failed to populate the `date` field if `year` contained a full date in ISO format (e.g., `2011-11-11`). [#11868](https://github.com/JabRef/jabref/issues/11868)
 - We fixed an issue where directory check for relative path was not handled properly under library properties. [#13017](https://github.com/JabRef/jabref/issues/13017)
 - We fixed an issue where the option for which method to use when parsing plaintext citations was unavailable in the 'Create New Entry' tool. [#8808](https://github.com/JabRef/jabref/issues/8808)
 

jablib/src/main/java/org/jabref/logic/cleanup/ConvertToBiblatexCleanup.java

@@ -53,6 +53,30 @@ public List<FieldChange> cleanup(BibEntry entry) {
                 }
             });
         }
+        // If still no 'date' field, try fallback logic
+        if (!entry.hasField(StandardField.DATE)) {
+            changes.addAll(applyDateFallback(entry));
+        }
+
+        return changes;
+    }
+
+    private List<FieldChange> applyDateFallback(BibEntry entry) {
+        Optional<String> yearValue = entry.getFieldOrAlias(StandardField.YEAR);
+        if (yearValue.isEmpty()) {
+            return List.of();
+        }
+
+        String yearText = yearValue.get();
+        if (Date.parse(yearText).isEmpty()) {
+            return List.of();
+        }
+
+        List<FieldChange> changes = new ArrayList<>();
+        // If year was a full date, move it from year to date field.
+        entry.setField(StandardField.DATE, yearText).ifPresent(changes::add);
+        entry.clearField(StandardField.YEAR).ifPresent(changes::add);
+
         return changes;
     }
 }

jablib/src/main/java/org/jabref/model/entry/Date.java

@@ -130,6 +130,8 @@ public Date(TemporalAccessor date, Season season) {
     public static Optional<Date> parse(String dateString) {
         Objects.requireNonNull(dateString);
 
+        dateString = dateString.strip();
+
         if (dateString.isEmpty()) {
             return Optional.empty();
         }

jablib/src/test/java/org/jabref/logic/cleanup/ConvertToBiblatexCleanupTest.java

@@ -7,6 +7,8 @@
 
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
@@ -97,4 +99,22 @@ void cleanupMovesJournalToJournaltitle() {
         assertEquals(Optional.empty(), entry.getField(StandardField.JOURNAL));
         assertEquals(Optional.of("Best of JabRef"), entry.getField(StandardField.JOURNALTITLE));
     }
+
+    @ParameterizedTest
+    @ValueSource(strings = {
+            "2011-11",
+            "2011-11-11",
+            "2010/2011",
+            "0030 BC",
+            "-0876",
+            "2004-22"
+    })
+    void fallbackDateParsing_shouldAcceptTypicalBibLatexValues(String fakeYear) {
+        BibEntry entry = new BibEntry().withField(StandardField.YEAR, fakeYear);
+
+        worker.cleanup(entry);
+
+        assertEquals(Optional.of(fakeYear), entry.getField(StandardField.DATE));
+        assertEquals(Optional.empty(), entry.getField(StandardField.YEAR));
+    }
 }

jablib/src/test/java/org/jabref/model/entry/DateTest.java

@@ -123,4 +123,13 @@ void parseZonedTime() {
     void parseDateNull() {
         assertThrows(NullPointerException.class, () -> Date.parse(null));
     }
+
+    // Date.parse() has been updated to defensively strip surrounding whitespace from input strings.
+    @Test
+    void parseShouldTrimValidDate() {
+        assertEquals(
+                Date.parse("2025-05-02"),
+                Date.parse(" 2025-05-02 ")
+        );
+    }
 }