Fix NoSuchElementException in ThreeWayMerge dialog

CHANGELOG.md

@@ -89,6 +89,7 @@ Note that this project **does not** adhere to [Semantic Versioning](https://semv
 - We fixed an issue where the tab showing the fulltext search results would appear blank after switching library. [#13241](https://github.com/JabRef/jabref/issues/13241)
 - We fixed an issue where the groups were still displayed after closing all libraries. [#13382](https://github.com/JabRef/jabref/issues/13382)
 - Enhanced field selection logic in the Merge Entries dialog when fetching from DOI to prefer valid years and entry types. [#12549](https://github.com/JabRef/jabref/issues/12549)
+- We fixed an issue where opening the ThreewayMerge dialog would throw an exception when one of the two year fields dos not contain a year. [#13673](https://github.com/JabRef/jabref/issues/13673)
 
 ### Removed
 

jabgui/src/test/java/org/jabref/gui/mergeentries/FieldRowViewModelTest.java

@@ -224,14 +224,23 @@ void newYearShouldBeSelectedForYearsWithLargeValueGap() {
     }
 
     @Test
-    void yearInRangeShouldBeSelected() {
+    void selectRightYearWhenInRange() {
         BibEntry leftEntry = new BibEntry().withField(StandardField.YEAR, "1700");
         BibEntry rightEntry = new BibEntry().withField(StandardField.YEAR, "2000");
         FieldRowViewModel yearField = new FieldRowViewModel(StandardField.YEAR, leftEntry, rightEntry, mergedEntry, fieldMergerFactory);
         yearField.autoSelectBetterValue();
         assertEquals(FieldRowViewModel.Selection.RIGHT, yearField.getSelection());
     }
 
+    @Test
+    void selectLeftYearWhenInRange() {
+        BibEntry leftEntry = new BibEntry().withField(StandardField.YEAR, "2005");
+        BibEntry rightEntry = new BibEntry().withField(StandardField.YEAR, "1700");
+        FieldRowViewModel yearField = new FieldRowViewModel(StandardField.YEAR, leftEntry, rightEntry, mergedEntry, fieldMergerFactory);
+        yearField.autoSelectBetterValue();
+        assertEquals(FieldRowViewModel.Selection.LEFT, yearField.getSelection());
+    }
+
     public FieldRowViewModel createViewModelForField(Field field) {
         return new FieldRowViewModel(field, leftEntry, rightEntry, mergedEntry, fieldMergerFactory);
     }

jablib/src/main/java/org/jabref/logic/bibtex/comparator/YearFieldValuePlausibilityComparator.java

@@ -6,6 +6,7 @@
 import java.util.regex.Pattern;
 
 import org.jabref.logic.integrity.YearChecker;
+import org.jabref.model.strings.StringUtil;
 
 public class YearFieldValuePlausibilityComparator extends FieldValuePlausibilityComparator {
 
@@ -21,28 +22,50 @@ public class YearFieldValuePlausibilityComparator extends FieldValuePlausibility
 
     @Override
     public ComparisonResult compare(String leftValue, String rightValue) {
-        YearChecker checker = new YearChecker();
+        boolean isLeftBlank = StringUtil.isBlank(leftValue);
+        boolean isRightBlank = StringUtil.isBlank(rightValue);
+        if (isLeftBlank && !isRightBlank) {
+            return ComparisonResult.RIGHT_BETTER;
+        } else if (isRightBlank && !isLeftBlank) {
+            return ComparisonResult.LEFT_BETTER;
+        } else if (isLeftBlank && isRightBlank) {
+            return ComparisonResult.UNDETERMINED;
+        }
 
-        boolean leftValid = checker.checkValue(leftValue).isEmpty();
+        // left and right values are not blank.
 
-        if (leftValid) {
-            Optional<Integer> leftYear = extractYear(leftValue);
-            Optional<Integer> rightYear = extractYear(rightValue);
+        boolean leftValueCorrectlyFormatted = YearChecker.isValueCorrectlyFormatted(leftValue);
+        boolean rightValueCorrectlyFormatted = YearChecker.isValueCorrectlyFormatted(rightValue);
+        if (leftValueCorrectlyFormatted && !rightValueCorrectlyFormatted) {
+            return ComparisonResult.LEFT_BETTER;
+        } else if (rightValueCorrectlyFormatted && !leftValueCorrectlyFormatted) {
+            return ComparisonResult.RIGHT_BETTER;
+        } else if (!leftValueCorrectlyFormatted && !rightValueCorrectlyFormatted) {
+            return ComparisonResult.UNDETERMINED;
+        }
 
-            boolean leftYearInRange = (leftYear.get() >= 1800) && (leftYear.get() <= Year.now().getValue() + 2);
+        // left and right values are correctly formatted.
 
-            if (leftYearInRange) {
-                int diff = Math.abs(leftYear.get() - rightYear.get());
-                if (diff > 10) {
-                    return rightYear.get() > leftYear.get()
-                            ? ComparisonResult.RIGHT_BETTER
-                            : ComparisonResult.LEFT_BETTER;
-                }
-                return ComparisonResult.UNDETERMINED; // years are close, undetermined
-            }
+        Integer leftYear = extractYear(leftValue).get();
+        Integer rightYear = extractYear(rightValue).get();
+        boolean leftYearInRange = (leftYear >= 1800) && (leftYear <= Year.now().getValue() + 2);
+        boolean rightYearInRange = (rightYear >= 1800) && (rightYear <= Year.now().getValue() + 2);
+        if (leftYearInRange && !rightYearInRange) {
+            return ComparisonResult.LEFT_BETTER;
+        } else if (rightYearInRange && !leftYearInRange) {
             return ComparisonResult.RIGHT_BETTER;
-            }
-        return ComparisonResult.RIGHT_BETTER;
+        } else if (!leftYearInRange && !rightYearInRange) {
+            return ComparisonResult.UNDETERMINED;
+        }
+
+        int diff = Math.abs(leftYear - rightYear);
+        if (diff > 10) {
+            return rightYear > leftYear
+                    ? ComparisonResult.RIGHT_BETTER
+                    : ComparisonResult.LEFT_BETTER;
+        }
+
+        return ComparisonResult.UNDETERMINED; // years are close, undetermined
     }
 
     /**

jablib/src/main/java/org/jabref/logic/integrity/YearChecker.java

@@ -9,8 +9,7 @@
 
 public class YearChecker implements ValueChecker {
 
-    private static final Predicate<String> CONTAINS_FOUR_DIGIT = Pattern.compile("([^0-9]|^)[0-9]{4}([^0-9]|$)")
-                                                                        .asPredicate();
+    private static final Predicate<String> CONTAINS_FOUR_DIGIT = Pattern.compile("([^0-9]|^)[0-9]{4}([^0-9]|$)").asPredicate();
     private static final Predicate<String> ENDS_WITH_FOUR_DIGIT = Pattern.compile("[0-9]{4}$").asPredicate();
     private static final String PUNCTUATION_MARKS = "[(){},.;!?<>%&$]";
 
@@ -37,4 +36,20 @@ public Optional<String> checkValue(String value) {
 
         return Optional.empty();
     }
+
+    public static boolean isValueCorrectlyFormatted(String value) {
+        if (StringUtil.isBlank(value)) {
+            return false;
+        }
+
+        if (!CONTAINS_FOUR_DIGIT.test(value.trim())) {
+            return false;
+        }
+
+        if (!ENDS_WITH_FOUR_DIGIT.test(value.replaceAll(PUNCTUATION_MARKS, ""))) {
+            return false;
+        }
+
+        return true;
+    }
 }