Add date checker

CHANGELOG.md

@@ -11,6 +11,7 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 ## [Unreleased]
 
 ### Changed
+- We added a validity check for dates in the `date` and `urldate` fields.
 - We added a text file export for 'Find Unlinked Files'. [#3341](https://github.com/JabRef/jabref/issues/3341)
 - We added a fetcher based on RFC-IDs. [#3971](https://github.com/JabRef/jabref/issues/3971)
 - We changed the implementation of the `[shorttitle]` key pattern. It now removes small words like `a`, `an`, `on`, `the` etc. Refer to the help page for a complete overview. [Feature request in the forum](http://discourse.jabref.org/t/jabref-differences-in-shorttitle-between-versions-3-8-1-and-4-not-discounting-the-a-an-of-in-titles/1147)

src/main/java/org/jabref/logic/integrity/DateChecker.java

@@ -0,0 +1,24 @@
+package org.jabref.logic.integrity;
+
+import java.util.Optional;
+
+import org.jabref.logic.l10n.Localization;
+import org.jabref.model.entry.Date;
+import org.jabref.model.strings.StringUtil;
+
+public class DateChecker implements ValueChecker {
+
+    @Override
+    public Optional<String> checkValue(String value) {
+        if (StringUtil.isBlank(value)) {
+            return Optional.empty();
+        }
+
+        Optional<Date> parsedDate = Date.parse(value);
+        if (!parsedDate.isPresent()) {
+            return Optional.of(Localization.lang("incorrect format"));
+        }
+
+        return Optional.empty();
+    }
+}

src/main/java/org/jabref/logic/integrity/FieldCheckers.java

@@ -50,6 +50,13 @@ private static Multimap<String, ValueChecker> getAllMap(BibDatabaseContext datab
         fieldCheckers.put(FieldName.YEAR, new YearChecker());
         fieldCheckers.put(FieldName.KEY, new ValidBibtexKeyChecker(enforceLegalKey));
 
+        if (databaseContext.isBiblatexMode()) {
+            fieldCheckers.put(FieldName.DATE, new DateChecker());
+            fieldCheckers.put(FieldName.URLDATE, new DateChecker());
+            fieldCheckers.put(FieldName.EVENTDATE, new DateChecker());
+            fieldCheckers.put(FieldName.ORIGDATE, new DateChecker());
+        }
+
         return fieldCheckers;
     }
 

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

@@ -44,9 +44,17 @@ public Date(TemporalAccessor date) {
      */
     public static Optional<Date> parse(String dateString) {
         Objects.requireNonNull(dateString);
-        List<String> formatStrings = Arrays.asList("uuuu-M-d", "uuuu-M", "d-M-uuuu", "M/uu", "M/uuuu", "MMMM d, uuuu",
+        List<String> formatStrings = Arrays.asList(
+                "uuuu-M-d",
+                "uuuu-M",
+                "d-M-uuuu",
+                "M-uuuu",
+                "M/uu",
+                "M/uuuu",
+                "MMMM d, uuuu",
                 "MMMM, uuuu",
-                "d.M.uuuu", "uuuu.M.d", "uuuu");
+                "d.M.uuuu",
+                "uuuu.M.d", "uuuu");
 
             for (String formatString : formatStrings) {
                 try {

src/test/java/org/jabref/logic/integrity/DateCheckerTest.java

@@ -0,0 +1,28 @@
+package org.jabref.logic.integrity;
+
+import java.util.Optional;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class DateCheckerTest {
+
+    private DateChecker checker;
+
+    @BeforeEach
+    void setUp() {
+        checker = new DateChecker();
+    }
+
+    @Test
+    void complainsAboutInvalidIsoLikeDate() {
+        assertEquals(Optional.of("incorrect format"), checker.checkValue("2018-04-21TZ"));
+    }
+
+    @Test
+    void acceptsValidIsoDate() {
+        assertEquals(Optional.empty(), checker.checkValue("2018-04-21"));
+    }
+}

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

@@ -1,22 +1,43 @@
 package org.jabref.model.entry;
 
 import java.time.LocalDate;
+import java.time.Year;
+import java.time.YearMonth;
 import java.util.Optional;
 
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
-public class DateTest {
+class DateTest {
 
     @Test
-    public void parseCorrectlyDayMonthYearDate() throws Exception {
+    void parseCorrectlyDayMonthYearDate() throws Exception {
         Date expected = new Date(LocalDate.of(2014, 6, 19));
         assertEquals(Optional.of(expected), Date.parse("19-06-2014"));
     }
 
-    public void parseDateNull() {
-        assertThrows(NullPointerException.class, () -> assertEquals(Optional.empty(), Date.parse(null)));
+    @Test
+    void parseCorrectlyMonthYearDate() throws Exception {
+        Date expected = new Date(YearMonth.of(2014, 6));
+        assertEquals(Optional.of(expected), Date.parse("06-2014"));
+    }
+
+    @Test
+    void parseCorrectlyYearMonthDate() throws Exception {
+        Date expected = new Date(YearMonth.of(2014, 6));
+        assertEquals(Optional.of(expected), Date.parse("2014-06"));
+    }
+
+    @Test
+    void parseCorrectlyYearDate() throws Exception {
+        Date expected = new Date(Year.of(2014));
+        assertEquals(Optional.of(expected), Date.parse("2014"));
+    }
+
+    @Test
+    void parseDateNull() {
+        assertThrows(NullPointerException.class, () -> Date.parse(null));
     }
 }