Citation keygen: Return vonPart if lastName is empty

CHANGELOG.md

@@ -28,6 +28,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 
 ### Fixed
 
+- We fixed an issue where the author's lastname was not used for the citation key generation if it started with a lowercase letter [#8601](https://github.com/JabRef/jabref/issues/8601)
 - We fixed an issue where custom "Protected terms" files were missing after a restart of JabRef [#8608](https://github.com/JabRef/jabref/issues/8608)
 - We fixed an issue where JabRef could not start due to a missing directory for the fulltex index [#8579](https://github.com/JabRef/jabref/issues/8579)
 - We fixed an issue where long article numbers in the `pages` field would cause an exception and preventing the citation style to display [#8381](https://github.com/JabRef/jabref/issues/8381), [citeproc-java](https://github.com/michel-kraemer/citeproc-java/issues/114)

src/main/java/org/jabref/logic/citationkeypattern/BracketedPattern.java

@@ -711,13 +711,14 @@ private static String keepLettersAndDigitsOnly(String in) {
      * Gets the last name of the first author/editor
      *
      * @param authorList an {@link AuthorList}
-     * @return the surname of an author/editor or "" if no author was found This method is guaranteed to never return
-     * null.
+     * @return the surname of an author/editor or the von part if no lastname is prsent or ""  if no author was found or both firstname+lastname are empty
+     * This method is guaranteed to never return null.
      */
     private static String firstAuthor(AuthorList authorList) {
         return authorList.getAuthors().stream()
                          .findFirst()
-                         .flatMap(Author::getLast).orElse("");
+                         .flatMap(author -> author.getLast().isPresent() ? author.getLast() : author.getVon())
+                         .orElse("");
     }
 
     /**
@@ -967,7 +968,7 @@ private static String authshort(AuthorList authorList) {
         if (numberOfAuthors == 1) {
             author.append(authorList.getAuthor(0).getLast().orElse(""));
         } else if (numberOfAuthors >= 2) {
-            for (int i = 0; i < numberOfAuthors && i < 3; i++) {
+            for (int i = 0; (i < numberOfAuthors) && (i < 3); i++) {
                 author.append(authNofMth(authorList, 1, i + 1));
             }
             if (numberOfAuthors > 3) {
@@ -1004,7 +1005,7 @@ private static String authshort(AuthorList authorList) {
      *                   to "" be returned.
      */
     private static String authIniN(AuthorList authorList, int n) {
-        if (n <= 0 || authorList.isEmpty()) {
+        if ((n <= 0) || authorList.isEmpty()) {
             return "";
         }
 
@@ -1233,7 +1234,7 @@ private static String generateInstitutionKey(String content) {
                 }
             } else if ((tokenTypes.contains(Institution.SCHOOL)
                     || tokenTypes.contains(Institution.DEPARTMENT))
-                    && institutionNameTokens.length > 1) {
+                    && (institutionNameTokens.length > 1)) {
                 // School is an abbreviation of all the words beginning with a
                 // capital letter excluding: department, school and faculty words.
                 StringBuilder schoolSB = new StringBuilder();

src/test/java/org/jabref/logic/citationkeypattern/CitationKeyGeneratorTest.java

@@ -1134,4 +1134,18 @@ void generateKeyWithFallbackField() {
 
         assertEquals("2021", generateKey(bibEntry, "[title:([EPRINT:([YEAR])])]"));
     }
+
+    @Test
+    void generateKeyWithLowercaseAuthorLastnameUseVonPart() {
+        BibEntry entry = createABibEntryAuthor("Stéphane d'Ascoli");
+        entry.setField(StandardField.YEAR, "2021");
+        assertEquals("dAscoli2021", generateKey(entry, "[auth][year]"));
+    }
+
+    @Test
+    void generateKeyWithLowercaseAuthorWithVonAndLastname() {
+        BibEntry entry = createABibEntryAuthor("Michiel van den Brekel");
+        entry.setField(StandardField.YEAR, "2021");
+        assertEquals("Brekel2021", generateKey(entry, "[auth][year]"));
+    }
 }