Fix for some Unicode characters in citation keys

src/main/java/org/jabref/model/strings/StringUtil.java

@@ -7,6 +7,7 @@
 import java.io.InputStreamReader;
 import java.net.URL;
 import java.net.URLConnection;
+import java.text.Normalizer;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -587,7 +588,7 @@ public static String limitStringLength(String s, int maxLength) {
      * accept. The basis for replacement is the HashMap UnicodeToReadableCharMap.
      */
     public static String replaceSpecialCharacters(String s) {
-        String result = s;
+        String result = Normalizer.normalize(s, Normalizer.Form.NFC);
         for (Map.Entry<String, String> chrAndReplace : UNICODE_CHAR_MAP.entrySet()) {
             result = result.replace(chrAndReplace.getKey(), chrAndReplace.getValue());
         }

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

@@ -1094,4 +1094,11 @@ void generateKeyCorrectKeyLengthWithAuthNofMthAndUnicode() {
 
         assertEquals(4, generateKey(bibEntry, "[auth4_1]").length());
     }
+
+    @Test
+    void generateKeyWithNonNormalizedUnicode() {
+        BibEntry bibEntry = new BibEntry().withField(StandardField.TITLE, "Modèle et outil pour soutenir la scénarisation pédagogique de MOOC connectivistes");
+
+        assertEquals("Modele", generateKey(bibEntry, "[veryshorttitle]"));
+    }
 }

src/test/java/org/jabref/model/strings/StringUtilTest.java

@@ -299,6 +299,11 @@ void testReplaceSpecialCharacters() {
         assertEquals("aaAeoeeee", StringUtil.replaceSpecialCharacters("åÄöéèë"));
     }
 
+    @Test
+    void replaceSpecialCharactersWithNonNormalizedUnicode() {
+        assertEquals("Modele", StringUtil.replaceSpecialCharacters("Modèle"));
+    }
+
     @Test
     void testRepeatSpaces() {
         assertEquals("", StringUtil.repeatSpaces(0));