Add truncate as a BibTex key modifier

src/main/java/org/jabref/logic/formatter/Formatters.java

@@ -29,6 +29,7 @@
 import org.jabref.logic.formatter.casechanger.TitleCaseFormatter;
 import org.jabref.logic.formatter.casechanger.UpperCaseFormatter;
 import org.jabref.logic.formatter.minifier.MinifyNameListFormatter;
+import org.jabref.logic.formatter.minifier.TruncateFormatter;
 import org.jabref.logic.layout.format.LatexToUnicodeFormatter;
 import org.jabref.model.cleanup.Formatter;
 
@@ -102,6 +103,9 @@ public static Optional<Formatter> getFormatterForModifier(String modifier) {
         if (modifier.startsWith(RegexFormatter.KEY)) {
             String regex = modifier.substring(RegexFormatter.KEY.length());
             return Optional.of(new RegexFormatter(regex));
+        } else if (modifier.matches(TruncateFormatter.KEY + "\\d+")) {
+            int truncateAfter = Integer.parseInt(modifier.substring(TruncateFormatter.KEY.length()));
+            return Optional.of(new TruncateFormatter(truncateAfter));
         } else {
             return getAll().stream().filter(f -> f.getKey().equals(modifier)).findAny();
         }

src/main/java/org/jabref/logic/formatter/minifier/TruncateFormatter.java

@@ -0,0 +1,47 @@
+package org.jabref.logic.formatter.minifier;
+
+import org.jabref.logic.l10n.Localization;
+import org.jabref.model.cleanup.Formatter;
+
+public class TruncateFormatter extends Formatter {
+    public static final String KEY = "truncate";
+    private static Integer truncateAfter;
+
+    /**
+     * The TruncateFormatter truncates a string after the given index.
+     *
+     * @param truncateIndex truncate a string after this index.
+     */
+    public TruncateFormatter(int truncateIndex) {
+        truncateAfter = truncateIndex;
+    }
+
+    @Override
+    public String getName() {
+        return Localization.lang("Truncate");
+    }
+
+    @Override
+    public String getKey() {
+        return KEY;
+    }
+
+    /**
+     * Truncates a string after a given index.
+     */
+    @Override
+    public String format(final String input) {
+        final int truncateIndex = Math.min(truncateAfter, input.length());
+        return input.substring(0, truncateIndex).stripTrailing();
+    }
+
+    @Override
+    public String getDescription() {
+        return Localization.lang("Truncates a string after a given index.");
+    }
+
+    @Override
+    public String getExampleInput() {
+        return "Truncate this sentence.";
+    }
+}

src/main/resources/l10n/JabRef_en.properties

@@ -2233,3 +2233,5 @@ Computer\ software.\ The\ standard\ styles\ will\ treat\ this\ entry\ type\ as\
 A\ data\ set\ or\ a\ similar\ collection\ of\ (mostly)\ raw\ data.=A data set or a similar collection of (mostly) raw data.
 
 Display\ count\ of\ items\ in\ group=Display count of items in group
+Truncate=Truncate
+Truncates\ a\ string\ after\ a\ given\ index.=Truncates a string after a given index.

src/test/java/org/jabref/logic/util/BracketedPatternTest.java → src/test/java/org/jabref/logic/bibtexkeypattern/BracketedPatternTest.java

@@ -1,6 +1,5 @@
-package org.jabref.logic.util;
+package org.jabref.logic.bibtexkeypattern;
 
-import org.jabref.logic.bibtexkeypattern.BracketedPattern;
 import org.jabref.model.database.BibDatabase;
 import org.jabref.model.entry.BibEntry;
 import org.jabref.model.entry.BibtexString;
@@ -241,4 +240,43 @@ void regularExpressionReplace() {
         assertEquals("2003-JabRef Science",
                 BracketedPattern.expandBrackets("[year]-[journal:regex(\"Organization\",\"JabRef\")]", ';', dbentry, database));
     }
+
+    /**
+     * Test the [:truncate] modifier
+     */
+    @Test
+    void truncateModifierRemovesTrailingWhitespace() {
+        assertEquals("Open",
+                BracketedPattern.expandBrackets("[fulltitle:truncate5]", ';', dbentry, database));
+    }
+
+    @Test
+    void truncateModifierKeepsIntenalWhitespace() {
+        assertEquals("Open S",
+                BracketedPattern.expandBrackets("[fulltitle:truncate6]", ';', dbentry, database));
+    }
+
+    @Test
+    void truncateModifierWorksWith0Length() {
+        assertEquals("",
+                BracketedPattern.expandBrackets("[fulltitle:truncate0]", ';', dbentry, database));
+    }
+
+    @Test
+    void truncateModifierWorksWith9999Length() {
+        assertEquals("Open Source Software and the \"Private-Collective\" Innovation Model: Issues for Organization Science",
+                BracketedPattern.expandBrackets("[fulltitle:truncate9999]", ';', dbentry, database));
+    }
+
+    @Test
+    void truncateModifiersWorksAppliedTwice() {
+        assertEquals("Open",
+                BracketedPattern.expandBrackets("[fulltitle:truncate6:truncate5]", ';', dbentry, database));
+    }
+
+    @Test
+    void truncateModifierIsIgnoredWithoutAnArgument() {
+        assertEquals("Open Source Software and the \"Private-Collective\" Innovation Model: Issues for Organization Science",
+                BracketedPattern.expandBrackets("[fulltitle:truncate]", ';', dbentry, database));
+    }
 }