Fixes bugs in the regex cite key pattern modifier

src/main/java/org/jabref/logic/formatter/bibtexfields/RegexFormatter.java

@@ -5,41 +5,56 @@
 import java.util.Objects;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+import java.util.regex.PatternSyntaxException;
 
 import org.jabref.logic.cleanup.Formatter;
 import org.jabref.logic.l10n.Localization;
 
-public class RegexFormatter extends Formatter {
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
+public class RegexFormatter extends Formatter {
     public static final String KEY = "regex";
+    private static final Logger LOGGER = LoggerFactory.getLogger(RegexFormatter.class);
     private static final Pattern PATTERN_ESCAPED_OPENING_CURLY_BRACE = Pattern.compile("\\\\\\{");
     private static final Pattern PATTERN_ESCAPED_CLOSING_CURLY_BRACE = Pattern.compile("\\\\\\}");
     // RegEx to match {...}
     // \\ is required to have the { interpreted as character
     // ? is required to disable the aggressive match
     private static final Pattern PATTERN_ENCLOSED_IN_CURLY_BRACES = Pattern.compile("(\\{.*?})");
+    private static final String REGEX_CAPTURING_GROUP = "regex";
+    private static final String REPLACEMENT_CAPTURING_GROUP = "replacement";
+    /**
+     * Matches a valid argument to the constructor. Two capturing groups are used to parse the {@link
+     * RegexFormatter#regex} and {@link RegexFormatter#replacement} used in {@link RegexFormatter#format(String)}
+     */
+    private static final Pattern CONSTRUCTOR_ARGUMENT = Pattern.compile(
+            "^\\(\"(?<" + REGEX_CAPTURING_GROUP + ">.*?)\" *?, *?\"(?<" + REPLACEMENT_CAPTURING_GROUP + ">.*)\"\\)$");
     // Magic arbitrary unicode char, which will never appear in bibtex files
     private static final String PLACEHOLDER_FOR_PROTECTED_GROUP = Character.toString('\u0A14');
     private static final String PLACEHOLDER_FOR_OPENING_CURLY_BRACE = Character.toString('\u0A15');
     private static final String PLACEHOLDER_FOR_CLOSING_CURLY_BRACE = Character.toString('\u0A16');
-    private static final String QUOTE_AND_OPENING_BRACE = "\"(";
-    private static final int LENGTH_OF_QUOTE_AND_OPENING_BRACE = QUOTE_AND_OPENING_BRACE.length();
-    private static final String CLOSING_BRACE_AND_QUOTE = ")\"";
-    private static final int LENGTH_OF_CLOSING_BRACE_AND_QUOTE = CLOSING_BRACE_AND_QUOTE.length();
-    private static String regex;
-    private String replacement;
+    private final String regex;
+    private final String replacement;
 
     /**
      * Constructs a new regular expression-based formatter with the given RegEx.
      *
-     * @param input the regular expressions for matching and replacing given in the form {@code (<regex>, <replace>)}.
+     * @param input the regular expressions for matching and replacing given in the form {@code ("<regex>",
+     *              "<replace>")}.
      */
     public RegexFormatter(String input) {
-        // formatting is like ("exp1","exp2"), we want to first remove (" and ")
-        String rexToSet = input.substring(LENGTH_OF_QUOTE_AND_OPENING_BRACE, input.length() - LENGTH_OF_CLOSING_BRACE_AND_QUOTE);
-        String[] parts = rexToSet.split("\",\"");
-        regex = parts[0];
-        replacement = parts[1];
+        Objects.requireNonNull(input);
+        input = input.trim();
+        Matcher constructorArgument = CONSTRUCTOR_ARGUMENT.matcher(input);
+        if (constructorArgument.matches()) {
+            regex = constructorArgument.group(REGEX_CAPTURING_GROUP);
+            replacement = constructorArgument.group(REPLACEMENT_CAPTURING_GROUP);
+        } else {
+            regex = null;
+            replacement = null;
+            LOGGER.warn("RegexFormatter could not parse the input: " + input);
+        }
     }
 
     @Override
@@ -60,7 +75,13 @@ private String replaceHonoringProtectedGroups(final String input) {
             replaced.add(matcher.group(1));
         }
         String workingString = matcher.replaceAll(PLACEHOLDER_FOR_PROTECTED_GROUP);
-        workingString = workingString.replaceAll(regex, replacement);
+        try {
+            workingString = workingString.replaceAll(regex, replacement);
+        } catch (PatternSyntaxException e) {
+            LOGGER.warn("There is a syntax error in the regular expression, " +
+                    regex + ", used by the regex modifier", e);
+            return input;
+        }
 
         for (String r : replaced) {
             workingString = workingString.replaceFirst(PLACEHOLDER_FOR_PROTECTED_GROUP, r);
@@ -71,7 +92,7 @@ private String replaceHonoringProtectedGroups(final String input) {
     @Override
     public String format(final String input) {
         Objects.requireNonNull(input);
-        if (regex == null) {
+        if (regex == null || replacement == null) {
             return input;
         }
 

src/test/java/org/jabref/logic/formatter/bibtexfields/RegexFormatterTest.java

@@ -4,9 +4,6 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
-/**
- * Tests in addition to the general tests from {@link org.jabref.logic.formatter.FormatterTest}
- */
 class RegexFormatterTest {
 
     private RegexFormatter formatter;
@@ -52,4 +49,28 @@ void formatExample() {
         formatter = new RegexFormatter("(\" \",\"-\")");
         assertEquals("Please-replace-the-spaces", formatter.format(formatter.getExampleInput()));
     }
+
+    @Test
+    void formatCanRemoveMatchesWithEmptyReplacement() {
+        formatter = new RegexFormatter("(\"[A-Z]\",\"\")");
+        assertEquals("abc", formatter.format("AaBbCc"));
+    }
+
+    @Test
+    void constructorWithInvalidConstructorArgumentReturnUnchangedString() {
+        formatter = new RegexFormatter("(\"\",\"\"");
+        assertEquals("AaBbCc", formatter.format("AaBbCc"));
+    }
+
+    @Test
+    void constructorWithEmptyStringArgumentReturnUnchangedString() {
+        formatter = new RegexFormatter("");
+        assertEquals("AaBbCc", formatter.format("AaBbCc"));
+    }
+
+    @Test
+    void constructorAllowsSpacesBetweenQuotes() {
+        formatter = new RegexFormatter("(\"[A-Z]\", \"\")");
+        assertEquals("abc", formatter.format("AaBbCc"));
+    }
 }