added validation for header in setHeader in RegexpHeaderCheck.java to provide better feedback when an invalid Pattern is specified (was InvocationTargetException only before). Changes are made base on @krichter722 commit. Issue #897

src/main/java/com/puppycrawl/tools/checkstyle/checks/header/RegexpHeaderCheck.java

@@ -26,9 +26,11 @@ import java.util.List;
 import java.util.regex.Pattern;
 import java.util.regex.PatternSyntaxException;
 
+import com.puppycrawl.tools.checkstyle.Utils;
 import org.apache.commons.beanutils.ConversionException;
 
 import com.google.common.collect.Lists;
+import org.apache.commons.lang3.StringUtils;
 
 /**
  * Checks the header of the source against a header file that contains a
@@ -145,4 +147,22 @@ public class RegexpHeaderCheck extends AbstractHeaderCheck
         }
     }
 
+    /**
+     * Validates the {@code header} by compiling it with
+     * {@link Pattern#compile(java.lang.String) } and throws
+     * {@link PatternSyntaxException} if {@code header} isn't a valid pattern.
+     * @param header the header value to validate and set (in that order)
+     */
+    @Override
+    public void setHeader(String header)
+    {
+        if (StringUtils.isBlank(header)) {
+            return;
+        }
+        if (!Utils.isPatternValid(header)) {
+            throw new ConversionException("Unable to parse format: " + header);
+        }
+        super.setHeader(header);
+    }
+
 }

src/test/java/com/puppycrawl/tools/checkstyle/checks/header/RegexpHeaderCheckTest.java

@@ -0,0 +1,94 @@
+////////////////////////////////////////////////////////////////////////////////
+// checkstyle: Checks Java source code for adherence to a set of rules.
+// Copyright (C) 2001-2015 the original author or authors.
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+////////////////////////////////////////////////////////////////////////////////
+package com.puppycrawl.tools.checkstyle.checks.header;
+
+import org.apache.commons.beanutils.ConversionException;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ *
+ * @author richter
+ */
+public class RegexpHeaderCheckTest
+{
+
+    public RegexpHeaderCheckTest()
+    {
+    }
+
+    /**
+     * Test of setHeader method, of class RegexpHeaderCheck.
+     */
+    @Test
+    public void testSetHeaderNull()
+    {
+        // check null passes
+        RegexpHeaderCheck instance = new RegexpHeaderCheck();
+        // recreate for each test because multiple invocations fail
+        String header = null;
+        instance.setHeader(header);
+    }
+
+    /**
+     * Test of setHeader method, of class RegexpHeaderCheck.
+     */
+    @Test
+    public void testSetHeaderEmpty()
+    {
+        // check null passes
+        RegexpHeaderCheck instance = new RegexpHeaderCheck();
+        // check empty string passes
+        instance = new RegexpHeaderCheck();
+        String header = "";
+        instance.setHeader(header);
+    }
+
+    /**
+     * Test of setHeader method, of class RegexpHeaderCheck.
+     */
+    @Test
+    public void testSetHeaderSimple()
+    {
+        RegexpHeaderCheck instance = new RegexpHeaderCheck();
+        // check valid header passes
+        instance = new RegexpHeaderCheck();
+        String header = "abc.*";
+        instance.setHeader(header);
+    }
+
+    /**
+     * Test of setHeader method, of class RegexpHeaderCheck.
+     */
+    @Test
+    public void testSetHeader()
+    {
+        // check invalid header passes
+        RegexpHeaderCheck instance = new RegexpHeaderCheck();
+        String header = "^/**\\n * Licensed to the Apache Software Foundation (ASF)";
+        try {
+            instance.setHeader(header);
+            Assert.fail(String.format("%s should have been thrown", ConversionException.class));
+        }
+        catch (ConversionException ex) {
+            // expected
+        }
+    }
+
+}