Update CheckstyleValidator.java

qulice-checkstyle/src/main/java/com/qulice/checkstyle/CheckstyleValidator.java

@@ -4,6 +4,7 @@
  */
 package com.qulice.checkstyle;
 
+import com.jcabi.log.Logger;
 import com.puppycrawl.tools.checkstyle.Checker;
 import com.puppycrawl.tools.checkstyle.ConfigurationLoader;
 import com.puppycrawl.tools.checkstyle.PropertiesExpander;
@@ -66,23 +67,37 @@ public CheckstyleValidator(final Environment env) {
     @Override
     @SuppressWarnings("PMD.AvoidInstantiatingObjectsInLoops")
     public Collection<Violation> validate(final Collection<File> files) {
+        if (files == null) {
+            throw new IllegalArgumentException("Files collection cannot be null");
+        }
         final List<File> sources = this.getNonExcludedFiles(files);
         try {
             this.checker.process(sources);
         } catch (final CheckstyleException ex) {
-            throw new IllegalStateException("Failed to process files", ex);
+            throw new IllegalStateException(
+                String.format("Failed to process files: %s", ex.getMessage()),
+                ex
+            );
         }
         final List<AuditEvent> events = this.listener.events();
         final Collection<Violation> results = new LinkedList<>();
         for (final AuditEvent event : events) {
             final String check = event.getSourceName();
+            final String checkname = check.substring(check.lastIndexOf('.') + 1);
+            final String filename = event.getFileName();
+            final String line = String.valueOf(event.getLine());
+            final String message = event.getMessage();
+            if (filename == null) {
+                Logger.warn(this, "Skipping violation with null filename for check %s", checkname);
+                continue;
+            }
             results.add(
                 new Violation.Default(
                     this.name(),
-                    check.substring(check.lastIndexOf('.') + 1),
-                    event.getFileName(),
-                    String.valueOf(event.getLine()),
-                    event.getMessage()
+                    checkname,
+                    filename,
+                    line,
+                    message
                 )
             );
         }