Detect duplicate recipients accross to,cc,bcc

src/main/java/hudson/plugins/emailext/ExtendedEmailPublisher.java

@@ -67,15 +67,19 @@
 import java.net.SocketException;
 import java.net.URL;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.Date;
+import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Properties;
 import java.util.Set;
 import java.util.logging.Level;
 import java.util.logging.Logger;
+import java.util.stream.Collectors;
 import jenkins.model.Jenkins;
 import org.apache.commons.lang3.StringUtils;
 import org.codehaus.groovy.control.CompilerConfiguration;
@@ -582,12 +586,18 @@
                 return false;
             }
 
-            Address[] allRecipients = msg.getAllRecipients();
+            Address[] allRecipients;
+
             int retries = 0;
             if (executePresendScript(context, msg)) {
                 // presend script might have modified recipients:
                 allRecipients = msg.getAllRecipients();
-                if (allRecipients != null) {
+                if (allRecipients == null || allRecipients.length == 0) {
+                    context.getListener().getLogger().println("No recipients found, email couldn't be sent.");
+
+                    return false;
+                }
+                {
                     if (StringUtils.isNotBlank(getDescriptor().getEmergencyReroute())) {
                         // clear out all the existing recipients
                         msg.setRecipients(Message.RecipientType.TO, (Address[]) null);
@@ -708,11 +718,11 @@
 
                     if (context.getRun().getAction(MailMessageIdAction.class) == null) {
                         context.getRun().addAction(new MailMessageIdAction(msg.getMessageID()));
+                    } else {
+                        context.getListener()
+                                .getLogger()
+                                .println("An attempt to send an e-mail" + " to empty list of recipients, ignored.");
                     }
-                } else {
-                    context.getListener()
-                            .getLogger()
-                            .println("An attempt to send an e-mail" + " to empty list of recipients, ignored.");
                 }
             } else {
                 context.getListener().getLogger().println("Email sending was cancelled" + " by user script.");
@@ -984,6 +994,52 @@
         return descriptor.getMailAccount();
     }
 
+    void logDuplicateRecipients(
+            ExtendedEmailPublisherContext context,
+            Set<InternetAddress> to,
+            Set<InternetAddress> cc,
+            Set<InternetAddress> bcc) {
+
+        Set<String> toEmails =
+                to.stream().map(a -> a.getAddress().toLowerCase()).collect(Collectors.toSet());
+
+        Set<String> seen = new HashSet<>();
+        to.removeIf(addr -> !seen.add(addr.getAddress().toLowerCase()));
+
+        seen.clear();
+        cc.removeIf(addr -> {
+            String email = addr.getAddress().toLowerCase();
+            return !seen.add(email) || toEmails.contains(email);
+        });
+
+        Set<String> ccEmails =
+                cc.stream().map(a -> a.getAddress().toLowerCase()).collect(Collectors.toSet());
+
+        List<String> order = Arrays.asList("TO", "CC", "BCC");
+
+        bcc.removeIf(addr -> {
+            String email = addr.getAddress().toLowerCase();
+
+            if (toEmails.contains(email)) {
+                return true;
+            }
+
+            if (ccEmails.contains(email)) {
+
+                List<String> locations = new ArrayList<>(Arrays.asList("CC", "BCC"));
+                locations.sort(Comparator.comparingInt(order::indexOf));
+
+                context.getListener()
+                        .getLogger()
+                        .println("Duplicate recipient detected: " + email + " in " + locations);
+
+                return false;
+            }
+
+            return false;
+        });
+    }
+
     private MimeMessage createMail(ExtendedEmailPublisherContext context, InternetAddress fromAddress, Session session)
             throws MessagingException, UnsupportedEncodingException {
         ExtendedEmailPublisherDescriptor descriptor = getDescriptor();
@@ -1099,6 +1155,8 @@
         excludeNotAllowedDomains(context, cc);
         excludeNotAllowedDomains(context, bcc);
 
+        logDuplicateRecipients(context, to, cc, bcc);
+
         //
         msg.setRecipients(Message.RecipientType.TO, to.toArray(new InternetAddress[0]));
         if (!cc.isEmpty()) {

src/test/java/hudson/plugins/emailext/ExtendedEmailPublisherTest.java

@@ -7,6 +7,7 @@
 import static org.hamcrest.Matchers.hasItems;
 import static org.hamcrest.Matchers.not;
 import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.mock;
 
 import edu.umd.cs.findbugs.annotations.NonNull;
 import hudson.Launcher;
@@ -18,6 +19,7 @@
 import hudson.model.FreeStyleProject;
 import hudson.model.Item;
 import hudson.model.Result;
+import hudson.model.Run;
 import hudson.model.TaskListener;
 import hudson.model.User;
 import hudson.plugins.emailext.plugins.EmailTrigger;
@@ -41,18 +43,23 @@
 import hudson.security.SecurityRealm;
 import hudson.tasks.Builder;
 import hudson.tasks.Mailer;
+import hudson.util.StreamTaskListener;
 import jakarta.mail.Address;
 import jakarta.mail.BodyPart;
 import jakarta.mail.Message;
 import jakarta.mail.MessagingException;
 import jakarta.mail.Session;
+import jakarta.mail.internet.InternetAddress;
 import jakarta.mail.internet.MimeBodyPart;
 import jakarta.mail.internet.MimeMessage;
 import jakarta.mail.internet.MimeMultipart;
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.concurrent.TimeUnit;
 import jenkins.model.Jenkins;
 import jenkins.model.JenkinsLocationConfiguration;
@@ -2166,4 +2173,99 @@ void testStillFailingTriggerShouldBypassThrottling() throws Exception {
                 Mailbox.get("[email protected]").size(),
                 "We should only have one email since the first failure doesn't count as 'still failing'.");
     }
+
+    @Test
+    public void testDuplicateLoggedForCcAndBcc() throws Exception {
+
+        ExtendedEmailPublisher publisher = new ExtendedEmailPublisher();
+
+        ByteArrayOutputStream logStream = new ByteArrayOutputStream();
+        TaskListener listener = new StreamTaskListener(logStream);
+
+        Run<?, ?> run = mock(Run.class);
+
+        ExtendedEmailPublisherContext context = new ExtendedEmailPublisherContext(publisher, run, null, null, listener);
+
+        InternetAddress addr1 = new InternetAddress("[email protected]");
+        InternetAddress addr2 = new InternetAddress("[email protected]");
+
+        Set<InternetAddress> to = new LinkedHashSet<>();
+
+        Set<InternetAddress> cc = new LinkedHashSet<>();
+        cc.add(addr1);
+
+        Set<InternetAddress> bcc = new LinkedHashSet<>();
+        bcc.add(addr2);
+
+        publisher.logDuplicateRecipients(context, to, cc, bcc);
+
+        String logs = logStream.toString();
+
+        assertTrue(logs.contains("Duplicate recipient detected"));
+        assertTrue(logs.contains("[email protected]"));
+        assertTrue(logs.contains("CC"));
+        assertTrue(logs.contains("BCC"));
+    }
+
+    @Test
+    public void testDuplicateRemovedFromCcWhenPresentInTo() throws Exception {
+
+        ExtendedEmailPublisher publisher = new ExtendedEmailPublisher();
+
+        ByteArrayOutputStream logStream = new ByteArrayOutputStream();
+        TaskListener listener = new StreamTaskListener(logStream);
+
+        Run<?, ?> run = mock(Run.class);
+
+        ExtendedEmailPublisherContext context = new ExtendedEmailPublisherContext(publisher, run, null, null, listener);
+
+        InternetAddress addr1 = new InternetAddress("[email protected]");
+        InternetAddress addr2 = new InternetAddress("[email protected]");
+
+        Set<InternetAddress> to = new LinkedHashSet<>();
+        to.add(addr1);
+
+        Set<InternetAddress> cc = new LinkedHashSet<>();
+        cc.add(addr2);
+
+        Set<InternetAddress> bcc = new LinkedHashSet<>();
+
+        publisher.logDuplicateRecipients(context, to, cc, bcc);
+
+        // CC should be removed
+        assertTrue(cc.isEmpty());
+    }
+
+    @Test
+    public void testDuplicateRemovedFromBccWhenPresentInTo() throws Exception {
+
+        ExtendedEmailPublisher publisher = new ExtendedEmailPublisher();
+
+        ByteArrayOutputStream logStream = new ByteArrayOutputStream();
+        TaskListener listener = new StreamTaskListener(logStream);
+
+        Run<?, ?> run = mock(Run.class);
+
+        ExtendedEmailPublisherContext context = new ExtendedEmailPublisherContext(publisher, run, null, null, listener);
+
+        InternetAddress addr1 = new InternetAddress("[email protected]");
+        InternetAddress addr2 = new InternetAddress("[email protected]");
+
+        Set<InternetAddress> to = new LinkedHashSet<>();
+        to.add(addr1);
+
+        Set<InternetAddress> cc = new LinkedHashSet<>();
+
+        Set<InternetAddress> bcc = new LinkedHashSet<>();
+        bcc.add(addr2);
+
+        publisher.logDuplicateRecipients(context, to, cc, bcc);
+
+        // BCC should be removed
+        assertTrue(bcc.isEmpty());
+
+        // No logging expected
+        String logs = logStream.toString();
+        assertTrue(!logs.contains("Duplicate recipient detected"));
+    }
 }