Add onWorkflowPublish event to TraceObserverV2

modules/nextflow/src/main/groovy/nextflow/Session.groovy

@@ -79,6 +79,7 @@ import nextflow.trace.WorkflowStatsObserver
 import nextflow.trace.event.FilePublishEvent
 import nextflow.trace.event.TaskEvent
 import nextflow.trace.event.WorkflowOutputEvent
+import nextflow.trace.event.WorkflowPublishEvent
 import nextflow.util.Barrier
 import nextflow.util.ConfigHelper
 import nextflow.util.Duration
@@ -1071,6 +1072,10 @@ class Session implements ISession {
         notifyEvent(observersV2, ob -> ob.onWorkflowOutput(event))
     }
 
+    void notifyWorkflowPublish(WorkflowPublishEvent event) {
+        notifyEvent(observersV2, ob -> ob.onWorkflowPublish(event))
+    }
+
     void notifyFilePublish(FilePublishEvent event) {
         notifyEvent(observersV1, ob -> ob.onFilePublish(event.target, event.source))
         notifyEvent(observersV2, ob -> ob.onFilePublish(event))

modules/nextflow/src/main/groovy/nextflow/extension/PublishOp.groovy

@@ -26,6 +26,7 @@ import nextflow.exception.ScriptRuntimeException
 import nextflow.processor.PublishDir
 import nextflow.trace.event.FilePublishEvent
 import nextflow.trace.event.WorkflowOutputEvent
+import nextflow.trace.event.WorkflowPublishEvent
 import nextflow.util.CsvWriter
 /**
  * Publish a workflow output.
@@ -114,6 +115,9 @@ class PublishOp {
         final normalized = normalizePaths(value, targetResolver)
         log.trace "Normalized record for index file: ${normalized}"
         indexRecords << normalized
+
+        // notify observers
+        session.notifyWorkflowPublish(new WorkflowPublishEvent(name, normalized))
     }
 
     /**

modules/nextflow/src/main/groovy/nextflow/trace/TraceObserverV2.groovy

@@ -23,6 +23,7 @@ import nextflow.processor.TaskProcessor
 import nextflow.trace.event.FilePublishEvent
 import nextflow.trace.event.TaskEvent
 import nextflow.trace.event.WorkflowOutputEvent
+import nextflow.trace.event.WorkflowPublishEvent
 
 /**
  * Interface for consuming workflow lifecycle events.
@@ -127,6 +128,15 @@ interface TraceObserverV2 {
      */
     default void onWorkflowOutput(WorkflowOutputEvent event) {}
 
+    /**
+     * Invoked when a value is being published to a workflow output.
+     * Unlike {@link #onWorkflowOutput} which fires after all values are
+     * published, this fires for each value as it is published.
+     *
+     * @param event
+     */
+    default void onWorkflowPublish(WorkflowPublishEvent event) {}
+
     /**
      * Invoked when a file is published, either by a `publishDir` directive
      * or a workflow output.

modules/nextflow/src/main/groovy/nextflow/trace/event/WorkflowPublishEvent.groovy

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2013-2024, Seqera Labs
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package nextflow.trace.event
+
+import groovy.transform.Canonical
+import groovy.transform.CompileStatic
+
+/**
+ * Models a workflow publish event, fired for each value
+ * as it is published to a workflow output.
+ *
+ * @author Rob Syme <rob.syme@gmail.com>
+ */
+@Canonical
+@CompileStatic
+class WorkflowPublishEvent {
+    /**
+     * The name of the workflow output.
+     */
+    String name
+    /**
+     * The value being published.
+     */
+    Object value
+}

modules/nextflow/src/test/groovy/nextflow/script/OutputDslTest.groovy

@@ -10,6 +10,7 @@ import nextflow.Session
 import nextflow.SysEnv
 import nextflow.trace.event.FilePublishEvent
 import nextflow.trace.event.WorkflowOutputEvent
+import nextflow.trace.event.WorkflowPublishEvent
 import spock.lang.Specification
 /**
  *
@@ -86,6 +87,8 @@ class OutputDslTest extends Specification {
             "${outputDir}/barbar/file2.txt"
             """.stripIndent()
         and:
+        1 * session.notifyWorkflowPublish(new WorkflowPublishEvent('foo', file1))
+        1 * session.notifyWorkflowPublish(new WorkflowPublishEvent('bar', file2))
         1 * session.notifyFilePublish(new FilePublishEvent(file1, outputDir.resolve('foo/file1.txt'), null))
         1 * session.notifyFilePublish(new FilePublishEvent(file2, outputDir.resolve('barbar/file2.txt'), ['foo', 'bar']))
         1 * session.notifyWorkflowOutput(new WorkflowOutputEvent('foo', [outputDir.resolve('foo/file1.txt')], null))
@@ -127,6 +130,7 @@ class OutputDslTest extends Specification {
         then:
         outputDir.resolve('file1.txt').text == 'Hello'
         and:
+        1 * session.notifyWorkflowPublish(new WorkflowPublishEvent('foo', file1))
         1 * session.notifyFilePublish(new FilePublishEvent(file1, outputDir.resolve('file1.txt'), null))
         1 * session.notifyWorkflowOutput(new WorkflowOutputEvent('foo', [outputDir.resolve('file1.txt')], null))
 
@@ -165,6 +169,7 @@ class OutputDslTest extends Specification {
         dsl.apply(session)
         await(dsl)
         then:
+        1 * session.notifyWorkflowPublish(new WorkflowPublishEvent('foo', record))
         0 * session.notifyFilePublish(_)
         1 * session.notifyWorkflowOutput(new WorkflowOutputEvent('foo', [ record ], null))