From 6f6a4cd22a275ddfba062090aaf9401e96d313da Mon Sep 17 00:00:00 2001
From: Ben Sherman <bentshermann@gmail.com>
Date: Sat, 2 Aug 2025 10:35:13 -0500
Subject: [PATCH] Check for duplicate process/workflow calls in strict syntax

Signed-off-by: Ben Sherman <bentshermann@gmail.com>
---
 .../script/control/VariableScopeVisitor.java  | 14 +++++++
 .../script/control/ScriptResolveTest.groovy   | 40 +++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/modules/nf-lang/src/main/java/nextflow/script/control/VariableScopeVisitor.java b/modules/nf-lang/src/main/java/nextflow/script/control/VariableScopeVisitor.java
index d46da88e28..b1d5ef5b76 100644
--- a/modules/nf-lang/src/main/java/nextflow/script/control/VariableScopeVisitor.java
+++ b/modules/nf-lang/src/main/java/nextflow/script/control/VariableScopeVisitor.java
@@ -16,7 +16,9 @@
 package nextflow.script.control;
 
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
 import nextflow.script.ast.ASTNodeMarker;
 import nextflow.script.ast.AssignmentExpression;
@@ -168,12 +170,15 @@ public void visitFeatureFlag(FeatureFlagNode node) {
         }
     }
 
+    private Set<String> workflowComponents;
+
     private boolean inWorkflowEmit;
 
     @Override
     public void visitWorkflow(WorkflowNode node) {
         vsc.pushScope(node.isEntry() ? EntryWorkflowDsl.class : WorkflowDsl.class);
         currentDefinition = node;
+        workflowComponents = new HashSet<String>();
         node.setVariableScope(currentScope());
 
         declareWorkflowInputs(node.takes);
@@ -185,6 +190,7 @@ public void visitWorkflow(WorkflowNode node) {
         visitWorkflowOutputs(node.emits, "emit");
         visitWorkflowOutputs(node.publishers, "output");
 
+        workflowComponents = null;
         currentDefinition = null;
         vsc.popScope();
     }
@@ -590,6 +596,14 @@ private void checkDataflowMethod(MethodCallExpression node, MethodNode mn) {
             vsc.addError(type + " cannot be called from within a closure", node);
             return;
         }
+        if( mn instanceof ProcessNode || mn instanceof WorkflowNode ) {
+            var name = node.getMethodAsString();
+            if( workflowComponents.contains(name) ) {
+                var type = mn instanceof ProcessNode ? "Process" : "Workflow";
+                vsc.addError(type + " `" + name + "` cannot be called more than once in the same workflow -- use an alias instead", node);
+            }
+            workflowComponents.add(name);
+        }
     }
 
     private static String dataflowMethodType(MethodNode mn) {
diff --git a/modules/nf-lang/src/test/groovy/nextflow/script/control/ScriptResolveTest.groovy b/modules/nf-lang/src/test/groovy/nextflow/script/control/ScriptResolveTest.groovy
index 6c8f9e8e2d..fe10d255dd 100644
--- a/modules/nf-lang/src/test/groovy/nextflow/script/control/ScriptResolveTest.groovy
+++ b/modules/nf-lang/src/test/groovy/nextflow/script/control/ScriptResolveTest.groovy
@@ -256,6 +256,28 @@ class ScriptResolveTest extends Specification {
         errors[0].getStartLine() == 10
         errors[0].getStartColumn() == 9
         errors[0].getOriginalMessage() == 'Processes cannot be called from within a closure'
+
+        when:
+        errors = check(
+            '''\
+            process hello {
+                script:
+                """
+                echo hello
+                """
+            }
+
+            workflow {
+                hello()
+                hello()
+            }
+            '''
+        )
+        then:
+        errors.size() == 1
+        errors[0].getStartLine() == 10
+        errors[0].getStartColumn() == 5
+        errors[0].getOriginalMessage() == 'Process `hello` cannot be called more than once in the same workflow -- use an alias instead'
     }
 
     def 'should report an error for an invalid workflow invocation' () {
@@ -294,6 +316,24 @@ class ScriptResolveTest extends Specification {
         errors[0].getStartLine() == 6
         errors[0].getStartColumn() == 9
         errors[0].getOriginalMessage() == 'Workflows cannot be called from within a closure'
+
+        when:
+        errors = check(
+            '''\
+            workflow hello {
+            }
+
+            workflow {
+                hello()
+                hello()
+            }
+            '''
+        )
+        then:
+        errors.size() == 1
+        errors[0].getStartLine() == 6
+        errors[0].getStartColumn() == 5
+        errors[0].getOriginalMessage() == 'Workflow `hello` cannot be called more than once in the same workflow -- use an alias instead'
     }
 
 }