[1986] Make ServiceMethod fail if parameters don't match arity

CHANGELOG.adoc

@@ -54,6 +54,8 @@ Publishing a project that contains representations now produces libraries that a
 - https://github.com/eclipse-syson/syson/issues/1970[#1970] [export] Implement textual export of `AllocationUsage` and `AllocationDefinition`.
 - https://github.com/eclipse-syson/syson/issues/1948[#1948] [diagrams] Add _New Satisfy_ tool on `RequirementUsage` graphical nodes. This tool allows to create a `SatisfyRequirementUsage` on the selected `RequirementUsage`.
 Also add a  _New Satisfy Requirement_ graphical edge tool between `Feature` graphical nodes and `RequirementUsage` graphical nodes.
+- https://github.com/eclipse-syson/syson/issues/1986[#1986] [services] Make `ServiceMethod#aql` and `ServiceMethod#aqlSelf` throw an exception if the provided parameters don't match the service method arity.
+As a result, the application won't start if a service call is constructed with an invalid number of arguments.
 
 === New features
 

backend/services/syson-services/src/main/java/org/eclipse/syson/util/ServiceMethod.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2025 Obeo.
+ * Copyright (c) 2025, 2026 Obeo.
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
  * which accompanies this distribution, and is available at
@@ -16,6 +16,7 @@
 import java.lang.invoke.SerializedLambda;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.text.MessageFormat;
 import java.util.Arrays;
 
 /**
@@ -81,8 +82,11 @@ public final class ServiceMethod {
 
     private final String name;
 
-    private ServiceMethod(String name) {
+    private final int arity;
+
+    private ServiceMethod(String name, int arity) {
         this.name = name;
+        this.arity = arity;
     }
 
     /**
@@ -105,6 +109,7 @@ public String name() {
      * @return A full AQL expression string
      */
     public String aqlSelf(String... params) {
+        this.checkArity(params);
         if (params == null || params.length == 0) {
             return AQLUtils.getSelfServiceCallExpression(this.name);
         }
@@ -128,6 +133,7 @@ public String aql(String var, String... params) {
         if (var == null || var.isEmpty()) {
             throw new IllegalArgumentException("var must be a non empty AQL variable name");
         } else {
+            this.checkArity(params);
             if (params == null || params.length == 0) {
                 aqlString = AQLUtils.getServiceCallExpression(var, this.name);
             }
@@ -143,49 +149,49 @@ public String aql(String var, String... params) {
      * Instance method with signature {@code R method(T self)}.
      */
     public static <S, T> ServiceMethod of0(Inst0<S, T> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 0);
     }
 
     /**
      * Instance method with signature {@code R method(T self, P1 p1)}.
      */
     public static <S, T, P1> ServiceMethod of1(Inst1<S, T, P1> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 1);
     }
 
     /**
      * Instance method with signature {@code R method(T self, P1 p1, P2 p2)}.
      */
     public static <S, T, P1, P2> ServiceMethod of2(Inst2<S, T, P1, P2> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 2);
     }
 
     /**
      * Instance method with signature {@code R method(T self, P1 p1, P2 p2, P3 p3)}.
      */
     public static <S, T, P1, P2, P3> ServiceMethod of3(Inst3<S, T, P1, P2, P3> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 3);
     }
 
     /**
      * Instance method with signature {@code R method(T self, P1 p1, P2 p2, P3 p3, P4 p4)}.
      */
     public static <S, T, P1, P2, P3, P4> ServiceMethod of4(Inst4<S, T, P1, P2, P3, P4> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 4);
     }
 
     /**
      * Instance method with signature {@code R method(T self, P1 p1, P2 p2, P3 p3, P4 p4, P5 p5)}.
      */
     public static <S, T, P1, P2, P3, P4, P5> ServiceMethod of5(Inst5<S, T, P1, P2, P3, P4, P5> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 5);
     }
 
     /**
      * Instance method with signature {@code R method(T self, P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6)}.
      */
     public static <S, T, P1, P2, P3, P4, P5, P6> ServiceMethod of6(Inst6<S, T, P1, P2, P3, P4, P5, P6> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 6);
     }
 
     // ---------------------- Factories for static methods ----------------------
@@ -194,28 +200,28 @@ public static <S, T, P1, P2, P3, P4, P5, P6> ServiceMethod of6(Inst6<S, T, P1, P
      * Static method with signature {@code R method(T self)}.
      */
     public static <T> ServiceMethod ofStatic0(IStat0<T> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 0);
     }
 
     /**
      * Static method with signature {@code R method(T self, P1 p1)}.
      */
     public static <T, P1> ServiceMethod ofStatic1(IStat1<T, P1> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 1);
     }
 
     /**
      * Static method with signature {@code R method(T self, P1 p1, P2 p2)}.
      */
     public static <T, P1, P2> ServiceMethod ofStatic2(IStat2<T, P1, P2> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 2);
     }
 
     /**
      * Static method with signature {@code R method(T self, P1 p1, P2 p2, P3 p3)}.
      */
     public static <T, P1, P2, P3> ServiceMethod ofStatic3(IStat3<T, P1, P2, P3> ref) {
-        return new ServiceMethod(methodName(ref));
+        return new ServiceMethod(methodName(ref), 3);
     }
 
     // ---------------------- SAMs for method references ----------------------
@@ -431,5 +437,24 @@ private static String methodName(Serializable lambdaRef) {
             throw new IllegalStateException("Cannot resolve method name from lambda", e);
         }
     }
+
+    /**
+     * Checks that the provided {@code params} array matches the arity of the service method.
+     *
+     * @param params the parameters passed to the service method (excluding self)
+     *
+     * @throws IllegalArgumentException if the provided {@code params} doesn't match the arity of the service method.
+     */
+    private void checkArity(String... params) {
+        int paramLength;
+        if (params == null) {
+            paramLength = 0;
+        } else {
+            paramLength = params.length;
+        }
+        if (this.arity != paramLength) {
+            throw new IllegalArgumentException(MessageFormat.format("Service {0} has an arity of {1} but {2} parameters were provided", this.name, this.arity, paramLength));
+        }
+    }
 }
 

backend/services/syson-services/src/test/java/org/eclipse/syson/util/ServiceMethodTest.java

@@ -0,0 +1,47 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Obeo.
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.syson.util;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+/**
+ * ServiceMethod-related tests.
+ *
+ * @author gdaniel
+ */
+public class ServiceMethodTest {
+
+    @Test
+    @DisplayName("GIVEN a service method with arity 0, WHEN an AQL expression is constructed with 0 parameter, THEN the expression is returned")
+    public void givenServiceMethodWithArity0WhenAQLExpressionIsConstructedWith0ParameterThenExpressionIsReturned() {
+        String expression = ServiceMethod.of0(ServiceMethodTest::serviceWithArity0).aqlSelf();
+        assertThat(expression).isEqualTo("aql:self.serviceWithArity0()");
+        expression = ServiceMethod.of0(ServiceMethodTest::serviceWithArity0).aql("var");
+        assertThat(expression).isEqualTo("aql:var.serviceWithArity0()");
+    }
+
+    @Test
+    @DisplayName("GIVEN a service method with arity 0, WHEN an AQL expression is constructed with 1 parameter, THEN an exception is thrown")
+    public void givenServiceMethodWithArity0WhenAQLExpressionIsConstructedWith1ParameterThenExceptionIsThrown() {
+        assertThatThrownBy(() -> ServiceMethod.of0(ServiceMethodTest::serviceWithArity0).aqlSelf("param1")).isInstanceOf(IllegalArgumentException.class);
+        assertThatThrownBy(() -> ServiceMethod.of0(ServiceMethodTest::serviceWithArity0).aql("var", "param1")).isInstanceOf(IllegalArgumentException.class);
+    }
+
+    private Object serviceWithArity0(Object self) {
+        return null;
+    }
+}