RelNodeVisitCoverageTest for test RelShuttle visit coverage

core/build.gradle.kts

@@ -93,6 +93,7 @@ dependencies {
     testImplementation("net.hydromatic:foodmart-queries")
     testImplementation("net.hydromatic:quidem")
     testImplementation("org.apache.calcite.avatica:avatica-server")
+    testImplementation("io.github.classgraph:classgraph:4.8.173")
     testImplementation("org.apache.commons:commons-pool2")
     testImplementation("org.hsqldb:hsqldb::jdk8")
     testImplementation("sqlline:sqlline")

core/src/test/java/org/apache/calcite/test/RelNodeVisitCoverageTest.java

@@ -0,0 +1,75 @@
+package org.apache.calcite.test;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import io.github.classgraph.ClassGraph;
+import io.github.classgraph.ClassInfo;
+import io.github.classgraph.ScanResult;
+
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.RelShuttle;
+
+import org.junit.jupiter.api.Test;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+
+/**
+ * Discovers every concrete {@link RelNode} implementation on the classpath and
+ * verifies {@link RelShuttle} declares a compatible {@code visit} method.
+ */
+class RelNodeVisitCoverageTest {
+
+  @Test void relShuttleCoversAllRelNodes() {
+    Set<Class<? extends RelNode>> relNodeClasses = findRelNodeClasses();
+    Set<Class<?>> visitParameters = visitParameterTypes();
+
+    Set<Class<? extends RelNode>> missing = relNodeClasses.stream()
+        .filter(relClass -> visitParameters.stream()
+            .noneMatch(relClass::isAssignableFrom))
+        .collect(Collectors.toCollection(() ->
+            new TreeSet<>(Comparator.comparing(Class::getName))));
+
+    assertTrue(missing.isEmpty(),
+        () -> "RelShuttle.visit(...) is missing for: " + missing);
+  }
+
+  private Set<Class<?>> visitParameterTypes() {
+    Set<Class<?>> visitParameters = new HashSet<>();
+    for (Method method : RelShuttle.class.getMethods()) {
+      if ("visit".equals(method.getName()) && method.getParameterCount() == 1) {
+        visitParameters.add(method.getParameterTypes()[0]);
+      }
+    }
+    return visitParameters;
+  }
+
+  private Set<Class<? extends RelNode>> findRelNodeClasses() {
+    Set<Class<? extends RelNode>> result =
+        new TreeSet<>(Comparator.comparing(Class::getName));
+    try (ScanResult scan = new ClassGraph()
+        .enableClassInfo()
+        .ignoreClassVisibility()
+        .acceptPackages(RelNode.class.getPackageName())
+        .scan()) {
+      for (ClassInfo classInfo : scan.getClassesImplementing(RelNode.class.getName())) {
+        Class<? extends RelNode> clazz = classInfo.loadClass(RelNode.class);
+        if (isConcreteRelNode(clazz)) {
+          result.add(clazz);
+        }
+      }
+    }
+    return result;
+  }
+
+  private boolean isConcreteRelNode(Class<?> clazz) {
+    return RelNode.class.isAssignableFrom(clazz)
+        && !clazz.isInterface()
+        && !Modifier.isAbstract(clazz.getModifiers());
+  }
+}