[Core] Log warning when classes could not be loaded

Fixes: #2229

Author: mpkorstanje

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
  * [Core] Pass class loader to ServiceLoader.load invocations ([#2220](https://github.com/cucumber/cucumber-jvm/issues/2220) M.P. Korstanje)
+ * [Core] Log warnings when classes could not be loaded ([#2235](https://github.com/cucumber/cucumber-jvm/issues/2235) M.P. Korstanje)
 
 ## [6.9.1] (2020-12-14)
 

core/src/main/java/io/cucumber/core/exception/UnrecoverableExceptions.java

@@ -0,0 +1,14 @@
+package io.cucumber.core.exception;
+
+public final class UnrecoverableExceptions {
+
+    private UnrecoverableExceptions() {
+    }
+
+    public static void rethrowIfUnrecoverable(Throwable throwable) {
+        if (throwable instanceof OutOfMemoryError) {
+            ExceptionUtils.throwAsUncheckedException(throwable);
+        }
+    }
+
+}

core/src/main/java/io/cucumber/core/resource/ClasspathScanner.java

@@ -1,5 +1,6 @@
 package io.cucumber.core.resource;
 
+import io.cucumber.core.exception.UnrecoverableExceptions;
 import io.cucumber.core.logging.Logger;
 import io.cucumber.core.logging.LoggerFactory;
 
@@ -95,16 +96,30 @@ private Function<Path, Consumer<Path>> processClassFiles(
     ) {
         return baseDir -> classFile -> {
             String fqn = determineFullyQualifiedClassName(baseDir, basePackageName, classFile);
-            try {
-                Optional.of(getClassLoader().loadClass(fqn))
-                        .filter(classFilter)
-                        .ifPresent(classConsumer);
-            } catch (ClassNotFoundException | NoClassDefFoundError e) {
-                log.debug(e, () -> "Failed to load class " + fqn);
-            }
+            safelyLoadClass(fqn)
+                    .filter(classFilter)
+                    .ifPresent(classConsumer);
         };
     }
 
+    private Optional<Class<?>> safelyLoadClass(String fqn) {
+        try {
+            return Optional.ofNullable(getClassLoader().loadClass(fqn));
+        } catch (Throwable e) {
+            UnrecoverableExceptions.rethrowIfUnrecoverable(e);
+            log.warn(e, () -> "" +
+                    "Failed to class '" + fqn + "'.\n" +
+                    "By default Cucumber scans the classpath for step definitions.\n" +
+                    "You can restrict this by configuring the glue path.\n" +
+                    "\n" +
+                    "Examples:\n" +
+                    " - @CucumberOptions(glue = \"com.example.application\")\n" +
+                    " - src/test/resources/junit-platform.properties   cucumber.glue=com.example.application\n" +
+                    " - src/test/resources/cucumber.properties         cucumber.glue=com.example.application\n");
+        }
+        return Optional.empty();
+    }
+
     public List<Class<?>> scanForClassesInPackage(String packageName) {
         return scanForClassesInPackage(packageName, NULL_FILTER);
     }

java/src/main/java/io/cucumber/java/MethodScanner.java

@@ -1,5 +1,9 @@
 package io.cucumber.java;
 
+import io.cucumber.core.exception.UnrecoverableExceptions;
+import io.cucumber.core.logging.Logger;
+import io.cucumber.core.logging.LoggerFactory;
+
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
@@ -9,6 +13,8 @@
 
 final class MethodScanner {
 
+    private static final Logger log = LoggerFactory.getLogger(MethodScanner.class);
+
     private MethodScanner() {
     }
 
@@ -21,11 +27,29 @@ static void scan(Class<?> aClass, BiConsumer<Method, Annotation> consumer) {
         if (!isInstantiable(aClass)) {
             return;
         }
-        for (Method method : aClass.getMethods()) {
+        for (Method method : safelyGetMethods(aClass)) {
             scan(consumer, aClass, method);
         }
     }
 
+    private static Method[] safelyGetMethods(Class<?> aClass) {
+        try {
+            return aClass.getMethods();
+        } catch (Throwable e) {
+            UnrecoverableExceptions.rethrowIfUnrecoverable(e);
+            log.warn(e, () -> "" +
+                    "Failed to load methods of class '" + aClass.getName() + "'.\n" +
+                    "By default Cucumber scans the classpath for step definitions.\n" +
+                    "You can restrict this by configuring the glue path.\n" +
+                    "\n" +
+                    "Examples:\n" +
+                    " - @CucumberOptions(glue = \"com.example.application\")\n" +
+                    " - src/test/resources/junit-platform.properties   cucumber.glue=com.example.application\n" +
+                    " - src/test/resources/cucumber.properties         cucumber.glue=com.example.application\n");
+        }
+        return new Method[0];
+    }
+
     private static boolean isInstantiable(Class<?> clazz) {
         boolean isNonStaticInnerClass = !Modifier.isStatic(clazz.getModifiers()) && clazz.getEnclosingClass() != null;
         return Modifier.isPublic(clazz.getModifiers()) && !Modifier.isAbstract(clazz.getModifiers())

java/src/test/java/io/cucumber/java/MethodScannerTest.java

@@ -2,6 +2,7 @@
 
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
 
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;