Provide more context when the code of a value cannot be generated

Closes gh-29118

spring-beans/src/main/java/org/springframework/beans/factory/aot/BeanDefinitionPropertyValueCodeGenerator.java

@@ -85,7 +85,30 @@ class BeanDefinitionPropertyValueCodeGenerator {
 	CodeBlock generateCode(@Nullable Object value) {
 		ResolvableType type = (value != null) ? ResolvableType.forInstance(value)
 				: ResolvableType.NONE;
-		return generateCode(value, type);
+		try {
+			return generateCode(value, type);
+		}
+		catch (Exception ex) {
+			throw new IllegalArgumentException(buildErrorMessage(value, type), ex);
+		}
+	}
+
+	private CodeBlock generateCodeForElement(@Nullable Object value, ResolvableType type) {
+		try {
+			return generateCode(value, type);
+		}
+		catch (Exception ex) {
+			throw new IllegalArgumentException(buildErrorMessage(value, type), ex);
+		}
+	}
+
+	private static String buildErrorMessage(@Nullable Object value, ResolvableType type) {
+		StringBuilder message = new StringBuilder("Failed to generate code for '");
+		message.append(value).append("'");
+		if (type != ResolvableType.NONE) {
+			message.append(" with type ").append(type);
+		}
+		return message.toString();
 	}
 
 	private CodeBlock generateCode(@Nullable Object value, ResolvableType type) {
@@ -98,8 +121,7 @@ class BeanDefinitionPropertyValueCodeGenerator {
 				return code;
 			}
 		}
-		throw new IllegalArgumentException(
+		throw new IllegalArgumentException("Code generation does not support " + type);
-				"'type' " + type + " must be supported for instance code generation");
 	}
 
 
@@ -304,7 +326,7 @@ class BeanDefinitionPropertyValueCodeGenerator {
 			while (iterator.hasNext()) {
 				Object element = iterator.next();
 				code.add("$L", BeanDefinitionPropertyValueCodeGenerator.this
-						.generateCode(element, elementType));
+						.generateCodeForElement(element, elementType));
 				if (iterator.hasNext()) {
 					code.add(", ");
 				}
@@ -371,9 +393,9 @@ class BeanDefinitionPropertyValueCodeGenerator {
 				Entry<?, ?> entry = iterator.next();
 				code.add("$T.entry($L,$L)", Map.class,
 						BeanDefinitionPropertyValueCodeGenerator.this
-								.generateCode(entry.getKey(), keyType),
+								.generateCodeForElement(entry.getKey(), keyType),
 						BeanDefinitionPropertyValueCodeGenerator.this
-								.generateCode(entry.getValue(), valueType));
+								.generateCodeForElement(entry.getValue(), valueType));
 				if (iterator.hasNext()) {
 					code.add(", ");
 				}
@@ -457,9 +479,9 @@ class BeanDefinitionPropertyValueCodeGenerator {
 			while (iterator.hasNext()) {
 				Entry<K, V> entry = iterator.next();
 				CodeBlock keyCode = BeanDefinitionPropertyValueCodeGenerator.this
-						.generateCode(entry.getKey(), keyType);
+						.generateCodeForElement(entry.getKey(), keyType);
 				CodeBlock valueCode = BeanDefinitionPropertyValueCodeGenerator.this
-						.generateCode(entry.getValue(), valueType);
+						.generateCodeForElement(entry.getValue(), valueType);
 				if (!useOfEntries) {
 					code.add("$L, $L", keyCode, valueCode);
 				}
@@ -490,9 +512,9 @@ class BeanDefinitionPropertyValueCodeGenerator {
 						LinkedHashMap.class, map.size());
 				map.forEach((key, value) -> method.addStatement("map.put($L, $L)",
 						BeanDefinitionPropertyValueCodeGenerator.this
-								.generateCode(key, keyType),
+								.generateCodeForElement(key, keyType),
 						BeanDefinitionPropertyValueCodeGenerator.this
-								.generateCode(value, valueType)));
+								.generateCodeForElement(value, valueType)));
 				method.addStatement("return map");
 			});
 			return CodeBlock.of("$L()", generatedMethod.getName());

spring-beans/src/test/java/org/springframework/beans/factory/aot/BeanDefinitionPropertyValueCodeGeneratorTests.java

@@ -50,6 +50,7 @@ import org.springframework.javapoet.MethodSpec;
 import org.springframework.javapoet.ParameterizedTypeName;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 
 /**
  * Tests for {@link BeanDefinitionPropertyValueCodeGenerator}.
@@ -492,4 +493,48 @@ class BeanDefinitionPropertyValueCodeGeneratorTests {
 
 	}
 
+	@Nested
+	static class ExceptionTests {
+
+		@Test
+		void generateWhenUnsupportedDataTypeThrowsException() {
+			SampleValue sampleValue = new SampleValue("one");
+			assertThatIllegalArgumentException().isThrownBy(() -> generateCode(sampleValue))
+					.withMessageContaining("Failed to generate code for")
+					.withMessageContaining(sampleValue.toString())
+					.withMessageContaining(SampleValue.class.getName())
+					.havingCause()
+					.withMessageContaining("Code generation does not support")
+					.withMessageContaining(SampleValue.class.getName());
+		}
+
+		@Test
+		void generateWhenListOfUnsupportedElement() {
+			SampleValue one = new SampleValue("one");
+			SampleValue two = new SampleValue("two");
+			List<SampleValue> list = List.of(one, two);
+			assertThatIllegalArgumentException().isThrownBy(() -> generateCode(list))
+					.withMessageContaining("Failed to generate code for")
+					.withMessageContaining(list.toString())
+					.withMessageContaining(list.getClass().getName())
+					.havingCause()
+					.withMessageContaining("Failed to generate code for")
+					.withMessageContaining(one.toString())
+					.withMessageContaining("?")
+					.havingCause()
+					.withMessageContaining("Code generation does not support ?");
+		}
+
+		private void generateCode(Object value) {
+			TestGenerationContext context = new TestGenerationContext();
+			GeneratedClass generatedClass = context.getGeneratedClasses()
+					.addForFeature("Test", type -> {});
+			new BeanDefinitionPropertyValueCodeGenerator(generatedClass.getMethods())
+					.generateCode(value);
+		}
+
+		record SampleValue(String name) {}
+
+	}
+
 }