Validate aggregation query method on query method creation.

This commit makes sure to fail early if an annotated string based annotation does not contain a syntactically valid pipeline.

Original pull request: #4547
Closes #4546

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/MongoQueryMethod.java

@@ -38,6 +38,7 @@ import org.springframework.data.mongodb.repository.Meta;
 import org.springframework.data.mongodb.repository.Query;
 import org.springframework.data.mongodb.repository.Tailable;
 import org.springframework.data.mongodb.repository.Update;
+import org.springframework.data.mongodb.util.BsonUtils;
 import org.springframework.data.projection.ProjectionFactory;
 import org.springframework.data.repository.core.RepositoryMetadata;
 import org.springframework.data.repository.query.QueryMethod;
@@ -456,6 +457,16 @@ public class MongoQueryMethod extends QueryMethod {
 				}
 			}
 		}
+		if (hasAnnotatedAggregation()) {
+			for (String stage : getAnnotatedAggregation()) {
+				if (BsonUtils.isJsonArray(stage)) {
+					throw new IllegalStateException("""
+							Invalid aggregation pipeline. Please split Aggregation.pipeline from "[{...}, {...}]" to "{...}", "{...}".
+							Offending Method: %s.%s
+							""".formatted(method.getDeclaringClass().getSimpleName(), method.getName()));
+				}
+			}
+		}
 	}
 
 	private boolean isNumericOrVoidReturnValue() {

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/query/MongoQueryMethodUnitTests.java

@@ -311,6 +311,15 @@ public class MongoQueryMethodUnitTests {
 		assertThat(method.getAnnotatedCollation()).isEqualTo("de_AT");
 	}
 
+	@Test // GH-4546
+	void errorsOnInvalidAggregation() throws Exception {
+
+		assertThatExceptionOfType(IllegalStateException.class) //
+				.isThrownBy(() -> queryMethod(InvalidAggregationMethodRepo.class, "findByAggregation").verify()) //
+				.withMessageContaining("Invalid aggregation") //
+				.withMessageContaining("findByAggregation");
+	}
+
 	private MongoQueryMethod queryMethod(Class<?> repository, String name, Class<?>... parameters) throws Exception {
 
 		Method method = repository.getMethod(name, parameters);
@@ -404,6 +413,12 @@ public class MongoQueryMethodUnitTests {
 		Person findAndIncrementVisitsByFirstname(String firstname);
 	}
 
+	interface InvalidAggregationMethodRepo extends Repository<Person, Long> {
+
+		@Aggregation("[{'$group': { _id: '$templateId', maxVersion : { $max : '$version'} } }]")
+		List<User> findByAggregation();
+	}
+
 	interface Customer {
 
 	}