GH-995 - Allow filtering violations.

spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModule.java

@@ -40,7 +40,6 @@ import org.springframework.lang.Nullable;
 import org.springframework.modulith.core.Types.JMoleculesTypes;
 import org.springframework.modulith.core.Types.JavaTypes;
 import org.springframework.modulith.core.Types.SpringTypes;
-import org.springframework.modulith.core.Violations.Violation;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 import org.springframework.util.function.SingletonSupplier;

spring-modulith-core/src/main/java/org/springframework/modulith/core/Violation.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.modulith.core;
+
+import java.util.Objects;
+
+import org.springframework.util.Assert;
+
+/**
+ * An individual architectural violation.
+ *
+ * @author Oliver Drotbohm
+ * @since 1.3.1
+ */
+public class Violation {
+
+	final String message;
+
+	Violation(String message) {
+		this.message = message;
+	}
+
+	/**
+	 * Returns the violation message.
+	 *
+	 * @return the message
+	 */
+	public String getMessage() {
+		return message;
+	}
+
+	/**
+	 * Returns whether the {@link Violation}'s message contains the given candidate.
+	 *
+	 * @param candidate must not be {@literal null} or empty.
+	 */
+	public boolean hasMessageContaining(String candidate) {
+
+		Assert.hasText(candidate, "Candidate must not be null or empty!");
+
+		return message.contains(candidate);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see java.lang.Object#toString()
+	 */
+	@Override
+	public String toString() {
+		return message;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see java.lang.Object#equals(java.lang.Object)
+	 */
+	@Override
+	public boolean equals(Object obj) {
+
+		return this == obj
+				|| obj instanceof Violation that
+						&& Objects.equals(this.message, that.message);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see java.lang.Object#hashCode()
+	 */
+	@Override
+	public int hashCode() {
+		return Objects.hashCode(message);
+	}
+}

spring-modulith-core/src/main/java/org/springframework/modulith/core/Violations.java

@@ -20,6 +20,7 @@ import static java.util.stream.Collectors.*;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.function.Predicate;
 import java.util.stream.Collector;
 import java.util.stream.Collectors;
 
@@ -57,7 +58,7 @@ public class Violations extends RuntimeException {
 	 * @return will never be {@literal null}.
 	 */
 	static Collector<String, ?, Violations> toViolations() {
-		return mapping(Violation::new, collectingAndThen(Collectors.toList(), Violations::new));
+		return mapping(Violation::new, newViolations());
 	}
 
 	/*
@@ -68,7 +69,7 @@ public class Violations extends RuntimeException {
 	public String getMessage() {
 
 		return violations.stream() //
-				.map(Violation::message) //
+				.map(Violation::getMessage) //
 				.collect(Collectors.joining("\n- ", "- ", ""));
 	}
 
@@ -81,7 +82,7 @@ public class Violations extends RuntimeException {
 	public List<String> getMessages() {
 
 		return violations.stream() //
-				.map(Violation::message)
+				.map(Violation::getMessage)
 				.toList();
 	}
 
@@ -104,6 +105,21 @@ public class Violations extends RuntimeException {
 		}
 	}
 
+	/**
+	 * Returns {@link Violations} that match the given {@link Predicate}.
+	 *
+	 * @param filter must not be {@literal null}.
+	 * @return
+	 */
+	public Violations filter(Predicate<Violation> filter) {
+
+		Assert.notNull(filter, "Filter must not be null!");
+
+		return violations.stream()
+				.filter(filter)
+				.collect(newViolations());
+	}
+
 	/**
 	 * Creates a new {@link Violations} with the given {@link RuntimeException} added to the current ones?
 	 *
@@ -142,14 +158,16 @@ public class Violations extends RuntimeException {
 
 		var result = new ArrayList<>(left);
 
-		var messages = left.stream().map(Violation::message).toList();
+		var messages = left.stream().map(Violation::getMessage).toList();
 
 		right.stream()
-				.filter(it -> !messages.contains(it.message()))
+				.filter(it -> !messages.contains(it.message))
 				.forEach(result::add);
 
 		return result.size() == left.size() ? left : result;
 	}
 
-	static record Violation(String message) {}
+	private static Collector<Violation, ?, Violations> newViolations() {
+		return collectingAndThen(Collectors.toList(), Violations::new);
+	}
 }

spring-modulith-core/src/test/java/org/springframework/modulith/core/ViolationsUnitTests.java

@@ -51,4 +51,14 @@ class ViolationsUnitTests {
 		assertThat(violations.getMessages())
 				.containsExactlyInAnyOrder("First", "Second", "Third");
 	}
+
+	@Test // GH-995
+	void allowsFilteringViolations() {
+
+		var violations = Violations.NONE.and("First").and("Second")
+				.filter(it -> it.hasMessageContaining("Sec"));
+
+		assertThat(violations.getMessages())
+				.containsExactly("Second");
+	}
 }