When returning multiple failures, eliminate any duplicate messages.

README.md

@@ -3,7 +3,7 @@
 
 # <img src="docs/checklist.svg" width=64 height=64 alt="checklist"> Requirements API
 
-[![API](https://img.shields.io/badge/api_docs-5B45D5.svg)](https://cowwoc.github.io/requirements.java/10.7/)
+[![API](https://img.shields.io/badge/api_docs-5B45D5.svg)](https://cowwoc.github.io/requirements.java/10.8/)
 [![Changelog](https://img.shields.io/badge/changelog-A345D5.svg)](docs/changelog.md)
 [![javascript, typescript](https://img.shields.io/badge/other%20languages-javascript,%20typescript-457FD5.svg)](../../../requirements.js)
 
@@ -22,7 +22,7 @@ To get started, add this Maven dependency:
 <dependency>
   <groupId>com.github.cowwoc.requirements</groupId>
   <artifactId>java</artifactId>
-  <version>10.7</version>
+  <version>10.8</version>
 </dependency>
 ```
 
@@ -152,14 +152,14 @@ This library offers the following features:
 Designed for discovery using your favorite IDE's auto-complete feature.
 The main entry points are:
 
-* [requireThat(value, name)](https://cowwoc.github.io/requirements.java/10.7/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/DefaultJavaValidators.html#requireThat(T,java.lang.String))
+* [requireThat(value, name)](https://cowwoc.github.io/requirements.java/10.8/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/DefaultJavaValidators.html#requireThat(T,java.lang.String))
   for method preconditions.
-  * [that(value, name)](https://cowwoc.github.io/requirements.java/10.7/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/DefaultJavaValidators.html#that(T,java.lang.String))
+  * [that(value, name)](https://cowwoc.github.io/requirements.java/10.8/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/DefaultJavaValidators.html#that(T,java.lang.String))
     for [class invariants, method postconditions and private methods](docs/features.md#assertion-support). 
-  * [checkIf(value, name)](https://cowwoc.github.io/requirements.java/10.7/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/DefaultJavaValidators.html#checkIf(T,java.lang.String))
+  * [checkIf(value, name)](https://cowwoc.github.io/requirements.java/10.8/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/DefaultJavaValidators.html#checkIf(T,java.lang.String))
     for multiple failures and customized error handling.
 
-See the [API documentation](https://cowwoc.github.io/requirements.java/10.7/) for more details.
+See the [API documentation](https://cowwoc.github.io/requirements.java/10.8/) for more details.
 
 ## Best practices
 

docs/changelog.md

@@ -2,6 +2,10 @@ Minor updates involving cosmetic changes have been omitted from this list.
 
 See https://github.com/cowwoc/requirements.java/commits/main for a full list.
 
+## Version 10.8 - 2025/01/13
+
+* When returning multiple failures, eliminate any duplicate messages. 
+
 ## Version 10.7 - 2025/01/03
 
 * Bugfix: If the string representation of the expected and actual values was equal, the class names were not

docs/features.md

@@ -130,7 +130,7 @@ String province = "Florida";
 List<String> provinces = Arrays.asList("Ontario", "Quebec", "Nova Scotia", "New Brunswick", "Manitoba",
   "British Columbia", "Prince Edward Island", "Saskatchewan", "Alberta", "Newfoundland and Labrador");
 
-List<ValidationFailure> failures = checkIf(name, "name").length().isBetween(10, 30).elseGetFailures();
+List<ValidationFailure> failures = new ArrayList<>(checkIf(name, "name").length().isBetween(10, 30).elseGetFailures());
 failures.addAll(checkIf(provinces, "provinces").contains(province).elseGetFailures());
 
 for (ValidationFailure failure: failures)
@@ -174,7 +174,7 @@ requireThat(nameToAge, "nameToAge").
 ## String diff
 
 When
-a [String comparison](https://cowwoc.github.io/requirements.java/10.7/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/type/component/ObjectValidatorComponent#isEqualTo(java.lang.Object))
+a [String comparison](https://cowwoc.github.io/requirements.java/10.8/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/type/component/ObjectValidatorComponent#isEqualTo(java.lang.Object))
 fails, the library outputs a diff of the values being compared.
 
 Depending on the terminal capability, you will see a [textual](textual_diff.md) or a [colored](colored_diff.md) diff.
@@ -188,7 +188,7 @@ terminal.
 
 The use of colors is disabled by default if stdin or stdout are redirected, even if ANSI colors are supported.
 To enable colors,
-invoke [GlobalConfiguration.terminalEncoding(TerminalEncoding)](https://cowwoc.github.io/requirements.java/10.7/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/GlobalConfiguration.html#terminalEncoding(com.github.cowwoc.requirements10.java.TerminalEncoding)).
+invoke [GlobalConfiguration.terminalEncoding(TerminalEncoding)](https://cowwoc.github.io/requirements.java/10.8/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/GlobalConfiguration.html#terminalEncoding(com.github.cowwoc.requirements10.java.TerminalEncoding)).
 
 ## Returning the value after validation
 

docs/supported_libraries.md

@@ -1,11 +1,11 @@
 Each module uses a separate class pair for validation. For example, 
-[DefaultJavaValidators](https://cowwoc.github.io/requirements.java/10.7/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/DefaultJavaValidators.html)
+[DefaultJavaValidators](https://cowwoc.github.io/requirements.java/10.8/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/DefaultJavaValidators.html)
 and
-[JavaValidators](https://cowwoc.github.io/requirements.java/10.7/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/JavaValidators.html)
+[JavaValidators](https://cowwoc.github.io/requirements.java/10.8/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/java/JavaValidators.html)
 validate the core Java API. Similarly,
-[DefaultGuavaValidators](https://cowwoc.github.io/requirements.java/10.7/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/guava/DefaultGuavaValidators.html)
+[DefaultGuavaValidators](https://cowwoc.github.io/requirements.java/10.8/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/guava/DefaultGuavaValidators.html)
 and
-[GuavaValidators](https://cowwoc.github.io/requirements.java/10.7/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/guava/GuavaValidators.html)
+[GuavaValidators](https://cowwoc.github.io/requirements.java/10.8/com.github.cowwoc.requirements.java/com/github/cowwoc/requirements10/guava/GuavaValidators.html)
 validate the Guava API.
 
 The following table lists validators for third-party libraries: 

java/src/main/java/com/github/cowwoc/requirements10/java/ValidationFailures.java

@@ -69,14 +69,7 @@ public boolean throwOnFailure()
 	{
 		if (failures.isEmpty())
 			return true;
-		Throwable throwable;
-		if (failures.size() == 1)
-		{
-			ValidationFailure failure = failures.getFirst();
-			throwable = failure.getException();
-		}
-		else
-			throwable = new MultipleFailuresException(failures);
+		Throwable throwable = getThrowable();
 		if (cleanStackTrace)
 			Exceptions.removeLibraryFromStackTrace(throwable);
 		switch (throwable)
@@ -87,6 +80,19 @@ public boolean throwOnFailure()
 		}
 	}
 
+	/**
+	 * @return the failure exception
+	 */
+	private Throwable getThrowable()
+	{
+		if (failures.size() == 1)
+		{
+			ValidationFailure failure = failures.getFirst();
+			return failure.getException();
+		}
+		return new MultipleFailuresException(failures);
+	}
+
 	/**
 	 * Returns the validation failure messages.
 	 *
@@ -115,14 +121,7 @@ public Throwable getException()
 	{
 		if (failures.isEmpty())
 			return null;
-		Throwable throwable;
-		if (failures.size() == 1)
-		{
-			ValidationFailure failure = failures.getFirst();
-			throwable = failure.getException();
-		}
-		else
-			throwable = new MultipleFailuresException(failures);
+		Throwable throwable = getThrowable();
 		if (cleanStackTrace)
 			Exceptions.removeLibraryFromStackTrace(throwable);
 		return throwable;

java/src/main/java/com/github/cowwoc/requirements10/java/internal/validator/AbstractValidator.java

@@ -158,6 +158,13 @@ public void addFailure(String message, Throwable cause, ExceptionBuilder excepti
 	{
 		ValidationFailureImpl failure = new ValidationFailureImpl(configuration, message, cause,
 			exceptionBuilder, Set.of());
+		for (ValidationFailure existingFailure : failures)
+			if (existingFailure.getMessage().equals(failure.getMessage()))
+			{
+				// Skip duplicate failure messages
+				return;
+			}
+
 		failures.add(failure);
 		if (configuration.throwOnFailure())
 		{
@@ -186,6 +193,13 @@ public <E extends Exception> void addFailure(String message, Throwable cause,
 	{
 		ValidationFailureImpl failure = new ValidationFailureImpl(configuration, message, cause, exceptionBuilder,
 			Set.of(checkedException));
+		for (ValidationFailure existingFailure : failures)
+			if (existingFailure.getMessage().equals(failure.getMessage()))
+			{
+				// Skip duplicate failure messages
+				return;
+			}
+
 		failures.add(failure);
 		if (configuration.throwOnFailure())
 		{

pom.xml

@@ -117,7 +117,7 @@
 			<dependency>
 				<groupId>ch.qos.logback</groupId>
 				<artifactId>logback-classic</artifactId>
-				<version>1.5.15</version>
+				<version>1.5.16</version>
 			</dependency>
 			<dependency>
 				<groupId>com.github.javaparser</groupId>
@@ -147,7 +147,7 @@
 			<dependency>
 				<groupId>org.twdata.maven</groupId>
 				<artifactId>mojo-executor</artifactId>
-				<version>2.4.1-m2</version>
+				<version>2.4.1</version>
 			</dependency>
 			<dependency>
 				<groupId>org.testng</groupId>
@@ -157,7 +157,7 @@
 			<dependency>
 				<groupId>org.assertj</groupId>
 				<artifactId>assertj-core</artifactId>
-				<version>3.27.1</version>
+				<version>3.27.2</version>
 			</dependency>
 		</dependencies>
 	</dependencyManagement>

test/src/test/java/com/github/cowwoc/requirements10/test/java/ComparableTest.java

@@ -715,9 +715,8 @@ public void multipleFailuresNullIsComparableTo()
 			TestValidators validators = TestValidators.of(scope);
 
 			Integer actual = null;
+			// Ensure that expectedMessages does not contain the same failure message twice
 			List<String> expectedMessages = List.of("""
-				"actual" must be equal to 5.
-				actual: null""", """
 				"actual" must be equal to 5.
 				actual: null""");
 			try (ConfigurationUpdater configurationUpdater = validators.updateConfiguration())