implement DescribedPredicate#negate()

overwriting `java.util.function.Predicate#negate()` to return a `DescribedPredicate`

Resolves #1480

Signed-off-by: Manfred Hanke <[email protected]>

Author: hankem

archunit/src/main/java/com/tngtech/archunit/base/DescribedPredicate.java

@@ -51,6 +51,15 @@ public String getDescription() {
         return description;
     }
 
+    /**
+     * @return A {@link DescribedPredicate} that will return {@code true} whenever this predicate would return {@code false}, and vice versa.
+     */
+    @Override
+    @PublicAPI(usage = ACCESS)
+    public DescribedPredicate<T> negate() {
+        return new NotPredicate<>(this);
+    }
+
     /**
      * Overwrites the description of this {@link DescribedPredicate}. E.g.
      *
@@ -176,7 +185,7 @@ public static <T> DescribedPredicate<T> doNot(DescribedPredicate<? super T> pred
 
     /**
      * @param predicate Any {@link DescribedPredicate}
-     * @return A predicate that will return {@code true} whenever the original predicate would return {@code false} and vice versa.
+     * @return A predicate that will return {@code true} whenever the original predicate would return {@code false}, and vice versa.
      * @param <T> The type of object the {@link DescribedPredicate predicate} applies to
      */
     @PublicAPI(usage = ACCESS)

archunit/src/test/java/com/tngtech/archunit/base/DescribedPredicateTest.java

@@ -200,19 +200,25 @@ public void describe_works() {
     @DataProvider
     public static Object[][] not_scenarios() {
         return $$(
-                $(new NotScenario("not") {
+                $(new NotScenario("not", ".negate") {
+                    @Override
+                    <T> DescribedPredicate<T> apply(DescribedPredicate<T> input) {
+                        return input.negate();
+                    }
+                }),
+                $(new NotScenario("not", "not") {
                     @Override
                     <T> DescribedPredicate<T> apply(DescribedPredicate<T> input) {
                         return not(input);
                     }
                 }),
-                $(new NotScenario("do not") {
+                $(new NotScenario("do not", "doNot") {
                     @Override
                     <T> DescribedPredicate<T> apply(DescribedPredicate<T> input) {
                         return doNot(input);
                     }
                 }),
-                $(new NotScenario("does not") {
+                $(new NotScenario("does not", "doesNot") {
                     @Override
                     <T> DescribedPredicate<T> apply(DescribedPredicate<T> input) {
                         return doesNot(input);
@@ -279,16 +285,18 @@ private Function<Object, Integer> constant(int integer) {
 
     private abstract static class NotScenario {
         private final String expectedPrefix;
+        private final String methodName;
 
-        NotScenario(String expectedPrefix) {
+        NotScenario(String expectedPrefix, String methodName) {
             this.expectedPrefix = expectedPrefix;
+            this.methodName = methodName;
         }
 
         abstract <T> DescribedPredicate<T> apply(DescribedPredicate<T> input);
 
         @Override
         public String toString() {
-            return expectedPrefix;
+            return expectedPrefix + " (via " +  methodName + ")";
         }
     }